The development of the Periodic Table
Introduction
Ask most chemists who discovered the Periodic table and
you will almost certainly get the answer Dmtri Mendeleev.
Certainly Mendeleev was the first to publish a version of
the Table that we would recognise today but does he
deserve all the credit? What would have happened without
Mendeleev, and is it really appropriate to use the word
discovered?
No one can give definitive answers to these questions but
it is certainly true that a number of other chemists before
Mendeleev were investigating patterns in the properties of
the elements that were known at the time and it is surely
true that had Mendeleev never lived modern chemists
would be using a Periodic Table.
This material looks at the work of other chemists such as
John Newlands, Lothar Meyer and Alexandre-Emile
Béguyer de Chancourtois as well as Mendeleev himself in
developing the Periodic Table.
You may find other spellings of Mendelev’s name,
Mendeleyev, Mendelejeff, Mendeleeff or
Mendelayev, for example. There is no ‘correct’
spelling in English because the Mendeleev himself
would have spelt it using the Russian (cyrillic)
alphabet.
Some scientists, and many science fiction writers,
have speculated that the Periodic Table might be the
basis of communication with an alien civilisation if
the human race were ever to meet one. If we make
the reasonable assumption that the properties of the
elements are the same everywhere in the universe,
then it seems inevitable that a technologically
advanced race would have their own version of the
Periodic Table which would contain the same
information as ours (even if expressed very
differently).
John Newlands
Could the original formulation of the Periodic Table be regarded as British? Just four years
before Mendeleev announced his Periodic Table, John Alexander Reina Newlands (see box)
wrote in Chemical News
‘If the elements are arranged in order of their equivalents [ie relative atomic masses in
today’s terminology] with a few transpositions, it will be seen that elements belonging to the
same group appear in the same horizontal line. Also the numbers of similar elements differ by
seven or multiples of seven. Members stand to each other in the same relation as the
extremities of one or more octaves of music. Thus in the nitrogen group phosphorus is the
seventh element after nitrogen and arsenic is the fourteenth elements after phosphorus as is
antimony after arsenic. This peculiar relationship I propose to call The Law of Octaves'.
Surely this was a prediction of patterns in the properties of the elements and described a
Periodic Table?
Newlands thought that patterns were connected with the relative weights of atoms (we would
now call them relative atomic masses – they were then called atomic weights) of different
elements. Fortunately, in 1860 there had been a conference in Karlsruhe (Germany) which
had made a more accurate list of these atomic weights than had previously been available.
Not only had some values been slightly wrong through inaccurate measurements but some
were half or a third of the correct value through false reasoning. See box Problems with
relative atomic masses.
One difficulty was that only about 60 elements were known then (there are over 100 now),
although fortunately most of the undiscovered ones were of higher relative atomic mass.
Newlands listed those known in order of their atomic weight putting their position in this
sequence alongside the symbol. He did not give a name to this position number. A copy of his
table is shown below using the symbols Newlands used.
H1
F8
Cl 15
Co/Ni 22
Br 29
Pd 36
I 42
Pt/Ir 50
Li 2
Na 9
K 16
Cu 23
Rb 30
Ag 37
Cs 44
Tl 53
Gl 3
Mg 10
Ca 17
Zn 25
Sr 31
Cd 34
Ba/V 45
Pb 54
Bo 4
Al 11
Cr 18
Y 24
Ce/La 33
U 40
Ta 46
Th 56
C5
Si 12
Ti 19
In 26
Zr 32
Sn 39
W 47
Hg 52
N6
P 13
Mn 20
As 27
Di/Mo 34
Sb 41
Nb 48
Bi 55
O7
S 14
Fe 21
Se 28
Ro/Ru 35
Te 43
Au 49
Os 51
The pattern was perfect up to calcium then became less convincing as some metals
appeared unlike the non-metals to their left. However a further seven elements later there
was a greater similarity. Then Newlands was forced to sometimes put two elements in the
same box so that after this similar elements would be in the same horizontal line. Di stood for
didymium, which we now know is not an element at all but a mixture of two elements.
Note that Newlands did not always stick to a strict increase in number. He exchanged the
positions of Zn and Y, presumably because he realised that Y resembled Bo (modern symbol
B). The modern Periodic Table does not always show an increase in relative atomic masses
for successive elements but it is a less common occurrence than in Newlands’ table.
