Element of the third period that is expected to exhibit positive electron gain enthalpy is: 

1.	Na	2.	Al
3.	Cl	4.	Ar

The pair that has both members from the same period of the Periodic Table is 

Which one of the following is an isoelectronic pair?

1. ${\mathrm{ClO}}_2^{-}, {\mathrm{ClF}}_2^{+}$

2. ${\mathrm{IF}}_2^{-}, {\mathrm{I}}_3^{-}$

3. ${\mathrm{Cl}}_2\mathrm{O}, {\mathrm{ICl}}_2^{-}$

4. ${\mathrm{ICl}}_2^{-}, {\mathrm{ClO}}_2$

Which species among the following exhibits the highest electron affinity?

1. F^–
2. O^–
3. O
4. Na

The correct order of 3rd ionisation potential of Na, Mg, Al and Si is

1. Si > Al > Mg > Na

2. Mg > Si > Al > Na

3. Mg > Na > Si > Al

4. Mg > Na > Al > Si

The incorrect order of electronegativity is :

Identify the wrong statement in the following:

(1) Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius

(2) Amongst isoelectronic species, greater the negative charge on the anion, larger is the ionic radius

(3) Atomic radius of the elements increases as one moves down the first group of the Periodic Table

(4) Atomic radius of the elements decreases as one moves across from left to right in the 2nd period of the Periodic Table

The ionisation energy will be maximum for the process:

1. $Ba\to B{a}^{2+}$

2. $Be\to B{e}^{2+}$

3. $Cs\to C{s}^{+}$

4. $Li\to L{i}^{+}$

Read the following statements (S) and Explanation (E). Choose the correct answers from the codes (1), (2), (3) and (4):

S : Sulphate is estimated as ${\mathrm{BaSO}}_4$ and not as ${\mathrm{MgSO}}_4$.

E : Ionic radius of ${\mathrm{Mg}}^{2+}$ is smaller than ${\mathrm{Ba}}^{2+}$.

1.  S is correct but E is wrong
2.  S is wrong but E is correct
3.  Both S and E are correct and E is correct explanation of S
4.  Both S and E are correct but E is not correct explanation of S

For the second-period elements, the correct increasing order of first ionisation enthalpy is: