Periodicity Flashcards
Explain the trend of ionisation energy down a group
It increases down a group
As elements down a group have more electron shells
So have a larger atomic radius
Therefore the outer electrons are further away from the nucleus
This greatly reduces nuclear attraction to the nucleus
Moreover the extra inner shells shield the outer electrons from nuclear attraction
Explain the trend of ionisation energy across a period
It increases across a period
This is because the no. of protons increase
The positive charge of the element increases
So the electrons are pulled closer to the nucleus
The atomic radius decreases
Explain the group 3 exception to ionisation energy across a period
The outer electron is in a p orbital not s.
The P orbital has slightly higher energy then s
Also it has additional shielding by the s electron
This overrides the effect of the increased nuclear charge resulting in the IE decreasing a bit
(shows evidence for sub-shells)
Explain the group 6 exception to ionisation energy across a period
In group 6 elements the electron is removed from a paired orbital
So revulsion between the electron in an orbital means electrons are easier to remove from paired orbitals
Explain the trend in boiling point for metals across a period
It increases
Because metallic bonds increase in strength as the atomic radius decreases
And the number of delocalised electrons increase
Explain the trend in reactivity down group 2
It increases
As the IE decreases
Due to increasing atomic radius and shielding effect
Explain halogens reactivity
They get less reactive down the group
As the atomic radii increase
Outer electrons are further away from nucleus
The outer electron are also shielded from the attraction of the nucleus because there are more inner electrons
This makes it harder for larger atoms to attract the electrons needed to form an ion so larger atoms are less reactive
Explain the trend of ionisation energy across a period
It increases across a period
This is because the no. of protons increase
The positive charge of the element increases
So the electrons are pulled closer to the nucleus
The atomic radius decreases
Explain the group 3 exception to ionisation energy across a period
The outer electron is in a p orbital not s.
The P orbital has slightly higher energy then s
Also it has additional shielding by the s electron
This overrides the effect of the increased nuclear charge resulting in the IE decreasing a bit
(shows evidence for sub-shells)
Explain the group 6 exception to ionisation energy across a period
In group 6 elements the electron is removed from a paired orbital
So revulsion between the electron in an orbital means electrons are easier to remove from paired orbitals
Explain the trend in boiling point for metals across a period
It increases
Because metallic bonds increase in strength as the atomic radius decreases
And the number of delocalised electrons increase
Explain the trend in reactivity down group 2
It increases
As the IE decreases
Due to increasing atomic radius and shielding effect
Explain halogens reactivity
They get less reactive down the group
As the atomic radii increase
Outer electrons are further away from nucleus
The outer electron are also shielded from the attraction of the nucleus because there are more inner electrons
This makes it harder for larger atoms to attract the electrons needed to form an ion so larger atoms are less reactive
