C7 - Periodicity

Question 1

Define first ionisation energy

Answer 1

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous positive ions

Question 2

What are the 3 factors that affect first ionisation energy?

Answer 2

proton number
distance from nucleus (atomic radius)
shielding

Question 3

Explain the trend in the reactivity of group 1

Answer 3

• decreases down a group
• despite increased nuclear charge
• due to increased shielding and greater distance from the nucleus
• outer electron is held less strongly and easier to remove

Question 4

Explain the trends across a period

Answer 4

• protons increase
• shielding = same
• distance from nucleus = smaller
• electrons are held more strongly and therefore harder to remove

Question 5

Define metallic bonding

Answer 5

The electrostatic attraction between metal ions and delocalised electrons

Question 6

In general, are metals soluble or insoluble

Answer 6

Insoluble, metallic bonding is strong therefore weak intermolecular forces with water will not affect the structure

Question 7

State and describe the melting points for giant covalent structures

Answer 7

Extremely high

Covalent bonds have to be broken - very very strong

Question 8

Describe what the trend for melting point across period 2 looks like

Answer 8

Increases through Li and Be (metallic bonding gets stronger)
B and C increases (giant covalent structure with more bonds)
N, O, F, Ne (very low, very slight increase- weak London forces between molecules)

Question 9

The first ionisation energy generally increases between Li and Ne however there are 2 dips in the graph, explain where these are and why

Answer 9

Be – B
Introduction of p subshell means s orbitals are causing more shielding

N – O
electrons now pairing up to fill p orbitals causing some repulsion so are slightly easier to remove