Group 1

GCSE Group 1

General Properties

• S block elements
• Lose an electron to produce a uni-positive ion
• They are reducing agents
• Ionisation energy decreases down the group
• Reactivity increases down the group
• Lithium shows a diagonal relationship with Magnesium

Physical Properties

• They are soft metals with a low density
• Melting points decreases drastically down the group
• Good conductors of heat and electricity
• Stored under oil since they are highly reactive with air.

Chemical Properties

With O₂

4Li + O₂ → 2Li₂O

Ithium only produces the normal oxide while Potassium can produce the superoxide and the peroxide as well. The tendency of the alkali metals to produce the peroxide and the superoxide increases down the group.

4K + O₂ → 2K₂O

K + O₂ → KO₂

2K + O₂ → K₂O₂

With H₂O

2Li_(s) + 2H₂O_(l) → 2LiOH_(aq) + H_2(g)

2Na_(s) + 2H₂O_(l) → 2NaOH_(aq) + H_2(g)

2K_(s) + 2H₂O_(l) → 2KOH_(aq) + H_2(g)

The alkali metals react vigorously with water, with the reactivity increasing down the group. Lithium will actually float on water gradually disappearing as time passes by, sodium will start fizzing around on the surface of the water with potassium reacting vigorously.

Hydroxides

All group 1 hydroxides are soluble to produce an alkali solution

The solid hydroxides are deliquescent; they absorb water until they dissolve

All group 1 hydroxides are thermally stable except for LiOH

LiOH_(s) → Li₂O_(s) + H₂O­_(g) @ 650 ^oC

Carbonates

These can be prepared by bubbling CO₂ through the alkali solution

KOH_(aq) + CO_2(g) → K₂CO_3(aq) + H_2(l)

Crystals of sodium carbonate are efflorescent; they lose water molecules without heating.

Group 1 carbonates are thermally stable except for Lithium.

Li₂CO_3(s) → Li₂O + CO₂

This shows that the thermal stability of group 1 increases as one goes down the group. Lithium has a high polarising power disrupting the carbon – oxygen bond making it easier to break.

Hydrogencarboantes

These can be prepared by bubbling CO₂ through a solution of the carbonate

K₂CO_3(aq) +H₂O_(l)  + CO_{2(g) →} 2KHCO_3(aq)

These decompose to form water and carbon dioxide on heating.

2KHCO_3(aq  → K₂CO_3(aq) +H₂O_(g)  + CO_2(g)

Nitrates

Nitrates can be prepared from the neutralisation reaction between an acid and a base

NaOH + HNO₃ → NaNO₃ + H₂O

Nitrates break down on heating to produce the nitrite and Oxygen

2NaNO_3(s) → 2NaNO_2(s) + O_2(g)

Lithium nitrate decomposes to form the oxide and nitrogen dioxide together with oxygen.

4LiNO_3(s) → 2Li₂O_(g) + 4NO_2(g) + O_2(g)

Sulfates

Sulfate can be prepared using a neutralisation reaction between an acid and a base.

2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

All sulphate are stable to heating

Lithium

Lithium also reacts with Nitrogen just like group 2 metals to form the nitride.

Li_(s) + N_{2(g) →} Li₃N_(s)

All group 1 hydroxides are thermally stable except for LiOH

LiOH_(s) → Li₂O_(s) + H₂O­_(g) @ 650 ^oC

Group 1 carbonates are thermally stable except for Lithium.

Li₂CO_3(s) → Li₂O + CO₂

Lithium nitrate decomposes to form the oxide and nitrogen dioxide together with oxygen.

2LiNO_3(s) → Li₂O_(g) + 2NO_2(g) + O_2(g)