10
ATOMS, MOLECULES
AND IONS
Learning Outcomes
Candidates should be able to:
Knowledge. Understanding and Application
(a)
describe
an atom as an
electrically neutral entity made up of a positively charged nucdeus (protons and
neutrons) with negatively charged electrons moving round the nucleus.
that atoms of the same element contain the
different elements contain different numbers of protons.
(6)show
an awareness
(c)
recognise that an ion is formed when
(d)
show
an
an
gains
atom
or
loses
number of protons and those of
same
electron(s).
understanding of the following:
fixed number of the
that molecules of an element consist of a
same
type of atoms combined together.
atoms combined together
consist of a fixed number of different types of
that molecules of a compound
(e)
state
the chemical formula of
the number and types of atoms, given
a
compound.
Skills and Processes
atom to other objects.
the relative size of an
(a)
compare
(6)
and molecules.
compare atoms
Ethics and Attitudes
ta)
show an appreciation
are
0
used to
probe n e w phenomena
show an appreciation
explain the
value
of
revised as
and continuously
constructed, justified
models are
how in practice,
additional data.
and collect
of scientific
fundamental nature
attitudes
such
of things and
and working in
individual effort
as
creativity and
to
the willingness
as
a team
part
ofscientific
openmindedness
re-examine
existing
in creating
they
models to
models.
inquiry.
10
atoms, molecules and ions
10-2
Atoms, molecules and ions
MCQs
062210-01
An atom is electrically neutral when
(A) the number of protons and electrons are equal in an atom.
(B) the number of protons and neutrons are equal in an atom.
(C)the number of electrons and neutrons are equal in the nucleus.
(D) the number of electrons and protons are equal in the nucleus.
06ZZ10-02
The chemical
properties of an
atom are
dependent on the number and arrangement of
(A) protons
(B) electrons
(C) neutrons
(D) nucleus
06ZZ10-03
Which of the following gases below has more than one kind of atom present in it?
(A) Water vapour
(B) Chlorine gas
(C) Helium gas
(D) lodine gas
|06ZZ10-04
The chemical formula of a compound will not indicate the
(A) number of atoms present in a molecule of the compound.
(B) elements present in each molecule of the compound.
(C) ratio of atoms present in each molecule of the compound
(D) size of each molecule of the compound.
them
Science Drill Questions
10-3
072210-05
Which substance
has the most
number of atoms?
(A) CaCO
(B) CH,C/
(C) KSO4
(D) CeHs
077710-06
Which of the following statements is false?
(A) The Periodic Table contains symbols of all the molecules.
(B) The chemical formula for ammonia is NHa.
(C)
Molecules
are
made up of atoms.
(D) Compounds with the same elements but different ratio of the elements have different properties.
072Z10-07
The element calcium has an atomic number of 20. This means that each calcium atom has,
(0) 20 electrons
(1) 20 protons
(1) 20 neutrons
(IV) 20 protons and neutrons
(A) land I
(8) Iand IlI
(C)I,1l and ll
(D) 1, Il and IV
072Z10-08
0.O element
A
If each of the
dgrams represents the molecule of
symbols
which
represents different kinds of atoms,
one
of the
following
an
(A)
(B)
C)
(D)
10
atoms, molecules and ions
10-4
07ZZ10-09
The compound calcium carbonate is represented by
Ca
Which of the following statements about calcium carbonate molecule are true?
(1)
The molecule contains three elements.
(11) The molecule contains three oxygen molecules.
(1) There are five atoms in the molecule.
(IV) The elements present in this molecule are calcium, carbon and oxygen.
(A) land
(B) Il and IV
(C) 1, Il and IV
(D) I, Il and IIl
06ZZ10-10
Which of the following diagrams shows a mixture of two elements?
(A)
(B)
CO
8
(C)
Sclence Drill Questions
(D)
10-5
06210-11
An
atom
number
of
utrons is
number
of
utrons is
(A) the
(B) the
of an element has no
electric
charge because
equal to the number of electrons.
equal to the number of protons.
t h e number of electrons is equal to the number of protons.
(D) t he number of electrons is equal to the number of protons and neutrons.
062210-12
The diagram on the right represents an atom of an element.
e
Key
e-electron
5n
n-neutron
4p
p-protons
Which symbol provides information on the atom?
(A)
9
(B)
Be
C
4
F
9
(D)
B
13
8
5
062710-13
What is the atomic structure of the Zion in which Z has atomic number 8 and mass number 18?
