Module 3 - Periodicity

Question 1

How are the elements
arranged in a periodic table?

Answer 1

They are arranged in the order of
increasing atomic numbers

Question 2

What is a period on a periodic
table?

Answer 2

The horizontal rows in the periodic table

Question 3

What is a group on a periodic
table?

Answer 3

The vertical columns

Question 4

What is meant by periodicity?

Answer 4

The repeating trends in chemical and
physical properties

Question 5

What change happens across
each period?

Answer 5

Elements change from metals to non
metals

Question 6

How can the electron
configuration be written in
short?

Answer 6

The noble gas before the element is
used to abbreviate
E.g Li → 1s2 2s1 ; Li → [He] 2s1

Question 7

Define first ionisation energy

Answer 7

The energy required to remove one
electron from each atom in one mole of
the gaseous element to form one mole of
gaseous 1+ ions

Question 8

Write an equation for the first
ionisation energy of
magnesium

Answer 8

Mg (g) → Mg+ (g) + e-

Question 9

What are the factors that affect
ionisation energy?

Answer 9

● Atomic radius
● Nuclear charge
● Electron shielding or screening

Question 10

Explain the trend of period 3

Answer 10

First Ionisation energy increases across period 3 because of:
-Increased nuclear charge
-Decreased atomic radius
-Same electron shielding
which means more energy is needed to remove the first electron.
Dips at Al because: outer electron is in a 3p orbital, higher energy than 3s orbital → less
energy needed to remove electron
Dips at S because one 3p orbital contains two electrons → repulsion between paired
electrons → less energy needed to remove one

Question 11

Why does first ionisation
energy decrease between
group 2 to 3?

Answer 11

● Decrease between 2 to 3 because in group 3
the outermost electrons are in p orbitals
whereas in group 2 they are in s orbital, so the
electrons are easier to be removed

Question 12

Why does first ionisation
energy decrease between
group 5 to 6?

Answer 12

The decrease between 5 to 6 is due to the group
5 electrons in p orbital are single electrons and in
group 6 the outermost electrons are spin paired,
with some repulsion. Therefore the electrons are
slightly easier to remove

Question 13

Does first ionisation increase
or decrease between the end
of one period and the start of
next? Why?

Answer 13

Decrease
● There is increase in atomic radius
● Increase in electron shielding

Question 14

Does first ionisation increase
or decrease down a group?
Why?

Answer 14

● Decrease
● Shielding increases → weaker attraction
● Atomic radius increases → distance between the outer
electrons and nucleus increases → weaker attraction
● Increase in number of protons is outweighed by increase
in distance and shielding

Question 15

What are the properties of
giant metallic lattices?

4 points

Answer 15

● High melting and boiling point
● Good electrical conductors
● Malleability
● Ductility

Question 16

What is a ductile metal?

Answer 16

The metal can be made stretched. E.g
Can be made into wires

Question 17

What is a malleable metal?

Answer 17

The metal can be shaped into different
forms

Question 18

Describe the structure, forces
and bonding in every element
across period 2

Answer 18

● Li & Be → giant metallic ; strong attraction between
positive ions and delocalised electrons ; metallic bonding
● B & C → giant covalent ; strong forces between atoms ;
covalent
● N2, O2, F2, Ne → simple molecular ; weak intermolecular
forces between molecules ; covalent bonding within
molecules and intermolecular forces between molecules

Question 19

Describe the structure, forces
and bonding in every element
across period 3

Answer 19

● Na, Mg, Al → giant metallic ; strong attraction between
positive ions and delocalised electrons ; metallic bonding
● Si → giant covalent ; strong forces between atoms ;
covalent
● P4 , S8 , Cl2 , Ar → simple molecular ; weak intermolecular
forces between molecules ; covalent bonding within
molecules and intermolecular forces between molecules