Which of the following has the least density?

(1)Na

(2)Li

(3)Mg

(4)K

An element R forms an oxide with the formula R₂O₅, where R shows its highest oxidation number. To which group does the element R belong in the periodic table?

1. Group 14
2. Group 15
3. Group 16
4. Group 17

Transition elements exhibit variable oxidation states because they release electrons from the following orbits:

1. ns and np orbits

2. (n-1)d and ns orbits

3. (n-1)d orbits

4. ns orbits

In the II period, the most acidic oxide is formed by:

1. F

2. N

3. O

4. Li

The outer electronic configuration of Gd (Atomic no. 64) is:

(1) 4f³ 5d⁵6d²

(2) 4f⁸ 5d¹⁰6d²

(3) 4f⁴ 5d⁴6d²

(4) 4f⁷ 5d¹6s²

Which of the following transition metal ions has the lowest density?

(a) Copper

(b) Nickel

(c) Scandium

(d) Zinc

Ionic radii are :

(1) Inversely proportional to effective nuclear charge.

(2) Inversely proportional to square of effective nuclear charge.

(3) Directly proportional to effective nuclear charge.

(4) Directly proportional to square of effective nuclear charge.

Which one is a metalloid?

(1)Tin

(2)Germanium

(3)Sulphur

(4)Carbon

Elements with electronic configuration 1s²,2s²2p⁶, 3s²3p⁶3d¹⁰, 4s²4p⁶4d¹⁰, 5s²5p³ belongs to the ...... group of periodic table.

1. 3^rd

2. 15^th

3. 17^th

4. 12^th

General electronic configuration of the transition elements is given by:

(1) ns²nd^1-10

(2) ns²np⁶nd^1-10

(3) (n-1)d^1-10np⁶

(4) (n-1)${\mathrm{d}}^{1-10}$n$s^{1-2}$