Electrons
Protons
Neutrons
(A)
8
8
8
8)
8
8
10
C)
8
8
18
(D)
10
8
10
062210-14
otopesare different ator with the same number of
A)
electrons, orotons and neutrons.
B) electrons but
different numbers of protons.
neutrons but different numbers of protons.
0protons but different numbers of neutrons.
10
atoms, molecules and ions
10-6
06ZZ10-15
5
How many atoms are there in one molecule of ethanol (CHsOH)?
3
(B) 4
(C) 7
(D) 9
062710-16
The relative molecular mass of ammonium nitrate, NH4NO3, is
(A)
42
(B)
77
(C) 80
(D) 126
062Z10-17
What happens to the atoms of matter when a chemical reaction takes place?
(A) The atoms move faster and further apart.
(B) New atoms are created to form new substances.
(C)Some of the atoms are destroyed to form new molecules
(D)
The atoms rearrange themselves to form
new
molecules.
062Z10-18
Which of the following statements are true of air?
(I)
It contains atoms of gases.
(11) It contains molecules made up of like atoms.
(11) It contains molecules made up of unlike atoms.
(A) Il only
(B)and Il only
(C) II and Il only
(D) 1, Iland
Science Drill Questions
10-7
0
6
2
7
1
0
-
1
9
property
f tthe
of
elements is used to decide their order in the Periodic Table?
What
(A)
Atomic mass
(B)
Valence electrons
(C) Boiling point
(D) Atomic n u m b e r
0 7 2 7 1 0 - 2 0
Which one
of the following has the most number of different
atoms
present?
(A) NaC
(B) H,SO
(C) CH
(D) FeO3
072Z10-21
identifies the
Which of the following correctly
207
A
82
ElectronsS
Protons
A)
207
82
(B)
125
125
(C)
82
125
(D
82
82
in the
number of electrons and protons
following
atom:
10-8
072Z10-22
Which ofthe following diagrams represents a reaction between two elements which
hich isis notuo
not yet
(A)
(B)
C)
(D)
082Z10-23
Which of the
following has the same number of electrons as O?
(A) Ca2
(8) s2
(C) N
(D) K*
08ZZ10-24
What is the chemical formula of the compound
H
(A) CH,02
(B) CH,O
(C) CHO
(D) (CHO)2
e r bril u e s t u
H
given below?
completed?
10-9
082210-25
Which
()
Its atomic number is
(11) Its
(11)
(IV)
lowing statements are true
of the follov
atom is
about
potassium atom?
19
bigger than
an
atom of
bromine
It has 20 neutrons.
It has
a
positive electric charge
(A) Iand I
(B)1, l
and IV
(C)1, Il and
(D) 1,
iII
ill and IV
O8zZ10-26
Which of the following statements is false?
(A) Sulphur is an element because its molecules are made up of single kind of atom only.
(B) Sodium hydroxide is a compound because its molecules are made up of two kinds of atoms, sodium and
hydrogen only.
(C) A molecule of nitrogen gas comprises of nitrogen atoms.
(D) The chemical combination of hydrogen and oxygen atoms gives rise to the formation of water.
082710-27
An atom of element X has a proton number 13 and mass number 27. Which symbol is correct for the ion of X
when it loses 3 electrons?
(A)
27
(B)
3
13
C)
24
1
(D)
24
X
13
062Z10-28
Which of the following chemical formula is
correctr
(A) Mg.CO3
(B) A/OH
(c) K,SO
(D) A/(NO)2
10
atoms, molecules and ions
10-10
062Z10-29
Which of the following pair of elements will combine to form an ionic compound?
(A) carbon and chlorine
(B) oxygen and carbon
(C) hydrogen and oxygen
(D) fluorine and sodium
07ZZ10-30
How many atoms are there in one molecule of the compound HS04?
(A) 3
(8)
S
(C)
7
(D)
072Z10-31
Helium
has two isotopes,
3,
He and
4
He
2
Which statement about an atom of the lighter isotopes of helium is correct?
(A) It contains two neutrons.
(B) It contains three electrons.
(C) It contains a total of three protons and neutrons.
(D) It contains one fewer proton than an atom of the heavier isotope.
07Z10-32
An element X has
proton number 3. Which statement about X is correct?
(A) It is a gas at room temperature and pressure.
(B) It is in Group ll of Periodic Table.
(C) It forms ions by gaining electrons.
(D) It reacts with cold water.
Science Drill Qvestions
10 11
i4h tormla repreSens the
ide
of arn
eernert in
Groo
Derco
()
(0)Y
o104
of the following is the
Whih
correct formula
for
iron
(A) fe,50,
(1)
sulphate?
