Groups 1, 2 & 7 Flashcards
What are the trends in 1st ionisation energy as you go down groups 1 + 2?
As you go down group 1 +2, ionisation energy decreases as the distance between the nucleus + valence electrons increases, so outer electrons are easier to remove.
The nuclear charge also increases, however the shielding from other shells outweighs this.
Describe reactivity trends down groups 1 + 2
Reactivity down the groups increase as they react by losing electrons
Explain HISDOG
Hydroxides Increase Sulphates Decrease dOwn Group
Trends in solubility down group 2
Explain the trend in thermal decomposition down groups 1 + 2
Thermal decomposition gets harder down the groups, as the cations get larger and are less polarising, so there is less weakening of bonds within the anion
Show what happens with Li and group 2 nitrates
2LiNO3(s) —> Li2O(s) + 2NO2(g) + 1/2 O2(g)
NO2 = brown fumes
(Group 2 reacts in same way)
Show what happens with the rest of group 1 nitrates
NaNO3(s) —> NaNO2(s) + 1/2 O2(g)
No brown fumes
Show what happens with Li and group 2 carbonates
LiCO3(s) —> Li2O(s) + CO2(g)
CO2 turns limewater milky
(Group 2 reacts in same way)
Explain what happens to rest of group 1 carbonates
Do not undergo thermal decomposition as cations are too large and too lowly charged, so cannot polarise anion enough to break bonds
Describe a flame test
Clean nichrome wire by dipping in HCl
Put wire in flame
Dip wire in metal sample
Put in blue flame and observe colour
What colour does Li show?
Red
What colour does Na show?
Yellow/orange
What colour does K show?
Lilac
What colour does Rb show?
Red/purple
What colour does Cs show?
Blue/violet
What colours do Be and Mg show?
No visible colours emitted (out of visible light spectrum)
What colour does Ca show?
Brick red
What colour does Sr show?
Crimson red
What colour does Ba show?
Apple green
How do we observe the colours in flame tests?
Electrons absorb energy and are excited from ground state energy level to higher (excited) state.
When they fall back down again energy of a specific frequency is released which we observe as colour
Describe trend in melting point of group 7
Melting point increases down the group because there are more electrons, so are more/stronger London forces between the molecules, therefore more energy is required to break them and change physical state
Explain trend in electronegativity down group 7
Decreases down group as:
Nuclear charge increases but shielding also increases and outweighs nuclear charge. Atomic radius also increases so nuclear attraction on bonded electrons decreases
Explain trend in reactivity down group 7
Decreases down group as:
Nuclear charge increases but shielding also increases and outweighs nuclear charge. Atomic radius also increases so nuclear attraction on incoming electrons decreases
State the colours of chlorine as an element, in aqueous and organic solutions
Element: green gas
Aqueous: pale green
Organic: pale green
State the colours of bromine as an element and in aqueous and organic solutions
Element: red/brown liquid
Aqueous: orange
Organic: orange
