3.1.1: 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

Why does first ionisation energy increases across period 3?

Answer 10

-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 marks)

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 mean?

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