(6) Fe(50,)
C) FesO
(0) Fe,(S0,)
07221035
Which of the
(A)
llowingi
a
molecule of element?
H
(B) K
(C) CO
(D) NH
072210-36
An atom of Q has atomic number 16 while an atom of Y has atomic number 19. The reaction between Q and Y
is likely to form
(A)
an
ionic compound with the formula Y,Q.
B)
an
ionic compound with the formula YQg.
(C
an
ionic compound with the formula YQ.
(D) an ionic compound with the formula Y,Q2
10
atoms, molecules ande
10-12
Questions
062710-37
DdW
two
separate diagrams to
represent
a
of an element
between molecules
(6) State one similarity and one differen.
CWhy is the smallest particle of
molecules
compound
a
of an
molecule and not
and a compound.
element
olecules of a comp
and mole
an atom?
062Z10-38
Calcium is solid at room temperature.
d
()
rom
the periodic table, find out how
many
electrons,
protons and
neutrons does a
neutral atom of
calcium contains.
A student makes calcium chloride in the
that
laboratory. He knows
calcium chloride was
formed
by ionic
bonding.
formed.
(i)
Describe how ions
()
Looking
at
(i)
chloride is
The chemical formula of calcium
are
calcium would be
the periodic table, deduce if
CaCl2.
an
anion
or cation.
of each element is present in
How many of atom(5)
calcium chloride?
(c) Copy and complete the passage
below.
calcium atom is
At the centre of the
and neutral,
Orbiting around are the
07Zz10-39
listing the
Complete the following table,
Compound
(a)
Ammonia gas
NH
(b)
Lead (1) chloride
PbClh
(C)
Copper () nitrate
Cu(NO3)2
(d)
Ethanol
CH,OH
Science Drill Questions
It contains the positively charged
the.
number and
molecule.
type of atoms present in each
Number and type of atoms
10-13
072210-40
hle below shows the atomic number of the elements in the second period of the Periodic Tabie.
The t a b l e
Element
i
Be
Atomic
6
8
F
Ne
9
10
number
How are
(a)
the elements shOwn above
arranged
in the Periodic Table?
Some of the elements form ions as shown below. Fill in the table to show the formula of the missing ions
b
and the number of electrons and protons present in each ion.
Element
lon
No. of Electrons
No. of protons
Li
Li
i)
(ii)
Be
(ii)
2
(iv)
()
(vi)
10
(vii)
(vii)
F
072710-41
a) What
is
a
chemical formula?
(b) The molecular formula of a compound is CHi20s. This compound can be produced naturally by plants.
(i)
Name this compound.
(i) The atoms which go in to make the compound are
and
9
c) An atom of an element Xmay be written as x
4
(i)
In the symbol what do the numbers 9 and 4 represent?
(i) What is the number of protons, electrons and neutrons in the atom X?
(n) The atom X loses 2 electrons to form an ion. Draw the electronic structure of the ion formed,
showing the nucleus and electron shells and indicate the charge found on the ion.
10
atoms, molecules and ions
10- 14
06ZZ10-42
ElementA, BC, D and E have the following electronic structures.
Element
Electronic structure
A
2,8,1
B
2,8,8,2
C
2,6
D
2,8,8
E
2,1
(a) Which elements are non-metals?
(b) Which two elements are in the same group of the Periodic Table?
06ZZ10-43
Write the chemical formula of the following substances:
(a) Magnesium hydroxide
(b) Copper (1) oxide
(c) Aluminium sulphate
06ZZ10-44
The atom of element X contains eleven protons, twelve neutrons and eleven electrons.
(a) Use the Periodic Table to identify element X.
(b) When atom X loses its electron(s) in the outermost shell, an ion is formed. Write the atomic symbol for
this ion.
Science 0rii Questions
10-15
072Z10-45
The table
below showstthe atomic number of the following elements:
He
Li
Be
B
1
2
3
4
5
Na
Mg
Al
Si
P
12
13
14
15
H
11
Ceam
Periodic Table
the extract of the
largest
(a) has the
(b)
number
Ne
N
8
9
10
CI
Ar
K
Ca
17
18
19
20
6
16
shown,
name
the element which
of protons.
number of protons.
has the fewest
c)will lose two
electrons
easily.
two electrons easily.
(d) will gain
072710-46
Predict the
charge
on
Hence deduce if the
each of the
particle is
an
following particles.
atom,
a
negative ion
or a
positive ion?
