Periodic Classification and Elements

28 elements are present in the long form of the periodic table

32 elements are present in the 6th period of modern periodic table

63 elements were known when mendeleev classified the elements

Li & Be are metals among the first ten elements

AS ELEMENT X BELONGS TO GROUP 2 , ITS VALENCY IS 2

each new period in the periodic tabl represents +1 shell

AS IT BELONGS TO GROUP 15 , IT VALENCY WOULD BE 3 (8-5) .

18 elements are present in the 5th period of the periodic table

7 periods are present in the modern periodic table

Nitrogen atom acquires three electrons to form a nitride ion.

Phosphorus has the electronic configuration 1s² 2s² 2p⁶ 3s² 3p³. It needs three electrons to attain stable noble gas configuration of argon.

Correct answer. Given electronic configuration of tungsten is incorrect. Correct electronic configuration of tungsten (₇₄W) is [Xe] 4f¹⁴ 5d⁴ 6s².

Correct answer. Electronic configuration of gadolinium (₆₄Gd) is [Xe] 4f⁷ 5d¹ 6s².

Total number of orbitals in a shell with principal quantum number ‘n’ is n².

Palladium (₄₆Pd): [Kr] 4d¹⁰ 5s⁰ Cadmium (₄₈Cd): [Kr] 4d¹⁰ 5s² Both Pd and Cd have completely filled 4d-orbital.