On 1st March 1865, he described his ideas at a lecture at the Chemical Society (a forerunner
of the Royal Society of Chemistry). The lack of spaces for undiscovered elements and the
placing of two elements in one box were justifiably criticised but an unfair suggestion from
Professor Foster was that he might have equally well listed the elements alphabetically.
Foster was on the Publication Committee which refused to publish his paper, supposedly
because it was of a purely theoretical nature. Humiliated, Newlands went back to his work as
chief chemist at a sugar factory.
John Newlands
Newlands was British - his father was a
Scottish Presbyterian minister. His unusual
third name, was a family name showing his
mother's Italian roots, indeed he fought on
Garibaldi's side during the campaign to reunify
Italy. He was born in London on 26th November
1837.
He was educated by his father at home rather
than at school then studied for a year (1856) at
the Royal College of Chemistry which is now
part of Imperial College London. Later he
worked at an agricultural college trying to find
patterns of behaviour in organic chemistry.
However he is more remembered for his search
for a pattern in inorganic chemistry.
John Newlands. Reproduced courtesy of the Library and
Information Centre, Royal Society of Chemistry.
The house where Newlands was born, at 19, West Square,
London, near the Elephant and Castle underground station.
Reproduced courtesy of Gordon Woods.
Four years later Mendeleev, unaware of Newlands' ideas, formulated an improved Periodic
Table which gained acceptance, particularly because he left spaces for undiscovered
elements, some of which were soon found with properties he predicted. As the Periodic Table
became accepted, Newlands, understandably, claimed its first publication. However the
Chemical Society did not back his claims. Indeed the final years of his working life were spent
running a family chemical business with his brother.
The Chemical Society made some amends for discrediting him by asking him in 1884 to give
a lecture on the Periodic Law. However its full recognition of his discovery waited until 1998,
the centenary of his death, when the Royal Society of Chemistry oversaw the placing of a
blue commemorative plaque on the wall of his birthplace. Note its inscription.
Reproduced courtesy of Gordon Woods
Problems with relative atomic masses
What was the faulty reasoning that led to inaccurate relative atomic masses (atomic weights)?
There were two main faults. First chemists were not distinguishing between the weights of
atoms and of molecules. Seven common elements exist as diatomic molecules (molecules
containing two atoms, such as oxygen, O2), of special importance being hydrogen, the original
standard for atomic weights. If a molecule of H2 is given a relative mass of 1 instead of 2, then
when other elements are compared with it, their relative atomic masses are halved.
Second, at the time chemists used a term called equivalent, or combining weight. This was
the number of grams of an element that combined with 8 g of oxygen (They used this
because 8 g of oxygen combine with 1 g hydrogen so 8 g of oxygen was equivalent to 1 g
hydrogen.) Chemists used this because it is in general easier practically to measure the
weight of an element that combines with oxygen than the weight that combines with
hydrogen. Atomic weights were then found from the equivalent weight using the relationship:
Equivalent weight x valency = atomic weight
where valency is the combining power of an element (the number of atoms of hydrogen that
would combine with an atom of the element).
For example the equivalent weight of carbon is 3 g, because 3 g of carbon combine with 8 g
oxygen. The valency of carbon is 4 because it forms the compound methane, CH 4. So the
relative atomic mass of carbon is 3 x 4 = 12.
Even when the equivalent weight was accurately determined, if the valency was wrong then a
simple fraction of the correct atomic weight was obtained. (In the above example, if the
valency of carbon was thought to be two, the value for carbon’s atomic weight would be 6.)
The combining (or equivalent) weights were generally accurate but sometimes an element
was given the wrong valency. Thus beryllium, combining weight 4.6, was given the valency 3
because it was chemically similar to aluminium. This gave an atomic weight of 13.8, placing it
between carbon and nitrogen where there was no space.
Questions
Q 1.
Newlands was the first person to give elements a 'position number'.
(a) What do we call this today?
(b) What property of the atomic nucleus is it related to?
Q 2.
(a) Which modern chemical group is missing from Newlands’ list of elements?
(b) Apart from the omission of this whole group which element is the first omitted?
Q 3.
