3.1.1 - Periodictiy Flashcards
Define periodicity.
Periodicity is the repeating pattern of properties in a group
What are the 4 blocks that the periodic table is split into?
- S block
- P block
- D block
- F block
What is the trend in electron configuration?
You add 1 electron as you go across the period, when you start a new period you fill a new shell.
Why do elements with similar electron configurations react similarly?
Chemical reactions only involve outer shell electrons so they have similar chemical reactions.
How are elements classified?
Elements that have the same number of outer shell electrons are put in the same group.
What is ionisation energy?
Ionisation energy is the energy required to form a positive ion. It is a measure of how easily an atom loses an electron.
Define first ionisation energy?
The energy required to remove one electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous +1 ions.
What is the general equation for first ionisation energy?
X —> X+ + e-
What are the 3 main factors effecting ionisation energy?
- atomic radius
- nuclear charge
- electron shielding
What effect does the atomic radius have on an atom?
The greater the distance the lead nuclear attraction, forces of attraction stop sharply with the increasing distance.
What effect does nuclear charge have on an atom?
As the nuclear charge increases there is a greater attraction between the nucleus and the outer shell electrons.
What effect does electron shielding have on an atom?
The inner electrons repel the outer shell electrons, this repulsion is called shielding. The more shells there are the more shielding there is so there is less nuclear attraction.
What happens to the atomic radius, nuclear charge and electron shielding as you go down the group?
All three increase as you go down the group.
What happens to the atomic radius, nuclear charge and electron shielding as you go across the period?
- the nuclear charge increases
- the atomic radius
- the electron shielding
What is the trend in ionisation energy as you go down the group?
The nuclear attraction decreases as you go down so the ionisation energy increases as you go down.
What is the trend in ionisation energy going across the periodic table?
The nuclear attraction increases so the ionisation energy increases across each period.
What happens to the ionisation energy between group 2 and 3?
The ionisation energy decreases.
Why does the ionisation energy between group 2 and 3 decrease?
It is due to the sub shell structure:
- the outer electrons in group 3 are in the p-orbital and the p-orbitals have more energy that’s the s-orbitals
- so the electrons are further away from the nucleus
- p-orbitals also have additional shielding provided by the s-orbitals
- the increased shielding and atomic radius override the affects of the increase in nuclear charge so the ionisation energy drops
What is successive ionisation energy?
It is a measure of the energy required to remove each electron in turn.