EL 8 Flashcards
Explain why FIE increases as you go down a group
- adding a shell of electrons each time (bigger radius)
- greater electron shielding
- greater shielding and radius negates effect of larger nucleus
Lesss energy required to remove outer electrons - decreasing the FIE
Explain why FIE increases as you go along a period
- Increased number of protons
- Same number of shells
- Stronger attraction between the nucleus and outer electrons
- Therefore more energy is required to remove the outer electrons
- INCREASING FIE
What is ionisation?
The removal of one or more electrons
What is ionisation enthalpy?
The energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
First ionisation of oxygen equation
O -> O+ + e-
The lower the ionisation enthalpy ____
The easier it is to remove an outer electron and form an ion
What 3 things affect the size of ionisation enthalpies?
- Atomic radius
- Nuclear charge
- Electron shielding
Why does an atom with a low atomic radius have a low ionisation enthalpy?
The further the outer shell electrons are from the positive nucleus, the leads they’ll be attracted towards the nucleus
Why does an atom with a high nuclear charge have a high ionisation enthalpy?
The more protons in the nucleus, the more it’ll attract the outer electrons
So it’ll be harder to remove the electrons
Why does an atom with a high electron shielding have a low ionisation enthalpy?
More inner electrons means more shielding
And this means the attractive force between the electrons and positive nucleus will be more intercepted
Why does first ionisation enthalpy decrease as you go down group 1 and 2?
1) as you go down the group, the outer electrons are in shells further from the nucleus
SO they are attracted to the nucleus less
2) the amount of shielding also increases because there are more filled inner shells
SO greater interception
SO less attraction for the outer shell electrons
Why does ionization enthalpy increase as you go across a period?
Because the number of protons is increasing
So outer electrons are attracted more strongly to the nucleus
Why do S-block metals have low ionisation enthalpies?
- They have low nuclear charges
- so the outer electron is less attracted to the nucleus and easier to lose
Why do P-block metals have higher ionisation enthalpies?
- They have more protons so higher nuclear charges
- So greater attraction between the nucleus and the outer electron
Group 2 element + water -> ?
Metal hydroxide + hydrogen
Group 2 element + oxygen -> ?
oxides (solid white precipitate)
What happens to reactivity as you go down group 2?
Increases
What type of elements are group 2 hydroxides and oxides?
Bases
Why do group 2 hydroxides form alkaline solutions in water?
The metal hydroxides dissolve and the hydroxide ions make these solutions strongly alkaline
Group 2 oxide OR hydroxide + acid ->
Salt + water
What is thermal decomposition?
When a substance breaks down when heated
What do group 2 carbonates decompose to form?
Metal oxide + CO2
What happens to thermal stability of carbonates as you move down group?
It increases
What doe sit mean if a substance is more thermally stable?
It takes more heat to break it down
Why would a carbonate ion be less stable?
- the cation is further down group 2 so larger so has lower charge density
- so distortion is smaller as the cation polarises it less
- so it is more stable
What happens to metallicness as you go down a group?
Increases
What happens as elements get more metallic?
They get more reactive
What happens to metallicness across a period?
Decreases
3 group 2 properties
Reasonably high MP & BP
Low densities
From colourless compounds
What is 1st ionisation enthalpy?
A measure of how easily an atom loses an electron to form an ion
What are successive ionization enthalpies?
Enthalpies after the first ionization enthalpy
Why is each successive IE larger than the one before?
The distance of each electron from the nucleus decrease slightly so the nuclear attraction increases
What happens to groups 2 elements in redox reactions?
- They are oxidized
- When they are used as strong reducing agents
Group 2 + water ->
Hydroxides + hydrogen
What is charge density?
A measure of the concentration of charge on the cation
Base sate symbol
S
Alkali state symbol
Aq
What happens to solubility of carbonates as you go down group 2?
Less soluble
What happens to solubility of hydroxide as you go down group 2 and why?
Increases
As size of metal ion increases
So less attraction between metal cation and OH- anion in the hydroxide
Which makes it easier for water molecules to break up the lattice
What are 2 uses of group 2 hydroxides?
Calcium hydroxide is used by farmers and gardeners as “lime” to neutralize acidic soil
Magnesium hydroxide is used in “milk of magnesia” to relieve indigestion by neutralizing stomach acidic
