681.

Based on equation $\mathrm{E} = -2.178 \times {10}^{-18} \mathrm{J} \left(\frac{{\mathrm{Z}}^2}{{\mathrm{n}}^2}\right)$ certain conclusions are written. Which of them is not correct?

• The negative sign in equation simply means that the energy of electron bound to the nucleus is lower than it would be if the electrons were at the infinite distance from the nucleus.

• Larger the value of n, the larger is the orbit radius

• Equation can be used to calculate the change in energy when the electron changes orbit.

• For n = 1 the electron has a more negative energy than it does for n = 6 which means that the electron is more loosely bound in the smallest allowed orbit.

The energy of an electron in first Bohr orbit of H-atom is-13.6 eV. The possible energy value of electron in the excited state of Li²⁺ is:

• - 122.4 eV

• 30.6 eV

• - 30.6 eV

• 13.6 eV

The representation of the ground state electronic configuration of He by box-diagram as 

$\uparrow \uparrow$

is wrong because it violates:

• Heisenberg's uncertainty principle

• Bohr's quantization theory of angular momenta

• Pauli exclusion principle

• Hund's rule

The electronic transitions from n = 2 to n = 1 will produce shortest wavelength in (where n = principal quantum state)

• Li²⁺

• He⁺

• H

• H⁺

A radioactive atom ${}_{\mathrm{Y}}{}^{\mathrm{X}}\mathrm{M}$ emits two $\mathrm{\alpha }$ particles and one $\mathrm{\beta }$ particle successively. The number of neutrons in the nucleus of the product will be:

• X - 4 - Y

• X - Y - 5

• X - Y - 3

• X - Y - 6

1 mole of photon, each of frequency 2500 s^-1, would have approximately a total energy of

• 10 erg

• 1 J

• 1 eV

• 1 MeV

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?

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

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

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

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