Question

(a) Which two criteria did Mendeleev use to classify the elements in his periodic table?; (b) Which element of period '3' of the modern periodic table; (i) is the most reactive non-metal?; (ii) is the most reactive metal?; (iii) forms ion with -2 charge?; (iv) forms ion with +2 charge?(All India - 2012)

Answer 1

Explanation:

a. atomic masses b.1. argon,2.sodium,3.sulphur,4. magnesium

Answer 2

a. Two criteria that was used by Mendeleev to classify periodic table is

1. atomic mass
2. Recurring occurrence of elements with similar chemical properties

b. Modern periodic table, period 3

i) most reactive non-metal is Chlorine,

ii) most reactive metal is Sodium,

iii) Sulfur forms -2 charge,

iv) Magnesium forms +2 charge

• Period 3 of periodic table has Na, Mg, Al, Si, P, S, Cl, Ar with the atomic number 11,12,13,14,15,16,17 and 18 respectively.
• Non metallic property increases with the increasing atomic number
• Ar (Argon) is inert gas
• Most metallic is Na and non metallic is Cl.