The position of certain elements in the Modern Periodic Table are shown below.

Using the above table answer following questions giving reasons in each case:

(i) Which element will form only covalent compounds?

(ii) Which element is a non-metal with valency 2?

(iii) Which element is a metal with valency 2?

(iv) Out of H, C and F which has largest atomic size?

(v) To which family does H, C and F belong?

OR

Define atomic size. Give its unit of measurement. In the modern periodic table what trend is observed in the atomic radius in a group and a period and why is it so?

(i) E

(II) B

(III) D

(IV) F

(V) Halogen

OR

Atomic radius is defined as the distance from the center of the nucleus to the boundary of the surrounding cloud of electrons. The atomic radius can be further specified into 4 types as:

Covalent radius: half the distance between two atoms of a diatomic compound, singly bonded.

Van der Waals radius: half the distance between the nuclei of atoms of different molecules in a lattice of covalent molecules.

Metallic radius: half the distance between two adjacent nuclei of atoms in a metallic lattice.

Ionic radius: half the distance between two nuclei of elements of an ionic compound.

This term is measured in Angstroms or picometers (pm).

Atomic radius decreases from left to right within a period. This is caused by the increase in the number of protons and electrons across a period. One proton has a greater effect than one electron; thus, electrons are pulled towards the nucleus, resulting in a smaller radius.

Atomic radius increases from top to bottom within a group. This is caused by addition of new shell.