Atoms & Nucleii

When an a-particle of mass m moving with velocity

v bombards on a heavy nucleus of charge Ze, its

distance of closest approach from the nucleus

depends on m as

• 1 / m²

• m

• 1 / m

• m²

An alpha nucleus of energy 1 / 2 mv² bombards a heavy nuclear target of charge Ze. Then the distance of closest approach for the alpha nucleus will be proportional to

• 1 / Ze

• v²

• 1 / m

• 1 / v⁴

In a Rutherford scattering experiment when a projectile of charge z₁ and mass M₁ approaches a target nucleus of charge z₂ and mass M₂, the distance of closest approach is r₀. The energy of the projectile is

• directly proportional to z₁z₂

• inversely proportional to z₁

• directly proportional to mass M₁

• directly proportional to M₁ × M₂

The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is

• 1

• 4

• 0.5

• 2

For which one of the following, Bohr model is not valid?

• Hydrogen atom

• Singly ionised helium atom (He⁺)

• Deuteron atom

• Singly ionised neon atom (Ne⁺)

The total energy of an electron in an atom in an orbit is – 3.4 eV. Its kinetic and potential energies are, respectively

• 3.4 eV, 3.4 eV

• – 3.4 eV, – 3.4 eV

• – 3.4 eV, – 6.8 eV

• 3.4 eV, – 6.8 eV

Consider 3rd orbit of He⁺ (Helium), using non-relativistic approach, the speed of electron in this orbit will be

• 0.73 × 10⁶ m/s

• 3.0 × 10⁸ m/s

• 2.92 × 10⁶ m/s

• 1.46 × 10⁶ m/s

The energy of a hydrogen atom in the ground state is –13.6 eV. The energy of a He+ ion in the first excited state will be

• –13.6 eV

• –27.2 eV

• –54.4 eV

• –6.8 eV

In which of the following systems will the radius of the first orbit (n = 1) be minimum?

• doubly ionized lithium

• singly ionized helium

• deuterium atom

• hydrogen atom

When hydrogen atom is in its first excited level, its radius is .......... of the Bohr radius.

• twice

• 4 times

• same

• half