There are some unfamiliar symbols. Give the modern symbols and names of Gl and
Bo.
Q 4.
Give the symbols of two elements which are at least two columns out of position
because of extremely inaccurate atomic weights.
Q 5.
What do columns in the Newlands’ table almost correspond to in a modern Periodic
Table?
Q 6.
Where do the alkali metals Li, Na, K etc appear in Newlands’ table? Give the names of
the extra elements mixed with them. Why do you think Newlands thought they had a
similarity with the alkali metals? (Hint; what important property do elements in the
same group share?)
Q 7.
A musical octave goes from a note in one octave to the corresponding note in the next
octave, eg from C to C, counting the notes at both ends. How many elements are
there between Li and Na, or Na and K? What should this figure be? Explain the
difference.
Q 8.
Give two ways in which the Newlands’ table is inferior to that of Mendeleev.
Julius Lothar Meyer – the first identifier of
periodicity?
Most people regard Mendeleev as the initial formulator of the Periodic Table with the work of
his contemporaries often ignored. One such chemist was the German Julius Lothar Meyer,
(1830 - 1895), see box, who was just four years older than the Russian.
In 1864, five years before the first announcement of a Periodic System by Mendeleev, Meyer
had produced a table of just 28 elements which he listed by their valence. [The term valence
is now called valency and represents ‘combining power’ of an element. For example sodium
forms a chloride NaCl and has a valency of one; magnesium forms MgCl2 and has a valency
of two and so on.] The 28 elements were almost entirely main group elements. He
incorporated transition metals in another table in 1868 which listed the elements in increasing
weight order with elements with the same valence in a given column. This was earlier than
Mendeleev's table (1869) but unfortunately Meyer's was not published until 1870.
Mendeleev and Meyer were unaware of each other’s work until after this. Later, Meyer
admitted that the Russian had first published about the Periodic System by saying that his
ideas matched those of Mendeleev.
However Meyer’s main contribution was his recognition of periodic behaviour, ie a repeating
pattern of a property shown on a graph. In the case of Meyer, the property he chose was the
atomic volume of an element and he plotted against its atomic weight.
The graph below clearly shows a periodic pattern as the atomic volume rises to peaks and
then falls again.
Atomic volume is the volume of a mole of atoms (using modern terminology) and is therefore
a measure of the size of an atom of a particular element provided that the element is in the
solid state where the atoms are packed closely together.
Julius Lothar Meyer
Meyer and Mendeleev had a great deal in
common. They both attended the crucial first world
chemistry conference at Karlsruhe which produced
a significantly more accurate list of atomic weights
than had previously existed. This was the key to
arranging the elements in sequence. They both
trained at Heidelberg University under Bunsen and
Kirchoff. Thus they would certainly have known
each other although neither was aware of all the
work done by the other. Meyer's roots, however,
were firmly in Germany.
Julius Lothar Meyer . Reproduced courtesy of the Library
and Information Centre, Royal Society of Chemistry.
Activity
You can investigate Meyer’s graph using a spreadsheet. The data on the spreadsheet
that accompanies the web site is modern and is therefore more accurate than that
which Meyer had. It also includes the elements discovered since Meyer’s time. You could
eliminate these by using the interactive Periodic Table to find which elements were
known in Meyer’s time (1868). You can use the spreadsheet to calculate the atomic
volume of each element and then to plot this quantity against relative atomic mass. You
should also omit from your graph elements that are not in the solid state at room
temperature. This is because in liquids and especially in gases, the atoms are not packed
closely together so the volume of a mole of atoms does not tell us much about the size
of the atoms of an element (it actually tells us about the spacing between them).
Questions
Q 9.
What is the valency of the metal in the following compounds: CrCl2, CrCl3, TiCl2,
TiCl4?
Q 10. What sorts of elements are at the peaks of Meyer’s graph?
Q 11. Explain why oxygen, nitrogen and fluorine are missing from Meyer’s graph.
Alexandre-Emile Béguyer de Chancourtois
Can France claim the first Periodic Table? Probably not, but a French Geology Professor
made a significant advance towards it even though at the time few people were aware of it.
How did this happen?
