The incorrect order of electronegativity is :

1.	Cl > S > P > Si	2.	Si > Al > Mg > Na
3.	F > Cl > Br > I	4.	None of the above.

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

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:

Which one of the following orders is not in accordance with the property stated against?

1. $F_2>C{l}_2>B{r}_2>I_2$ $:$ $Oxidi\sin g$ $power$

2. $Hl>HBr>HCl>HF$ $:$ $Acidic$ $property$ $in$ $water$

3. $F_2>C{l}_2>B{r}_2>I_2$ $:$ $Electronegativity$

4. $F_2>C{l}_2>B{r}_2>I_2$ $:$ $Bond$ $dissociation$ $energy$

Identify the correct order of the size of the following:

1. $C{a}^{2+}<K^{+}<Ar<S^{2-}<C{l}^{-}$

2. $C{a}^{2+}<K^{+}<Ar<C{l}^{-}<S^{2-}$

3. $Ar<C{a}^{2+}<K^{+}<C{l}^{-}<S^{2-}$

4. $C{a}^{2+}<A{r}^{+}<K^{+}<C{l}^{-}<S^{2-}$

Among the following, the most characteristic oxidation states for lead and tin are, respectively:

1. +4, +2

2. +2, +4

3. +4, +4

4. +2, +2

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

Which ion is isoelectronic with Be²⁺?
1. $H^{+}$
2. $L{i}^{+}$
3. $N{a}^{+}$
4. $M{g}^{2+}$