431.

For the Paschen series the values of n₁ and n₂ in the expression $∆\mathrm{E} =\mathrm{Rhc}\left(\frac{1}{{\mathrm{n}}_1^2}-\frac{1}{{\mathrm{n}}_2^2}\right) \mathrm{are}$

• n₁= 1, n₂ = 2, 3, 4, ...

• n₁= 2, n₂ = 3, 4, 5,...

• n₁= 3, n₂ = 4,5,6,...

• n₁= 4, n₂ = 5,6,7,...

In Sommerfeld's modification of Bohr's theory, the trajectory of an electron in a hydrogen atom is

• a perfect ellipse

• a closed ellipse-like curve, narrower at the perihelion position and flatter at the aphelion position

• a closed loop on spherical surface

• a rosette

If a species has 16 protons, 18 electrons and 16 neutrons, find the species and its charge.

• S^1-

• Si^2-

• P^3-

• S^2-

Which of the following expressions gives the de-Broglie relationship?

• $\mathrm{p}=\frac{\mathrm{h}}{\mathrm{mv}}$

• $\mathrm{\lambda }=\frac{\mathrm{h}}{\mathrm{mv}}$

• $\mathrm{\lambda }=\frac{\mathrm{h}}{\mathrm{mp}}$

• $\mathrm{\lambda m}=\frac{\mathrm{v}}{\mathrm{p}}$

The orbital angular momentum of an electron in 2s orbital is

• $+\frac{1}{2}\frac{\mathrm{h}}{2\mathrm{\pi }}$

• zero

• $\frac{\mathrm{h}}{2\mathrm{\pi }}$

• $\sqrt{2}\frac{\mathrm{h}}{2\mathrm{\pi }}$

The number of electron and neturons of an element is 18 and 20 respectively. Its mass number is

• 2

• 17

• 37

• 38

$\mathrm{The} \mathrm{number} \mathrm{of} \mathrm{\alpha } \mathrm{and} \mathrm{\beta } \mathrm{particles} \mathrm{emitted} \mathrm{in} \mathrm{nuclear} \mathrm{reaction} {}_{90}\mathrm{Th}^{228}\to {}_{83}\mathrm{Bi}^{212}$ are respectively

• 4,1

• 3,7

• 8,1

• 4,7

The radius of hydrogen atom is 0.53 Å. The radius of ₃Li²⁺ is of:

• 1.27 Å

• 0.17 Å

• 0.57 Å

• 0.99 Å

Wave nature of electrons was demonstrated by :

• Schrodinger

• de-Broglie

• Davisson and Garmer

• Heisenberg

4d, 5p, 5f and 6p orbitals are arranged in the order of decreasing energy. The correct option is:

• 6p > 5f > 5p > 4d

• 6p > 5f > 4d > 5p

• 5f > 6p > 4d > 5p

• 5f > 6p > 5p > 4d