All Periodic Tables list the elements in order of a particular property. A property which can be
expressed by a number (such as relative atomic mass) is better than a property which cannot
(such as colour). In 1860 a conference was held in Karlsruhe (Germany) which produced a
much more accurate list of atomic weights than previously available. (Not only were some
earlier values slightly inaccurate, faulty reasoning had led to some being a half or a third of
the correct value). See the box Problems with relative atomic masses. Alexandre Béguyer de
Chancourtois, see box, was the first person to list the known elements in order of increasing
weight of their atoms.
In 1862, before Newlands announced his Law of Octaves and Mendeleev described his
Periodic System, de Chancourtois presented a paper to the French Academy of Sciences
which was then published in Comptes Rendus, their in-house journal. Even for French
speakers it was difficult to understand and the diagram (below left) which would have made
his ideas much clearer was omitted although it did later appear in a less widely-read
geological pamphlet. It is not surprising then, that chemists in other countries were unaware
of his ideas. Indeed they were unrecognised until after Mendeleev's more detailed ideas of a
Periodic Table had become accepted and de Chancourtois belatedly pointed out his
contribution.
de Chancourtois called his idea vis tellurique or telluric spiral because the element tellurium
came in the middle. It was also somewhat appropriate coming from a geologist as the
element tellurium is named after the Earth. He plotted the atomic weights on the outside of a
cylinder such that one complete turn corresponded to an atomic weight increase of 16. The
redrawn image (below right) shows only the first two turns which have been unwound.
Note that similar elements appear in the same vertical line. Elements in the same vertical line
have atomic weights which differ by 16. For example, lithium's atomic weight is 7, sodium’s is
7 + (16 x 1) = 23 and potassium’s 7 + (16 x 2) = 39. Mathematically these obey the equation:
atomic weight = 7 + 16n where n is a whole number.
In general if m is the atomic weight of the element in the first spiral, then the atomic weights of
similar elements are given by
atomic weight = m + 16n
The graph used this table of values.
Element symbol Atomic weight
H
1
Li
7
Gl
9
Bo
11
C
12
Az
14
O
16
NH4
18
Na
23
Mg
24
Al
27
Si
28
Ph
31
S
32
Cl
35
K
39
Ca
40
Ti
48
V
51
Cr
52
Mn
55
Fe
56
The graph is effectively atomic weight against atomic weight at an angle of 45º, so no wonder
it is a perfect straight line despite any inaccuracy in the data.
Alexandre Béguyer de
Chancourtois
Alexandre Béguyer de Chancourtois was a geologist
who led several overseas expeditions and was
Inspector of Mines in Paris. This was at a time when
scientists specialised much less than they do today.
In his role as mines inspector he introduced laws to
improve safety in mines to prevent explosions of
firedamp (methane gas).
Alexandre Béguyer de Chancourtois. Reproduced
courtesy of Annales des mines, Paris.
Activity
Use graph paper, or a graphics programme to draw a complete telluric spiral as far as
iron. You could then roll this into a cylinder to form a replica of what de Chancourtois
described.
Questions
Q 12. List the seven common elements that exist as diatomic molecules, X2.
Q 13. Some of the symbols used in the telluric spiral differ from those used in the modern
Periodic Table.
(a) Gl stands for glucinium. What is this element called today?
(b) Az is short for azote, meaning 'without life'.
(i) What is the English name of this element?
(ii) Give a reason either for or against the meaning 'without life'.
(c) Which other two element symbols differ from those used today? In both cases give
the name, old and new symbols.
(d)
(i) What is the name of NH4
(ii) Why should it not be on the graph?
Q 14. (a) Use the formula atomic weight = 7 + 16n to check whether the three elements in
the vertical column Gl, Mg and Ca fit the pattern.
(b) What word is used today for such a vertical column of elements?
(c) What common feature do these elements have in their electron shells?
(d)
(i) Which element has an atomic weight 16 more than Ca?
(ii) It is not placed below Ca in modern tables. Suggest why not.
Q 15.
de Chancourtois listed elements in order of increasing atomic weight (relative atomic
mass).
(a) In what order are they placed in a modern Periodic Table?
(b) Find two examples of where these two orders differ.
Q 16.
Which complete family of elements is omitted because it had not yet been
discovered?
