Q.What happens when magnesium metal is burnt in air?

Alkaline earth metals have outer configuration ns² (e.g. Mg: [Ne]3s²).

Group 2 elements (Be, Mg, Ca, Sr, Ba, Ra) are called alkaline earth metals. Each has exactly two electrons in its outermost s-orbital and a filled noble-gas core beneath, giving the general valence config …

False. Mg gives no flame colour, but Ca gives a brick-red flame -- so it is not true that 'both' fail to colour the flame.

Alkaline earth metals (Group 2) show flame colouration when their outer electrons are thermally excited in a flame and then fall back to the ground state, emitting visible light of a characteristic wavelength.

• Beryllium and Magnesium do NOT impart any colour to the flame. Their ions (Be2+, Mg2+) are small with high ionisation/excitation energy, so the flame's thermal energy is insufficient to excite their electrons to emit visible light. …

Calcium is the most abundant of the Group 2 (alkaline earth) metals in the earth's crust.

The alkaline earth metals are the Group 2 elements: beryllium, magnesium, calcium, strontium, barium and radium. Ranked by natural abundance in the earth's crust, calcium is the 5th most abundant element overall (about 3.6% by mass), occurring widely as limestone/calcite (CaCO3), gypsum (CaSO4.2H2O) and fluorspar (CaF2). This makes it more abund …

Higher charge (+2) and smaller size give alkaline earth cations much greater charge density than alkali metal cations, so they bind ligands and form complexes more readily.

Complex formation requires a metal cation to attract and hold electron-pair-donating ligands around itself. How strongly a cation can do this depends on its charge density (charge/size), also called polarising power.

Alkaline earth metals (Group 2) form M^2+ ions that carry twice the positive charge of the corresponding alkali metal's M+ ion (Group 1), while also being smaller in ionic radius than the alkali metal ion of the same period (due to the higher effective nuclear charge across the period). This combination -- higher charge PLUS smaller size -- gives alkaline earth cations a substantially higher charge density than alkali metal cations.

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Hydroxide solubility of Group 2 metals increases down the group (Be(OH)2 least soluble, Ba(OH)2 most).

For an ionic solid to dissolve, its lattice energy (which holds the ions together in the solid) must be overcome, largely by the hydration energy released as the ions become surrounded by water molecules.

Going down Group 2 (Be -> Mg -> Ca -> Sr -> Ba), the cation size increases steadily. Both lattice energy and hydration energy decrease as ionic size increases, but for these hydroxides, lattice energy falls off FASTER than hydration energy (because the hydroxide ion OH- is relatively small and fixed in size, so the increasing cation size matters more for lattice energy than for the comparatively smaller drop in hydration energy). As a net result, the balance tips increasingly in favour of dissolution as the group is descended, so solubility of the hydroxides increases down the group: Be(OH)2 and Mg(OH)2 are only …

Slaked lime = calcium hydroxide, Ca(OH)2, made by adding water ('slaking') to quicklime (CaO).

Quicklime (calcium oxide, CaO) is produced by strongly heating (calcining) limestone, CaCO3. When water is added to quicklime, an exothermic reaction ('slaking') occurs, producing calcium hydroxide:

CaO(s) + H2O(l) -> Ca(OH)2(s) …

Magnesium is the s-block metal used to make Grignard reagents (R-Mg-X).

Grignard reagents are organomagnesium halide compounds of the general formula R-Mg-X (where R is an alkyl or aryl group and X is a halogen, usually Cl, Br or I). They are prepared by reacting an alkyl or aryl halide with magnesium metal turnings in a dry ether solvent (anhydrous conditions are essential, since Grignard reagents react instantly with water/moisture):

R-X + Mg --(dry ether)--> R-Mg-X …