## Classification of Elements and Periodicity in Properties Questions and Answers Part-10

1. The ionic radii of $N^{3-},O^{2-} and F^{-}$   are respectively given by
a) 1.36, 1.40, 1.71
b) 1.36, 1.71, 1.40
c) 1.71, 1.40, 1.36
d) 1.71, 1.36, 1.40

Explanation: The ionic radii must follow the order $N^{3-},O^{2-} and F^{-}$

2. The first ionisation potential of aluminium is smaller than that of magnesium because
a) Atomic size of Al > Atomic size of Mg.
b) Atomic size of Al < Atomic size of Mg
c) Al has one electron in p - orbital
d) None of these

Explanation: Al ( 3s2p1) and Mg (3s2). Lower energy is required to remove 3p1 electron than 3s1 electron (penetrating effect is s > p > d > f ) . Secondly Mg has stable electronic configuration than Al

3. Which of the following halides is not oxidized by  $MnO_{2}$
a) $F^{-}$
b) $CI^{-}$
c) $Br^{-}$
d) $I^{-}$

Explanation: F2 is strongest oxidising agent. F- is not oxidised by MnO2

4. Which species has the maximum ionic radius
a) $Na^{+}$
b) $O^{2-}$
c) $F^{-}$
d) $Mg^{2+}$

Explanation: O2- has minimum effective nuclear charge, hence has maximum ionic radius

5. The valence shell of element A contains 3 electrons while thevalence shell of element B contains 6 electrons . If A combines with B, the probable formula of the compound formed will be
a) $AB_{2}$
b) $A_{2}B$
c) $A_{2}B_{3}$
d) $A_{3}B_{2}$

Explanation: The element A is ns2p1 and B is ns2p4. They can form compound of the type A2B3

6. Pauling scale of electronegativity of elements helps to determine
a) covalent nature of an element
b) position of an element in EMF series
c) dipole moment of molecules
d) polarity of bond

Explanation: Pauling scale of electronegativity helps to determine polarity of bond

7. The statement that is not correct for the periodic classification of elements is
a) The properties of elements are the periodic functions of their atomic number
b) Non-metallic elements are lesser in number than metallic elements
c) The first ionization energies of elements along a period do not vary in a regular manner with increase in atomic number
d) For transition elements the d-sub shells are filled with electrons monotonically with increase in atomic number

Explanation: For transition elements the d-sub shells are filled with electrons monotonically with increase in atomic number

8. Which is coloured ion
a) $\left[Cu\left(NH_{3}\right)_{4}\right]^{+}$
b) $\left[Cu\left(NH_{3}\right)_{4}\right]^{2+}$
c) $\left[Zn\left(H_{2}O\right)_{6}\right]^{2+}$
d) $\left[Ca\left(H_{2}O\right)_{6}\right]^{2+}$

Explanation: Due to presence of one unpaired electron (Cu2+ = 3p6d9 ) the complex $\left[Cu\left(NH_{3}\right)_{4}\right]^{2+}$   is coloured

9. Considering the elements from left to right in the second period of the periodic table, the gram atomic volume of the elements
a) first increases then decreases
b) decreases
c) increases at constant rate
d) remains unchanged