Dmitri Mendeleev
What is a mark of a great scientist? Good scientists discover new information and make
sense of it, linking it to other data. They may go further by giving an explanation of this linked
data which, maybe not immediately, other scientists accept as a correct explanation. However
the outstanding scientist goes further in predicting consequences of his ideas which can be
tested. This boldness identifies the great scientist if the predictions are later found to be
accurate. One such person was Russian chemist Dmitri Mendeleev, see box. Incidentally,
although he is often regarded as the father of the Periodic Table, Mendeleev himself called
his table, or matrix, the Periodic System.
Dmitri Mendeleev
Mendeleev was born at Tobolsk in 1834, the
youngest child of a large Siberian family. After his
father's death his mother, recognising how bright
her son was, brought the family 1500 km west to St
Petersburg, capital of Czarist Russia, where she
managed to get Dmitri into 'a good school'. She
died soon after but Dmitri was keen to fulfil his
mother's ambitions for him. After school he trained
as a science teacher and despite missing time
through illness he came top of his year. His first job
(1855) was on the Crimean peninsula, where the
climate was better for this health. However he soon
left the classroom and began accumulating
information while doing university research in
France and Germany. Rapidly climbing the
academic ladder in 1864 he was appointed
chemistry professor back in St Petersburg. As he
could not find a satisfactory Russian textbook, he
wrote his own - Chemical Principles.
He worked long hours, living next to his place of
work. Maybe he was an absentee father much of
the time. He cared little for his appearance and only
trimmed his beard once each spring ... he did not
even smarten up when he met the Czar himself! He
was politically left wing, a supporter of the working
class. He had some radical ideas which eventually
offended the university authorities leading to the
loss of his professorship.
Dmitri Mendeleev. Reproduced courtesy of the Library
and Information Centre, Royal Society of Chemistry.
Formulator of the Periodic
Table
Other people, like Londoner John
Newlands, Frenchman Alexandre
Béguyer de Chancourtois and German
Julius Lothar Meyer made important
contributions to the first Periodic Table
but the main credit goes to Mendeleev.
All of them were helped by the
publication in 1860 of more accurate
atomic weights, as relative atomic
masses were then called. There were
two main problems about establishing
a pattern for the elements. First only
about 60 elements had been
discovered (we now know of over 100)
and second some of the information
about the 60 was wrong. It was if
Mendeleev was doing a jigsaw with
one third of the pieces missing, and
other pieces bent!
Mendeleev had written the properties
of elements on pieces of card and
tradition has it that after organising the
cards while playing patience he
suddenly realised that by arranging the
element cards in order of increasing
atomic weight that certain types of
element regularly occurred. For
A commemorative stamp collector’s miniature
example a reactive non-metal was
sheet showing some of Mendeleev’s original
directly followed by a very reactive
notes. Horizontal lines like Cr, Mo and W (in the
light metal, then a less reactive light
third row down) correspond to today's groups.
metal. The image of a stamp
Note the date, 17 February 1869.
collectors’ miniature sheet shows a
stamp commemorating the hundredth
anniversary of the Periodic Table superimposed on some of Mendeleev’s original jottings.
Shortly after, his ideas were presented to the Russian Physico-chemical Society. They were
read by Professor Menschutkin because Mendeleev was ill. His ideas were then published in
the main German chemistry periodical of the time, Zeitschrift fϋr Chemie.
The world’s first view of Mendeleev’s Periodic Table – an extract from Zeitschrift fϋr
Chemie, 1869. See below for a translation
Concerning the relation between the properties and atomic weights of elements. By D.
Mendeleev. Arranging the elements in vertical columns with increasing atomic weights, so that the
horizontal rows contain similar elements, again in increasing weight order, the following table is obtained
from which general predictions can be drawn
1. Elements show a periodicity of properties if listed in order of size of atomic weights.
2. Elements with similar properties either have atomic weights that are about the same (Pt, Ir, Os)
or increase regularly (K, Rb, Cs).
3. The arrangement of the elements corresponds to their valency, and somewhat according to
their chemical properties (eg Li, Be, B, C, N, O, F).
4. The commonest elements have small atomic weights.
It continues ....
5. The value of the atomic weight determines the character of the element.
6. There are unknown elements to discover eg elements similar to Al and Si with atomic weights
in range 65-75.
