1.1 Periodic Table
Learning Outcomes
• History of the idea of elements,
• The contributions of the Greeks, Boyle, Davy
and Moseley.
Greek Periodic Table
Robert Boyle
• Element cannot be
split up into simpler
substances by
chemical means
Humphrey Davy
• Used electrolysis to
break down water
into hydrogen and
oxygen. Isolated
potassium and
sodium.
Henry Mosely
• Measured No.of
protons in the
nuclei of atoms.
Atomic number
to arrange
elements.
Dobereiner
• Saw trends and similarities among several
groups of elements in threes
• Triads = groups of 3 elements
• Chlorine = 35.5, Bromine = 80, Iodine = 127
(average of Cl and I = 81)
Newlands
• Tried to find some mathematical relation
between the atomic weights of elements
which were chemically similar
• Groups called octaves
• Arranged the elements in rows of seven
• Eighth element had properties similar to
the first
“Law of Octaves” because of its
similarity to musical octaves
Li
Be
B
C
N
O
F
Na
Mg
Al
Si
P
S
Cl
K
Ca
?
?
As
Se
Br
Mendeleev
Dimitri Mendeleev
• He suggested that the properties of the
elements were a function of their atomic
masses
• Left gaps for undiscovered elements
• Gave a name and predicted the properties of
these yet to be discovered elements.
Mendeleev’ s Table
Learning Outcomes
• Elements. Symbols of elements 1–36.
• The periodic table as a list of elements
arranged to demonstrate trends in their
physical and chemical properties.
• Brief statement of the principal resemblances
of elements within each main group, in
particular alkali metals, alkaline earth metals,
halogens and noble gases.
Modern periodic table
• Elements in the periodic table are arranged in
periods (rows) and groups(columns). Atomic
number increases as you move across a row
or period.
Modern periodic table
Periods
• The period number of an element signifies the
highest unexcited energy level for an electron
in that element.
Groups
• Elements within a group share several common
properties.
• Groups are elements have the same outer electron
arrangement.
• The outer electrons are called valence electrons.
Because they have the same number of valence
electrons, elements in a group share similar chemical
properties.
• The Roman numerals listed above each group are the
usual number of valence electrons. For example, a
group VA element will have 5 valence electrons.
Classifying Elements- Metals
Metals
•Metals are lustrous (shiny),
malleable (can be hammered)
• are good conductors of heat and
electricity.
Group 1: Alkali Metals
Group 1: Alkali Metals
The alkali metals are located in Group IA
(Sodium and potassium are examples of
these elements.
Alkali metals form salts and many other
compounds.
These elements are less dense than
other metals, form ions with a +1
charge, and have the largest atom sizes
of elements in their periods. The alkali
metals are highly reactive.
Alkaline Metals 1
Learning outcome
Demonstration of the
reaction with water of
lithium, sodium
and potassium.
Alkali metals
•
•
•
•
•
•
Group 1
Very reactive
Low density
Soft-can be cut with a knife
Burn in air to form oxides
React with water to form hydroxides
Sodium
• Sodium + Oxygen  Sodium oxide
• Sodium + Water  Sodium Hydroxide +
Hydrogen gas
• Stored in oil to prevent them from reacting
with air or water
Group 2: Alkaline Earth Metals
The alkaline earths are located in
Group IIA (second column) of the
periodic table.
Calcium and magnesium are
examples of alkaline earths. These
metals form many compounds.
They have ions with a +2 charge.
Their atoms are smaller than
those of the alkali metals.
Alkaline Earths
•
•
•
•
•
Group 2
Reactive
Harder than group one
Burn in air to form oxide
React with water to form hydroxides
Beryllium
Barium
calcium
Magnesium
Strontium
Radium
Group 17: Halogens
The halogens are located in Group
VIIA of the periodic table.
Examples of halogens are chlorine
and iodine. You find these
elements in bleaches,
disinfectants, and salts. These
nonmetals form ions with a -1
charge. The physical properties of
the halogens vary. The halogens
are highly reactive.
Halogens
•
•
•
•
Group 7
Reactive
Chlorine, Bromine, Iodine
React with hydrogen to form acids
Chlorine
• Green gas
• Chlorine + Hydrogen  Hydrogen Chloride gas
• Hydrogen chloride gas dissolves in water to
form Hydrochloric acid.
• Chlorine reacts with sodium to form Sodium
Chloride [Table Salt]
bromine
iodine
Group 18: Noble Gases
The noble gases are located in Group
VIII of the periodic table. Helium and
neon are examples of noble gases.
These elements are used to make
lighted signs, refrigerants, and lasers.
The noble gases are not reactive. This is
because they have little tendency to
gain or lose electrons.
Transition metals
Transition Metals
•The transition elements are
located in groups IB to VIIIB.
•These elements are very hard, with
high melting points and boiling
points. The transition metals are
good electrical conductors.
•They form positively charged ions.
nonmetals