Which of the following oxides is most acidic in nature?

1.${\mathrm{Na}}_2\mathrm{O}$

2. MgO

3.${\mathrm{SiO}}_2$

4. ${\mathrm{Cl}}_2{\mathrm{O}}_7$

Match Column-I with Column-II.

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

The first ionization enthalpy of sodium (Na) is 5.1eV. Using this information, determine the value of the electron gain enthalpy of \(\mathrm{Na^+}\):

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

Which of the following molecules, has the internuclear distance 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

Which of the following electronic configuration has maximum difference between II and III ionization potential?

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: