Lyophilic sols(solvent loving): They are those in which the dispersed phase exhibits a definite affinity for the dispersion medium(liquid) or the solvent.

For eg. Dispersion of starch, gum, and protein in water.

The affinity of sol particles for the medium is due to hydrogen bonding with water(dispersion medium). They may have little or no charge at all and they do not exhibit Tyndall effect.

These sols are reversible in nature i.e., if two constituents of the sol are separated by any means (such as evaporation), then the sol can be prepared again by simply mixing the dispersion medium with the dispersion phase and shaking the mixture

PCl₃ ( Phosphorus trichloride ) gets easily hydrolysed in water or , moisture present in air , forming  HCl gas as per following reaction ,

PCl₃     +     3 H₂ O  ----------->    H₃ PO₃   +   3HCl

Thus ,  HCl gas  produced is highly soluble in water .  It forms a mist of droplets of  hydrogen chloride . These  droplets , thereafter    get  mixed with atmospheric vapours to form a mist which appears as white fumes.

An atom is the basic unit of an element. It is a form of matter which can not be  further broken down by any physical or chemical means. A typical atom consists of protons , electrons and neutrons.

Further , there are many conceptual details about the ' Structure of an atom ' , which are and have been explained to students at class 12 level. It  would , therefore , be desirable to post  a question  , if any , concerning specific  aspects    about the atom . 

The extent of covalency  is usually inferred by the polarising power  / polarisation of bonds in a   a covalent compound. The polarising power in a covalent compound depends upon the charge or oxidation state of the central atom .The atoms of Group 15 elements  ( except N ) form both tri and pentahalides .  These atoms  are , therefore , termed as central atom  , and have have large polarising power than the halogen atom attached to them . Thus, higher the oxidation state of central atom  more is the polarising power. Accordingly, 

 , in pentahalides the oxidation state of central atom  is  +5  , while in trihalide it is +3 . Therefore ,   pentahalides are more covalent than a trihalide. 

C₂ H₅ NH₂ is more basic than CH₃ NH₂  .

Reasons  for higher basic nature of  ethyl amine  are   ,

(i) ethyl group  exhibits greater +I effect than methyl  group.

(ii)  The electron density over N atom in ethyl group increases , as compared to that of  N over methyl group.

So,  N in ethyl group is capable of donating more electrons (or electron pairs )  thereby exhibiting more basic nature of ethyl amine.

Chlorine has higher electron gain enthalpy than fluorine because due to small size of fluorine some energy is utilized in overcoming the force of repulsion among electrons. Hence it has lesser value of electron affinity.

Bananas are picked when green and artificially ripened after shipment by being gassed with ethylene. Calcium carbide is also used in some countries for artificially ripening fruit.