7. The atomic weights of some elements may be changed from knowing the properties of
neighbouring elements. Thus the atomic weight of Te must be in range 123-126. It cannot be
128.
8. Some typical properties of an element can be predicted from its atomic weight.
What were the special features of Mendeleev's Periodic Table?
Why is Mendeleev considered to be the ‘father’ of the Periodic Table whilst others, such as
Newlands, Meyer and De Chantcourtois are considered to be also-rans?
First he put elements into their correct places in the table. In some cases the relative atomic
mass had been wrongly calculated by others. By correcting the relative atomic mass he put
the element in the correct place.
At the time, relative atomic masses (then called atomic weights) were laboriously determined
using the formula
atomic weight = equivalent weight x valency
The combining (or equivalent) weights (see box Problems with relative atomic masses) were
generally accurate but sometimes an element was given the wrong valency. Thus beryllium,
combining weight 4.6, was given the valency 3 because it was chemically similar to
aluminium. This gave an atomic weight of 13.8, placing it between carbon and nitrogen where
there was no space. Mendeleev said the valency was 2; the problem was solved - it fitted into
the space between lithium and boron.
Secondly, Mendeleev sometimes decided that atomic weights must be wrong because the
elements simply appeared in the wrong place. For example he placed tellurium before iodine
although its atomic weight is greater simply because iodine’s properties are so similar to
those of fluorine, chlorine and bromine and tellurium’s to those of oxygen, sulfur and selenium
rather than the other way round. We now know that it is atomic number, not relative atomic
mass that governs an element’s position in the Periodic Table but in most cases the two result
in the same order.
Correct predictions
The greatness of Mendeleev was that not only did he leave spaces for elements that were not
yet discovered but he predicted properties of five of these elements and their compounds.
How foolish he would have seemed if these predictions had been incorrect but fortunately for
him three of these missing elements were discovered by others within 15 years (ie within his
lifetime). The first of these Mendeleev had called eka-aluminium because it was the one after
aluminium (eka = 1 in Sanskrit) and was identified in Paris (1875) by Paul Emile Lecoq de
Boisbaudran who named it gallium after the Latin name for France. Mendeleev was ecstatic
when he heard of its properties which nearly matched his eka-aluminium. However de
Boisbaudran's value for gallium's density (4.9 g/cm3) differed from Mendeleev's prediction.
Mendeleev told the Frenchman, who re-measured the density to find Mendeleev was right! It
is interesting to speculate whether de Boisbaudran was pleased or irritated by this. The table
compares Mendeleev's predictions with de Boisbaudran's discovery.
Eka-aluminium (Ea)
Gallium (Ga)
Atomic weight
About 68
69.72
Density of solid
6.0 g/cm3
5.9 g/cm3
Melting point
low
29.78oC
Valency
3
3
Method of discovery
Probably from its spectrum
Spectroscopically
Oxide
Formula Ea2O3, density
5.5 g/cm3. Soluble in both
acids and alkalis.
Formula Ga2O3, density
5.88 g/cm3. Soluble in both
acids and alkalis.
Within the next ten years Swede Lars Nilson (1879) identified scandium, predicted by
Mendeleev as eka-boron and German Clemens Winkler (1886) discovered germanium which
he realised was Mendeleev's eka-silicon. These discoveries established the acceptance of
the Russian's table, although two other elements whose properties were predicted were not
discovered for 50 years.
One thing that Mendeleev did not predict was the discovery of a whole new Group of
elements, the noble gases, by the Scot William Ramsay and co-workers during the last
decade of the 19th century (see The discovery of new elements). Mendeleev was at first
dismayed by this but before he died in 1907 realised that Ramsay's discoveries were further
proof of the Periodic Table, not a contradiction. Ramsay was awarded a Nobel Prize for
discovering five elements. Mendeleev never received that honour However, an element,
atomic number 101, has been named after Mendeleev, an even rarer distinction. This is
surely deserved by the original formulator of the Periodic Table.
Questions
Q 17.
Mendeleev listed elements in order of increasing atomic weight (now called relative
atomic mass).
(a) What property is used today for the order of the elements?
(b) Which particle within the atom is responsible for this property?
Q 18.
Give one similarity and one difference between the tables produced by Newlands and
Mendeleev.
