Periodicity

Question 1

What is the periodic table arranged by?

Answer 1

Increasing atomic number

Question 2

Periodicity

Answer 2

A repeating pattern (chemical or physical) across different periods

Question 3

What happens along the period?

Answer 3

Nuclear charge increases/Atomic number increases
Shielding remains the same
Atomic radius decreases

Question 4

Ionisation

Answer 4

When atoms gain or lose electrons to form positive and negative ions respectively

Question 5

First Ionisation Energy

Answer 5

Energy required to remove one mole of electrons

From one mole of gaseous atoms of an element

To form one mole of gaseous 1+ ions

Question 6

Why are ionisation energies endothermic reactions?

Answer 6

negative electrons are held in their electron shells (by
their attraction with the positively charged nucleus)

MORE energy must be SUPPLIED than is released in order overcome this attraction and therefore remove one electron
from a gaseous atom

Question 7

Successive ionisation energies

Answer 7

The amount of
energy required to remove each electron in turn.

Question 8

Second Ionisation Energy

Answer 8

the energy required to remove one mole of electrons

From one mole of gaseous X+ ions

To form one mole of gaseous X 2+ ions

Question 9

Equation for the first ionisation energy of chlorine

Answer 9

Cl (g) 🡪 Cl+ (g) + e-

Question 10

Equation for the fourth ionisation energy of chlorine

Answer 10

Cl3+ (g) 🡪 Cl4+ (g) + e-

Question 11

How to differentiate an element’s group from a graph of successive ionisation energies

Answer 11

The point where there is the greatest difference in ionisation energies

Question 12

Factors affecting ionisation energies

Answer 12

Atomic Radius

Nuclear Charge

Electron Shielding

Question 13

How does ATOMIC RADIUS affect ionisation energy?

Answer 13

LARGE atomic radius = SMALL ELECTROSTATIC ATTRACTION between nucleus and outermost electron

Positivley charged NUCLEUS is FURTHER AWAY from outermost ELECTRONS

LOW IE because LESS ENERGY is REQUIRED to REMOVE OUTERMOST ELECTRON

Question 14

How does NUCLEAR CHARGE affect ionisation energy?

Answer 14

HIGH Nuclear charge = LARGER ELECTROSTATIC ATTRACTION between nucleus and outermost electrons

HIGH IE because MORE ENERGY REQUIRED to REMOVE OUTERMOST ELECTRON

Question 15

How does ELECTRON SHIELDING/SHIELDING EFFECT affect ionisation energy?

Answer 15

MORE electron shielding = REDUCED ATTRACTION/ MORE REPULSION between inner and outer electrons

LARGER the ATOM = more electron shells and GREATER ELECTRON SHIELDING

LOW IE because LESS ENERGY is REQUIRED

Question 16

What happens to the ‘factors’ as you go down the group?

Answer 16

Atomic radius increases (IE decreases)

Electron shielding increases (IE decreases)

Nuclear charge increases (IE increases)

Question 17

What is the trend in first ionisation energies across a period?

Answer 17

Nuclear charge increases (the number of proton increases) (IE increases)

Electron shielding stays the same (The number of electron shells stays the
same )

Atomic radius decreases (IE increases)

outer shell electrons experience an increase in nuclear attraction overall across a period

Overall INCREASE in IE

Question 18

Why does Boron have a lower IE than Beryllium?

Answer 18

SHIELDING EFFECT

The outer electron is removed from a 2p sub-shell which is higher in energy than a 2s sub-shell.

The s electrons provide a slightly greater shielding of the p electron.

Therefore, the 2p electron is easier to remove than a 2s electron.

Question 19

Why does Oxygen have a lower IE than Nitrogen? (Try to draw out the electronic configuration of both)

Answer 19

ELECTRON PAIR REPULSION

Nitrogen has a half-filled set of p orbitals.

In oxygen the paired 2p electrons repel one another

This repulsion makes it easier to remove an electron from oxygen compared to nitrogen.

Question 20

Why do simple molecular structures have LOW MP?

Answer 20

Weak London forces exist between their molecules/atoms.

As a result, very little heat energy is needed to break these forces and therefore melt them

Question 21

Why do giant covalent structures have HIGH MP?

Answer 21

Giant covalent lattices contain many strong
covalent bonds

A large amount of heat energy is needed to break these strong covalent bonds

Question 21

Why do giant covalent structures have HIGH MP?