Group 1

group 1 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 à 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 à 2K2O

K + O2 à KO2

2K + O2 à K2O2

With H2O

2Li(s) + 2H2O(l) à 2LiOH(aq) + H2(g)

2Na(s) + 2H2O(l) à 2NaOH(aq) + H2(g)

2K(s) + 2H2O(l) à 2KOH(aq) + H2(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) à Li2O(s) + H2(g) @ 650 oC

Carbonates

These can be prepared by bubbling CO2 through the alkali solution

KOH(aq) + CO2(g) à K2CO3(aq) + H2(l)

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

Group 1 carbonates are thermally stable except for Lithium.

Li2CO3(s) à 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

K2CO3(aq) +H2O(l)  + CO2(g) à 2KHCO3(aq)

These decompose to form water and carbon dioxide on heating.

2KHCO3(aq  à  K2CO3(aq) +H2O(g)  + CO2(g)

Nitrates

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

NaOH + HNO3 à NaNO3 + H2O

Nitrates break down on heating to produce the nitrite and Oxygen

2NaNO3(s) à 2NaNO2(s) + O2(g)

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

2LiNO3(s) à Li2O(g) + 2NO2(g) + O2(g)

Sulfates

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

2NaOH + H2SO4 à 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) + N2(g) à Li3N(s)

All group 1 hydroxides are thermally stable except for LiOH

LiOH(s) à Li2O(s) + H2(g) @ 650 oC

Group 1 carbonates are thermally stable except for Lithium.

Li2CO3(s) à Li2O + CO2

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

2LiNO3(s) à Li2O(g) + 2NO2(g) + O2(g)

 

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