Q 19.
Give two examples of 'a reactive non-metal followed by a reactive light metal then a
less reactive light metal'.
Q 20.
Beryllium is chemically similar to aluminium.
(a) Suggest the appearance of beryllium oxide.
(b) What would be the formula of this oxide if it was similar to aluminium oxide?
(c) What is the correct formula?
Q 21. (a) What feature is common to the names of the three elements discovered within
Mendeleev’s lifetime?
(b) Mendeleev has an element named after him. Give the other elements named after
scientists.
Q 22.
Reproduced courtesy of Gordon Woods
The photograph shows a giant wall Periodic Table erected in St Petersburg, Russia, in
1934.
(a) Why was that year chosen for this giant memorial table?
(b) Elements in black were discovered between Mendeleev's death and 1934.
(i) How many are there?
(ii) Where are most of these elements placed in most Periodic Tables?
(c) There are still some blanks. Give the names and symbols of the alkali metal and
halogen still to be discovered.
(d) What are the normal symbols for the elements J and Jr?
(e) At the bottom of the columns are general formulae for the oxides and hydrides of
elements in that column. Look carefully and state the difference between them and
the normal way of writing their formulae.
Answers to questions
Q 1.
(a) Atomic number
(b) The number of protons
Q 2.
(a) The noble gases
(b) Scandium
Q 3.
Gl is beryllium (Be), Bo is boron (B)
Q 4.
Uranium (U) and vanadium (V)
Q 5.
Periods
Q 6.
They are in the same horizontal row. After K, they are only every other element as Cu,
Ag and Tl come in between. Like the alkali metals, these three elements can all form
ions with one positive charge.
Q 7.
Six. There are seven in the modern Periodic Table because of the discovery of the
noble gases.
Q 8.
It does not leave spaces for undiscovered elements. Sometimes two elements are
placed in the same box. There are more occasions in Newlands’ table where the
order of the elements does not correspond to the atomic mass order than in
Mendeleev’s table.
Q 9.
1, 2, 3, 4
Q 10. Alkali metals.
Q 11. They are all gases and could not have been cooled enough to solidify them in Meyer’s
day.
Q 12.
Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine.
Q 13. (a) Beryllium
(b) (i) Nitrogen.
(ii) All living things need nitrogen compounds to live and grow (nitrogen is found in all
proteins) but the gas nitrogen would suffocate us if breathed in without any oxygen as
well.
(c) Bo for boron is now replaced by B; Ph for phosphorus is now replaced by P.
(d) (i) Ammonium
(ii) It is not an element as it contains two elements, nitrogen and hydrogen.
Q 14. (a) Yes they do, more or less:
Gl atomic weight = 7 + 16n = 7+16 x 0 = 7
Mg atomic weight = 7 + 16n = 7+16 x 1 = 23
Ca atomic weight = 7 + 16n = 7+16 x 2 = 39
(b) Group
(c) They all have two electrons in their outer shells
(d) (i) Iron
(ii) It is a transition metal
Q 15. (a) Atomic number
(b) Iodine and tellurium, cobalt and nickel, and argon and potassium
Q 16. The noble gases
Q 17. (a) Atomic number.
(b) Number of protons.
Q 18.
Similarity: elements arranged in increasing weight order, elements with similar
properties recurred regularly
Difference: unlike Newlands Mendeleev left gaps for elements whose properties he
predicted, Newlands put two elements into some boxes unlike Mendeleev
Q 19.
F, Na, Mg and Cl, K, Ca. Remember that the noble gases had not been discovered at
this time.
Q 20. (a) White solid.
(b) Be2O3.
(c) BeO
Q 21. (a) Named after countries or group of countries (Gaul is an old name for France).
(b) Curium, Einsteinium, Fermium, Nobelium, Lawrencium, Rutherfordium, Bohrium,
Seaborgium and Meitnerium.
Q 22. (a) This was the centenary of Mendeleev's birth.
(b) (i) 17
(ii) Mostly lanthanides which are found in a block at the bottom of most tables.
(c) Alkali metal Fr Francium. Halogen At Astatine
(d) I (iodine) and Ir (iridium)
(e) The giant table has the number of atoms written as a superscript not a subscript, ie
above not below the symbol.