The value of electron gain enthalpy of Na⁺, if IE₁ of Na = 5.1 eV, is:

1. +10.2 eV 

2. –5.1 eV

3. –10.2 eV 

4. +2.55 eV

The formula for the oxide formed by Eka-aluminum is:

1. ${\mathrm{EO}}_4$

2. ${\mathrm{E}}_2{\mathrm{O}}_3$

3. ${\mathrm{E}}_3{\mathrm{O}}_2$

4. EO

Among the elements Ca, Mg, P and Cl, the correct order of increasing atomic radii is:
1. Cl < P < Mg < Ca
2. P < Cl < Ca < Mg
3. Ca < Mg < P < Cl
4. Mg < Ca < Cl < P

In which of the following molecule, the internuclear distance will be maximum:
1. CsI
2. CsF
3. LiF
4. LiI

The first ionization potential of Be and B will be:

1.  8.8 and 8.8
2.  6.6 and 6.6
3.  6.6 and 8.8
4.  8.8. and 6.6

An electronic configuration that has maximum difference between II and III ionization potential is:

1. 1s² 2s² 2p⁶ 3s¹

2. 1s² 2s² 2p⁶ 3s²

3. 1s² 2s² 2p⁶

4. 1s² 2s² 2p⁵

Incorrect order among the following is:

If an atom has electronic configuration 1s²2s²2p⁶3s²3p⁶3d³4s², we will place it in group number:

The correct order of $I^{st}$ IP(ionization potential) among the following elements Be, B, C, N, O is:

The basic theme of the periodic table is: