Group 12 Metals

Alkaline earth metals(Group II)

Group II metals are very reactive metals that have low electronegativity and are readily oxidized, they always exhibit an oxidation state of +2 in their compounds. This is because the outer s electrons are readily lost during a reaction to achieve a noble gas configuration

Melting and boiling point

Melting point generally decreases with Mg decreasing unusually. This is because as the metal ions get larger the distance between the bonding electrons and the positive nucleus gets larger and reduces the overall attraction between the two

Density

Density decreases from Be to Ca and increases from Ca to Ba

Atomic radius

The atomic radius increases going down the group because going down the group, each succeeding elements have one more shell of electrons. The distance between the nucleus and outer electrons are further apart from each other

First ionization energy

The first ionization energy decreases down the group because the distance between the nucleus and outer electrons increase, and the outer electrons are more shielded

Electronegativity

Electronegativity decreases down the group because the distance between the nucleus and the bonded pair of electrons increases down the group. Therefore the electrons are held less strongly by the nucleus

Reaction with oxygen gas

All Group II elements(except beryllium) burn in oxygen with a bright flame to form monoxides.

2M(s) + O2(I) = 2MO(s)

Magnesium burns with brilliant white flame
Calcium burns with brick red flame
Strontium burns with crimson red flame
Barium burns with apple green flame

Reaction with water

All Group II elements(except beryllium) Reacts with water to form hydroxides

M(s) + 2H20(I) = M(OH)2(aq) + H2(g)

Beryllium has no reaction with cold water or steam due to the formation of protective oxide layer on its surface
Magnesium reacts very slowly with cold water, taking several days to collect a test tube of hydrogen gas and a wealthy alkaline magnesium hydroxide and hydrogen gas

Mg(s) + 2H20(I) = Mg(OH)2(aq) + H2(g), very slow

However, it reacts rapidly with steam to produce magnesium hydroxide and hydrogen gas

Mg(s) + 2H20(g) = MgO(s) + H2(g), very fast

Calcium, Strontium and Barium reacts vigorously with cold water to give hydroxides

Ca(s) + 2H20(I) = Ca(OH)2(aq) + H2(g)

Sr(s) + 2H20(I) = Sr(OH)2(aq) + H2(g)

Ba(s) + 2H20(I) = Ba(OH)2(aq) + H2(g)

The reactivity of the elements with water increases down the group, in other words, they become more soluble down the group

Solubility

The solubility of Group II hydroxides increases down the group, however the solubility of Group II sulfates decreases down the group

Group II carbonates

Group II carbonates do not react with water
Group II carbonates react with sulfuric acid, Nitric acid and dilute hydrochloric acid to form salt, water and carbon dioxide and the solubility decreases down the group

MCO3(s) + H2SO4(aq) = MSO4(aq) + H20(I) + CO2(g)

MCO3(s) + HNO3(aq) = M(NO3)2(aq) + H20(I) + CO2(g)

MCO3(s) +2HCL(aq) = MCl2(aq) + H20(I) + CO2(g)

Thermal decomposition of Group II salts

Thermal decomposition gets more stable down the group
Thermal stability of Group II nitrates increases down the group. This is because the cation size increases down the group

2M(NO3)2(s) = 2MO(s) + 4NO2(g) + O2(g)

Thermal stability of Group II carbonates increases down the group because the cation size increases down the group.

MCO3(s) = MO(s) + CO2(g)

Group 2 summary

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