Ionisation energies UNIT 1

Question 0

What factors affect ionisation energies

Answer 0

Nuclear charge
Distance from nucleus
Shielding

Question 1

What is the first ionisation energy

Answer 1

The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

Question 2

How does nuclear charge affect ionisation energies

Answer 2

The more protons, the more positively charged the nucleus is and the stronger the attraction for the electrons

Question 3

How does the distance from the nucleus affect the ionisation energy

Answer 3

Attraction drops with distance. An electron much closer to the nucleus will be much more strongly attracted than one further away

Question 4

How does shielding affect ionisation energy

Answer 4

As number of electrons between outer electrons and nucleus increases the outer electrons feel less attraction towards the nuclear charge

Question 5

What is a high Ionisation energy

Answer 5

It means a high attraction between the electron and the nucleus

Question 6

The lower the ionisation energy the ……… it is to form an ion

Answer 6

EASIER

Question 7

Why does ionisation energy decrease down group 2

Answer 7

If each element down group 2 has an extra electron compared to the one above, the extra inner shells will shield the outer electrons from the attraction of the nucleus. Also the extra shell means the outer electrons are further away from the nucleus, so nucleus attraction greatly reduced.

Question 8

Why does ionisation energy increase across a period

Answer 8

Number of protons increasing making the nucleus very positive which means it will attract the negative electrons strongly, meaning a strong nuclear attraction. Electrons entering same energy level so no increase in shielding, atomic radius is also decreasing, again pulling electrons in closer to nucleus

Question 9

A drop in ionisation energies between group 2 and 3 shows evidence for what?

Answer 9

Sub shell structure

Example, Mg and Al
Al has an outer electron in a 3p orbital rather than 3s. The 3p orbital has a slightly higher energy than the 3s orbital, so the electron is found further from the nucleus. The 3p orbital has additional shielding provided by the 3s2 electrons. Both of these factors override the effect of the increased nuclear charge, so IE drops slightly.

Question 10

The drop in IE between groups 5 and 6 is due to……….

Answer 10

REPULSION

Example with P and S

The shielding is identical in both atoms and the electron is being removed from an identical orbital. In P the electron is being removed from a singly-occupied orbital, but in S the electron is being removed from an orbital containing 2 electrons. The repulsion between the 2 electrons in an orbital means the electrons are easier to remove from shared orbitals, so more evidence for electronic structure model