Bond energy is the amount of energy required to dissociate one mole of bonds present between the atoms in the gaseous phase. As the molecules dissociate completely into atoms in the gaseous phase therefore bond energy of a diatomic molecule is called enthalpy of atomisation.

The process by which simple molecules join together to form large molecules is known as polymerization.
Simple alkenes polymerize to form long chain addition polymers.
For example, ethylene gives polyethylene.

The blue colour of the solution is due to ammoniated electron which absorbs energy in the visible region of light and imparts blue colour
Na⁺(am) + e^-(am) + NH₃(l) \(\longrightarrow \) NaNH₂(am) + \(\frac { 1 }{ 2 } \)H₂(g)

Zn(s) + Cu²⁺(aq) \(\rightarrow\) Zn²⁺(aq) + Cu(S)

Acid rain is the rain water mixed with small amount of sulphuric acid, nitric acid along with hydrochloric acid which are formed from the oxides of sulphur and nitrogen present in air as pollutants. It has a pH of 4-5.
Harmful effects of Acid Rain
(i) It is toxic to vegetation and aquatic life.
(ii) It damages buildings and statues. Taj Mahal has been damaged by acid rain.
(iii) Acid rain corrodes water conducting pipes resulting in the leaching of heavy metals such as iron, lead, etc., to the drinking water.

According to de Broglie equation, \(\lambda =\frac { h }{ mv } \)
Momentum of electron, mv =\(\frac { h }{ \lambda } =\frac { (6.626\times 10^{ -34 }kg \ m^{ 2 }s^{ -1 } }{ (5200\times 10^{ -10 }m) } \)
= 1.274 x 10^-27 kg ms^-1 ...(i)
The momentum of electron can also be calculated as = mv = (9.1 x 10-31 kg) x v
Comparing (i) and (ii) ...(ii)
(9.1 x 10^-31 kg) x v = (1.274 x 10^-27 kg ms^-1)
v = \(\frac { (1.274\times 10-27kgms-1) }{ (9.1x10^{ -31 }kg) } \) = 1.4\(\times \)10³ms^-1

Many transition and inner-transition metals absorb hydrogen into the interstices of their lattices to yield metal like hydrides also called the interstitial hydrides. These hydrides are generally non-stoichiometric and their composition vary with temperature and pressure.
For example, TiH_1.73, CeH_2.7

(a) \(_{ 92 }^{ 233 }{ U }\)
(b) \(^{ 9 }{ Be }\)

Ar has 18 electrons.

At high pressure, the real gas shows large deviations from ideal behaviour as the curves are far apart.