Periodicity

Question 1

How are the element arranged in the periodic table?

Answer 1

They are arranged in the order of increasing atomic numbers.

Question 2

What is meant by periodicity?

Answer 2

The repeating trends in chemical and physical properties

Question 3

Define first ionisation energy.

Answer 3

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 4

Write an equation for the first ionisation energy of magnesium.

Answer 4

Mg (g) —> Mg+ (g) + e-

Question 5

What are the factors that affect ionisation energy?

Answer 5

• atomic radius
• nuclear charge
• electron shielding or screening

Question 6

Why does the first ionisation energy decrease between group 2 and 3?

Answer 6

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 7

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

Answer 7

The decrease between 5 and 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 8

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

Answer 8

Decrease
- there is aincrease in atomic radius
- increase in electron shielding

Question 9

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

Answer 9

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 10

What are the properties of giant metallic lattices? (4)

Answer 10

• high mp and bp
• good conductors of electricity
• malleable
• ductile

Question 11

What is a ductile metal?

Answer 11

The metal can be made to stretch.

Question 12

What is a malleable metal?

Answer 12

The metal can be shaped into different forms.

Question 13

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

Answer 13

• 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 14

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

Answer 14

• Na, Mg, Al —> giant metallic; strong attraction between positive ions and delocalised electrons 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