(i) Why do we classify elements ?
(ii) What are the two criteria used in the development of Modern Periodic Table ?
(iii) State the position of (a) metals, (b) non-metals and ( c) metalloids in the periodic table.
(iv) Would you place two isotopes of chlorine, Cl-35 and Cl-37 in different slots of the periodic table because of their different atomic masses or in the same slot because their chemical properties are same ? Justify your answer.

Explanation

(i) To study the properties of elements and to keep the elements with similar properties together.
(ii) Chemical properties of elements and atomic number.
(iii) Metals lies on extreme left, metalloids lie in the middle and non-metals lie on the right side.
(iv) They should be placed in the same slot. Since they have same numbers of electrons.