Classification of Elements and Periodicity in Properties

The ground state electronic configuration of CO molecule is

• 1σ²2σ²1$\mathrm{\pi }$⁴3σ²

• 1σ²2σ²3σ²1$\mathrm{\pi }$²2$\mathrm{\pi }$²

• 1σ²2σ²1$\mathrm{\pi }$²3σ²2$\mathrm{\pi }$²

• 1σ²1$\mathrm{\pi }$²2σ²2σ²

If the first ionization energy of H atom is 13.6 eV, then the second ionization energy of He atom is

• 27.2 eV

• 40.8 eV

• 54.4 eV

• 108.8 eV

An f-shell containing 6 unpaired electrons can exchange

• 6 electrons

• 9 electrons

• 12 electrons

• 15 electrons

The correct order of first ionisation enthalpies of the following elements is

• Be > Mg > Ca > Sr > Ra > Ba

• Ra > Ba > Sr > Ca > Mg > Be

• Be > Mg > Ca > Sr > Ba > Ra

• Ra > Sr > Ba > Mg > Ca > Be

'Hydride Gap' is referred to which region of the Periodic Table ?

• Groups 3, 4 and 5

• Groups 5, 6 and 7

• Groups 4, 5 and 6

• Groups 7, 8 and 9

In which one of the following pairs the radius of the second species is greater than that of the first?

• Na, Mg

• O^2-, N^3-

• Li⁺, Be²⁺

• Ba²⁺, Sr²⁺

Number of unpaired electrons in sulphur is

• 2

• 6

• 8

• 1

Which of the following is correct?

• The number of electrons present in the valence shell of S in SF₆ is 12.

• The rates of ionic reactions are very slow

• According to VSEPR theory, SnCl₂ is a linear molecule.

• The correct order of ability to form ionic compounds among Na⁺, Mg²⁺ and Al³⁺ is  Al³⁺ >Mg²⁺ >Na⁺.

The atomic numbers of elements A, B, C and D are Z - 1; Z; Z + 1 and Z + 2, respectively. If 'B' is a noble gas, choose the correct answers from the following statements-

1) 'A' has higher electron affinity.

(2) 'C' exists in +2 oxidation state. 

(3) 'D' is an alkaline earth metal.

• (1) and (2)

• (2) and (3)

• (1) and (3)

• (1), (2) and (3)

Which of the following does not exhibit the periodicity in properties of the elements?

• Ionisation energy

• n/p ratio

• Electronegativity

• Atomic radius