Key: proton, neutron O, electron
(c)
(b)
a
O
S
Charge
Charge:
Charge:
ype of particle:
10
atoms, molecules and ions
10-16
07Z710-47
information in the table below to
Use the
answer
Oxygen
Carbon (Diamond)
Element
the following questions.
Sodium
Silicon
Chlorine
Na
Si
CI
Symbol
C
Proton number
6
8
11
14
17
Mass number
12
16
23
28
35.5
be written
as
(a) The electronic
structure
of the carbon atom
can
(2,4).
Write down the
electronic h
trutare
(i) Oxygen
ii) Silicon
(6) What is the number of neutrons present in
)
Sodium?
(i)
Silicon?
one
atom of
(c) Which element conducts electricity?
08ZZ10-48
Atoms of
beryllium and magnesium
24
Be
(a)
12
What do the
are
represented respectively, by the symbols:
MB
these atoms?
following numbers tell you about
(in the symbol for beryllium)
(i)
4
(i)
24
(in
the
symbol for magnesium)
(b)
Draw the electronic structures of
beryllium and magnesium, showing only the
(c)
How do the electronic structures
of beryllium and magnesium
the Periodic Table?
Science Drill Questions
indicate
they
outermost electrons.
are
both in the same greu
10-17
O72Z10-49
The
raoh below plots the nucleon numbers of different elements against their proton numbers.
25
Na
Ne
20
0
15
Be
10
5
He
0
2
4
6
8
10
12
Proton number
(a) What is meant by
)
Proton number?
(i) Nucleon number?
6) Classify the elements into those with
0)
More protons than neutrons.
(i) More neutrons than protons (give at least three).
() The same number of neutrons and protons (give at least three).
rom the graph, predict the nucleon number of an atom with a proton number of 12.
d)sotopes are
atoms with same number of protons from the same element. Boron (B) has two isotopes,
0oron-10 and boron-11. Write the chemical symbols for these isotopes. Include the proton numbers and
nucleon numbers.
10
atoms, molecules and ions
10-18
08ZZ10-550
Study the table shown below.
Atom/lon
Electrons
Protons
Mass number
P
12
12
24
Q
10
8
16
R
18
16
32
10
10
20
10
13
27
(a) Which two are atoms? Explain your answer.
(b) Name a positive ion from the table. Explain how you derive your answer.
(c)
The number of protons and neutrons in an atom is always equal. Is the above statement correct? Expiain
your answer by using the information provided in the table above.
087710-51
Study the following models and describe what they represent.
CO
(b)
(a)
3
(c)
(d)
062Z10-52
Complete the table of chemical formulas shown below.
Name
Group
Sulphate
Hydroxide
Chloride
(a)
Calcium
CaSO
()
(i)
(b)
Gallium
(i)
Ga(OH)
(i)
Science Drill Questions
10-19
D6Z10-53
These diagrams show the electron arrangement in the outer shells of five elements, A to E. All the
element are from Perioc 3 of the Periodic Table.
-
B
ldentify which
(a)
elements
are
metals and which
is most likely to be in
(b) Which element
c)Which element will form
d)Which element has a
an
ion
of the type X**?
two elements will form an ionic
() Which
element will form
Two isotopes of uranium is
non-metals.
Group VI?
e) Which
an
are
number of 15?
proton
06ZZ10-54
D
C
compound with
ion of the type
a
formula of the type YZ2?
P?
in this statement.
238 U and
and 235
U. Explain the meaning of isotopes
92
92
067210-55
configuration.
Explain with the aid of electronic
31
4
Why elements N
7
a
0)
Why aluminum
h e difference
and
and
P
are
in the
same
group?
15
sulphur are in the
between a potassium
same
period?
atom and potassium
ion.
10
atoms, molecules and ions
10-20
062Z10-56
The
diagram shows
a
molecule with
one
atom labelled.
H
H
Unlabelled atom
(a) ldentify the
unlabelled atom and
give a
reason
to
support your
answer.
(b) Give the chemical formula of the molecule.
07ZZ10-57
D, E, F and G are four consecutive elements with proton number n, n+1, n+2, n+3 respectively. F is
chemically inert gas in period 2. Using dot and cross diagram, draw the bonding formed between
elements E and G.
07ZZ10-58
(a) State the number of each type of atoms present in the following molecules.
(6)
CH,cooH
(ii) Br2
(b) Work out the formula of each of the following substances from the composition of the molecules.
)
One calcium atom, two chlorine atoms
(i) One magnesium atom, one sulphur atom, four oxygen atoms