7.2 Flashcards
What is periodicity?
Repeating pattern across different periods
What is the first ionisation energy?
Energy needed to remove a mole of electrons from one mole of gaseous atoms
Write an equation for the first ionisation energy?
H(g) —-> H+ (g) + e-
What are the 3 factors that affect ionisation energy?
Attraction of the nucleus, atomic radius and electron sheilding
How does nuclear charge affect ionisation energy?
Greater nuclear charge means there are more protons in the nucleus, which also means that there is greater electrostatic attraction for outer electrons. As a result, first ionisation energy is higher.
How does atomic radius affect ionisation energy?
Greater atomic radius there is less electrostatic attraction and therefore lower ionisation energy.
How does electron sheilding affect ionisation energy?
Inner electrons repel outer shell electrons- this repulsion is called the sheilding effect and reduces attraction between nucleus and outer electrons.
What is the second ionisation energy for oxygen?
O + (g) —-> O2+ (g) + e-
What is the trend down the group?
Down a group nuclear charge increases, however this is outweighed by the increasing atomic radius/sheilding which means there is reduced electrostatic attraction between the nucleus and outermost electrons
What is the trend across a period?
Ionisation energy increases, nuclear charge increases, shielding is the same and atomic radius decreases.
Why is there a drop in ionisation energy between groups 2 and 3?
The outer electron in group 3 elements is in a p orbital rather than an s orbital. The p orbital has slightly higher energy than an s orbital in the same shell so the electron on average is said to be further from nucleus. The p orbital also has additional sheilding provided from s electrons which override the effect of nuclear charge, resulting in ionisation energy drop.
What is the drop between group 5 and 6?
Due to p orbital repulsion. In group 5 elements, the electron is being removed from an orbital containing 1 electron. In group 6 elements, the electrons being removed from an orbital containing 2 electrons. The repulsion between 2 electrons in an orbital means that the electrons are easier to remove from shared orbitals.
What do successive ionisation energy allows us to make predictions about?
- number of electrons in the outer shell
- the group of the element in the element
- the identity
What is the drop between group 2 and 3?
- the outer electron is a p orbital rather than an s orbital- p orbital has slightly higher energy level than s orbital so is further from the nucleus therefore there is greater shielding and the ionisation energy is lower
Why is there a drop between group 5 and 6?
5 electrons in p orbital are single electrons while in group 6 they are spin paired making it easier to remove
