A3 - Group 2 Flashcards
How many valance electrons in atoms in group 2?
2
What happens to group 2 elements when they react?
They are oxidised because they lose electrons, therefore they can also be called reducing agents.
Give 3 physical properties of group 2 elements:
- Form colourless/white compounds
- Good conductors of electricity
- High melting point
What is the trend in atomic radius in group 2?
As you go down group 2:
- Atomic radius increases
- More electron shells
- So outer electrons are further from the nucleus
What is the trend in melting points in group 2?
As you go down group 2:
- Melting point decreases
- Because ionic radius increases
- So charge density is decreased and there are weaker attractions between ions and delocalised electrons
What is the trend in first ionisation energy in group 2?
As you go down group 2:
- Atomic radius increases
- The attraction between the nucleus and the outer electrons decreases
- So first ionisation energy decreases
What is the oxidation state of group 2 metals as elements?
0
What is the oxidation state of group 2 metals in compounds?
+2
What is the observation when Mg reacts with water?
It reacts vigorously with steam, or produces few bubbled with cold water.
What is the observation when Ca reacts with water?
It reacts quickly with cold water forming bubbled and a cloudy solution.
What is the observation when Sr reacts with water?
It reacts very vigorously.
What is the observation when Ba reacts with water?
It reacts very vigorously.
What is the general word equation for the reaction of a group 2 metal with oxygen?
Metal + oxygen -> metal oxide
What is the general word equation for the reaction of a group 2 metal with water?
Metal + water -> Metal hydroxide + hydrogen
What is the trend when group 2 metals react with acids?
As you go down the group, the reactions get more vigorous.
- The activation energy for the reduction of metal decreases, so reactions occur more readily
- Group 2 elements are oxidised more easily and are therefore better reducing agents
What is the atomisation energy of a metal?
The energy needed to break the bonds holding the atoms together in the metallic lattice.
Why does atomisation energy decrease down group 2?
The electron density decreases as the group goes down, ionic radius increases, attraction between ions and electrons decreases.
Why is second ionisation energy larger than the 1st ionisation energy for the same element?
Shielding stays the same, the proton to electron ratio decreases, so there is a stronger nuclear attraction.
Explain the trend in reactivity down group 2:
- Reactivity increases down the group
- Larger atomic radius
- Increased nuclear charge
- Reacting increases
- Less nuclear attraction
What is the solubility of group II oxides?
They dissolve in water to form hydroxides, but the solubility depends on the solubility of the hydroxide.
What is the solubility of group II hydroxides?
They become more soluble down the group.
What is the solubility of group II sulphates?
They become less soluble down the group.
What are the uses of magnesium and its compounds?
Magnesium hydroxide is used to treat excess stomach acid (in the form of antacid tablets) and in toothpaste to help neutralise mouth acids, which cause tooth decay.
What are the uses of calcium and its compounds?
Calcium carbonate can also be used as an antacid to treat excess stomach acid.
Calcium compounds (both calcium hydroxide and carbonate) can be added to acidic soils to decrease the pH in a process known as liming. This is necessary because the uptake of both macro and micronutrients by crops is pH-dependent.
Calcium hydroxide is used to make lime water.
What are the uses of barium compounds?
Barium sulfate forms ppt in a test for sulfate ions.
‘Barium meal’ for x-rays of the stomach and digestive system - barium atoms are very good at absorbing x-rays, and have poor solubility which allows this to occur safely.
