Isoelectronic pair among the following is

• Ca and K

• Ar and Ca²⁺

• K and Ca²⁺

• Ar and K

On adding 1 g arsenic to 80 g benzene, the freezing' point of benzene is lowered by 0.19°C. The formula of arsenic is

• As

• As₂

• As₃

• As₄

When a metal atom combines with a non-metal atom, the non-metal atom will

• lose electrons and decrease in size

• lose electrons and increase in size

• gain electrons and decrease in size

• gain electrons and increase in size 

Born-Haber cycle can be used to estimate

• electronegativity

• electron affinity

• ionic radii

• All of these

Which is heaviest ?

• 25g mercury

• 2 mol carbon dioxide

• 2 mol water

• 4 g-atom of oxygen

The correct order of electron affinity of oxygen, sulphur, chlorine, fluorine is

• S < O < Cl < F

• S < O < F < Cl

• O < S < F < Cl

• O < S < Cl < F

The metal which deposits copper from copper sulphate solution is

• gold

• iron

• platinum

• mercury

On Pauling scale, the electronegativity of an element is measured by using

• ${\mathrm{\chi }}_{\mathrm{A}} - {\mathrm{\chi }}_{\mathrm{B}} = \sqrt{∆}$

• ${\mathrm{\chi }}_{\mathrm{A}} - {\mathrm{\chi }}_{\mathrm{B}} = 0.208 \sqrt{∆}$

• ${\mathrm{\chi }}_{\mathrm{A}} + {\mathrm{\chi }}_{\mathrm{B}} = 0.208 \sqrt{∆}$

• ${\mathrm{\chi }}_{\mathrm{A}} - {\mathrm{\chi }}_{\mathrm{B}} = 0.208 {∆}^2$

369.

There is a general understanding of ionic radius based on the nuclear charges and the number of electrons surrounding the nucleus which generally works very well. Which one of the following represents the correct decreasing order ofionic radius for C^4-, N^3-, O^2- and F^-?

• C^4- > N^3- > O^2- > F^- 

• F^-> O^2- > N^3- > C^4-

• O^2- > N^3- > C^4- > F^-

• F^- > N^3- > C^4- > O^2-

What is the name of the element with atomic number 105?

• Dubnium

• Holmium

• Kurchatovium

• Nobelium