Following statements regarding the periodic trends of chemical reactivity of the alkali metals and the halogens are given. Which of these statements gives the correct picture? 

• The reactivity decreases in the alkali metals but increases in the halogens with increase in atomic number down the group

• In both the alkali metals and the halogens the chemical reactivity decreases with increase in atomic number down the group

• Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens

• Chemical reactivity increases with increase in atomic number down the group in both the alkali metals and halogens

In a multi-electron atom, which of the following orbitals described by the three quantum numbers will have the same energy in the absence of magnetic acid and electric fields?

(a) n = 1, l = 0, m = 0
(b) n = 2, l = 0, m = 0
(c) n = 2, l = 1, m = 1
(d) n = 3, l = 2, m = 1
(e) n = 3, l = 2, m = 0

• (a) and (b)

• (b) and (c)

• (c) and (d)

• (c) and (d)

In which of the following arrangements the order is NOT according to the property indicated against it?

• Al³⁺ < Mg²⁺ < Na⁺ < F^- Increasing ionic size

• B < C < N < O Increasing first ionization enthalpy

• I < Br < F < Cl Increasing electron gain enthalpy (with negative sign)

• I < Br < F < Cl Increasing electron gain enthalpy (with negative sign)

Which of the following statements in relation to the hydrogen atom is correct?

• 3s orbital is lower in energy than 3p orbital

• 3p orbital is lower in energy than 3d orbital

• 3s and 3p orbitals are of lower energy than 3d orbital

• 3s and 3p orbitals are of lower energy than 3d orbital

Which one the following ions has the highest value of ionic radius?

• Li⁺

• F^-

• O^2-

• O^2-

Which of the following atoms should have the highest I^st electron affinity?

• F

• O

• N

• C

The decreasing order of basic character of K₂O, BaO, CaO and MgO is

• K₂O > BaO > CaO > MgO

• K₂O > CaO > BaO > MgO

• MgO > BaO > CaO > K₂O

• MgO > CaO > BaO > K₂O

Among Be, B, Mg and Al, the second ionisation potential is maximum for

• B

• Be

• Mg

• Al

19.

In case of heteronuclear diatomics of the type AB, where A is more electronegative than B, bonding molecular orbital resembles the character of A more than that of B. The statement

• is false

• is true

• cannot be evaluated since data is not sufficient

• is true only for certain systems

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