Chemistry MCQs for NEET — Practice Questions with Answers

Bohr model is only valid for 1e^- system.

1/$\mathrm{\lambda }$ = RZ² [ 1/n₁² - 1/n₂²] = R x 2² [ 1/1² - 1/2²]

1/$\mathrm{\lambda }$ = R x 4[3/4]; 1/$\mathrm{\lambda }$ =3R; [ $\mathrm{\lambda }$ = 1/3R]

No. of protons $\to$13-7 = 6

No. of protons = Atomic no = 6

10

4.

(d) (a) According to de-Broglie's equation

Wavelength ($\mathrm{\lambda }$) = h/mv

where, h = Planck's constant

Thus, statement (a) is correct.

(b) According to Heisenberg uncertainty principle, the uncertainties of position($∆x$) and momentum (p=m$∆$v) are related as 

$$\begin{gathered} ∆x.∆\mathrm{p}\ge \mathrm{h}/4\mathrm{\pi } \mathrm{or} ∆x.\mathrm{m}∆\mathrm{v}\ge \mathrm{h}/4\mathrm{\pi } \\ ∆x.\mathrm{m}∆\mathrm{a}.∆\mathrm{t}\ge \mathrm{h}/4\mathrm{\pi } [∆\mathrm{v}/∆\mathrm{t} =∆\mathrm{a}, \mathrm{a}=\mathrm{acceleration}] \\ \mathrm{or} ∆x.\mathrm{F}.∆\mathrm{t}\ge \mathrm{h}/4\mathrm{\pi } [{.}_{.}. \mathrm{F} = \mathrm{m}.∆\mathrm{a}] \\ \mathrm{or} ∆\mathrm{E}.∆\mathrm{t}\ge \mathrm{h}/4\mathrm{\pi } [... ∆\mathrm{E} = \mathrm{F}.∆x, \mathrm{E}=\mathrm{energy}] \end{gathered}$$

Thus, statement (b) is correct.

(c) The half and fully filled orbitals have greater stability due to greater exchange energy, greater symmetry and more balanced arrangement. Thus statement (c) is correct.

(d) For a single electronic species like H, energy depends on value of n and does not depend on l. Hence energy of 2s-orbital and 2p-orbital is equal in case of hydrogen like species. Therefore, statement (d) is incorrect.

(b) The element with atomic number, Z = 114 is flerovium (Fl). It is a super heavy artificial chemical element. In the periodic table of the elements, it is transactinide element in the p-block. It is a member of 7th period and is the heaviest known member of the carbon family.

Electronic configuration for Z =114 is

        [Rn]₈₆5f¹⁴,6d¹⁰,7s²,7p²

(b)

We know that n=3, l=1 is for 3p-orbital,so maximum 6 electrons can be filled.

The d_z² and d_x²-y² orbitals have electron density along the x, y, and z axes. The d_z² orbital has a dumbbell shape with electron density along the z-axis, while the d_x²-y² orbital has a double dumbbell shape with electron density along the x and y axes.

(c) Two electrons occupying the same orbital has equal spin but the directions of their spin are opposite. Hence, spin quantum number s (represented +1/2 and -1/2) distinguishes them.