Out of the following pairs of electrons, identify the pairs of electrons present in degenerate orbitals.

(a).	(i)  n=3, l=2, ml=-2, ms=-\(\frac{1}{2}\)	(ii) n=3, l=2, ml=-1, ms=-\(\frac{1}{2}\)
(b).	(i) n=3, l=1, ml=+1, ms=+\(\frac{1}{2}\)	(ii) n=3, l=2, ml=+1, ms=+\(\frac{1}{2}\)
(c).	(i) n=4, l=1, ml=+1, ms=+\(\frac{1}{2}\)	(ii) n=3, l=2, ml=+1, ms=+\(\frac{1}{2}\)
(d).	(i) n=3, l=2, ml=+2, ms=-\(\frac{1}{2}\)	(ii) n=3, l=2, ml=+2, ms=+\(\frac{1}{2}\)

1. (a), (d)

2. (b), (c)

3. (c), (d)

4. (b), (d)

The correct set of quantum numbers among the following is - 

         n       l      m

(a)     1      1        +2

(b)     2      1       +1

(c)     3      2        -2

(d)     3      4        -2

1. (a), (d)

2. (b), (c)

3. (c), (d)

4. (b), (d)

An isoelectronic pair among the following is -

(a) Na⁺, Mg²⁺ 

(b) Al³⁺, O^- 

(c) Na⁺, O^2- 

(d) N^3-, Cl^- 

1. (a), (c)

2. (b), (c)

3. (c), (d)

4. (b), (d)

The correct statement(s) among the following regarding quantum numbers is -

1. (a), (d)

2. (b), (c)

3. (c), (d)

4. (b), (d)

Identify the pairs which are not of isotopes?

(a) ${}_6{}^{12}\mathrm{X}, {}_6{}^{13}\mathrm{Y}$

(b) ${}_{17}{}^{35}\mathrm{X}, {}_{17}{}^{37}\mathrm{Y}$

(c) ${}_6{}^{14}\mathrm{X}, {}_7{}^{14}\mathrm{Y}$

(d) ${}_4{}^8\mathrm{X}, {}_5{}^8\mathrm{Y}$

1. (a), (d)

2. (b), (c)

3. (c), (d)

4. (b), (d)

The electronic configuration of the element which is just above the element with atomic number 43 in the same group is ______.

1. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{5}4{\mathrm{s}}^2$

2. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{5}4{\mathrm{s}}^{3}4{\mathrm{p}}^6$

3. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{6}4{\mathrm{s}}^2$

4. $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}3{\mathrm{d}}^{7}4{\mathrm{s}}^2$

Comprehension given below is followed by some multiple choice questions. Each question has one correct option. Choose the correct option.

In the modern periodic table, elements are arranged in order of configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four block, viz s, p, d and f.

The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Aufbau principle, the seven periods (1 to 7) have 2, 8, 8, 18, 18, 32 and 32 elements respectively.

The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids are placed at the bottom of the periodic table

(i) The element with atomic number 57 belongs to 

1. s-block

2. p-block 

3. d-block

4. f-block

The statement that is not correct for periodic classification of elements is: