Which of the following exhibits variable oxidation states?

1.	Na	2.	Cu
3.	Mg	4.	Al

The lightest metal in the periodic table is:

1. H

2. Mg

3. Ca

4. Li

The electronic configuration that represents the d-block element is: 

1. 1s² 2s² 2p⁶ 3s²3p⁶3d¹⁰ 4s²4p⁶

2. 1s² 2s² 2p⁶ 3s²3p⁶3d¹⁰ 4s²4p¹

3. 1s² 2s² 2p⁶ 3s²3p⁶3d¹⁰ 4s²

4. 1s² 2s² $2p^6$ 3s²3p⁶ 4s²

The most common oxidation state of cerium (Ce) is:

1. +5, +3

2. +5, +4

3. +3, +4

4. +3, +5

Which of the electronic configuration of an atom has the lowest ionization enthalpy? 

1. 1s²,2s²2p⁵

2. 1s²,2s²2p³

3. 1s²,2s²2$p^6$,3s¹

4. 1s²,2s²2p⁶

The difference between ions and atoms is of:

1. relative size

2. Configuration

3. presence of charge

4. All of these

The expected trend of change in atomic radius down the group is:

1. Continuous decrease

2. Continuous increase

3. Periodic one, an increase followed by a decrease

4. Periodic one, a decrease followed by an increase

An element R forms the highest oxide R₂O₅. R belongs to:

1. 13th  group

2. 15th group

3. 16 th group

4. 2nd group

Amongst the following electronic configurations, the highest ionization energy
is represented by:

1. [Ne]3s²3p³

2. [Ne]3s²3p²

3. [Ar]3d¹⁰4s²4p³

4. [Ne]3s²3p¹

Which pair of elements is chemically most similar?

1. Na, Al

2. Cu, S

3. Ti, Zr

4. Zr, Hf