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

Lanthanoid contraction is caused due to :

1. the appreciable shielding on outer electrons by 4f electrons from the nuclear charge

2. the appreciable shielding on outer electrons by 5d electrons from the nuclear charge

3. the same effective nuclear charge from Ce to Lu

4. the imperfect shielding on outer electrons by 4f electrons from the nuclear charge

In the transition elements, the incoming electron occupies (n-1)d sublevel in preference to:

1. np

2. ns

3. (n-1)d

4. (n+1)s

The electronegativity of elements from group 1 to group 17 :

1. Decreases

2. Increases

3. Remains constant

4. All of the above

The electronic configuration of the most electropositive element is :

1. [He]2s¹

2. [Xe]6s¹

3. [He]2s²

4. [Xe]6s²