Periodicity

What 3 factors affect first ionisation energy?

charge, atomic radius, shielding

What is meant by periodicity?

repeating trends in properties of elements across a period

Write the equation for the first ionisation energy for oxygen

O(g) = O+(g) + e-

Define first ionisation energy

energy needed to remove 1 mole electrons from 1 mole of gaseous atoms to produce 1 mole gaseous ions

How does the first ionisation energy change across a period?

increases

How does the first ionisation energy change down a group?

decreases

Why does the first ionisation energy increase across a period?

charge increases, radius decreases (increased attraction), therefore more energy needed (shielding same)

Why does the first ionisation energy decrease down a group?

atomic radius increases, shielding increases therefore attraction decreases (charge stays same)

State and explain the trend in first ionisation energies shown by the elements with the atomic numbers 2, 10 and 18

decreasing ionisation, increased nuclear charge, outer electron experiences greater attractive force but shielding & radius increase so overcome

Explain why the second ionisation energy of oxygen has a greater value than the first ionisation energy of oxygen

Same charge to less electrons so attraction to remaining electrons is greater

Explain why the first ionisation energy of B is less than Be

B has extra electron in p-shell, requiring less energy to remove as higher energy (lower attraction to nucleas)

Explain why the ionisation energy of oxygen is lower than nitrogen, even though it is further along the period

oxygen has 2 paired electrons in 2p subshell, paired electrons repel more so is easier to remove them

What is the difference between the bonding in a simple molecular lattice and a giant covalent lattice?

simple molecular has london forces between molecules, giant covalent has covalent bonds between atoms