Taking the Bohr radius as a₀ = 53pm, the radius of Li⁺⁺ ion its ground state, on the basis of Boh''s model, will be about

1

(a)

53pm

(b)

27pm

(c)

18pm

(d)

13pm

The simple Bohr model cannot be directly applied to calculate the energy levels of an atom with electrons. This because

1

(a)

of the electrons not being subjects to a central force

(b)

of the electrons colliding with each other

(c)

of screening effects

(d)

the force between the nucleus and an electron will no longer be given by Coulomb's law

For the ground state, the electron in the H-atom has an angular momentum =h, according to the simple Bohr model. Angular momentum is a vector and hence there will be infinitely many orbits with the vector pointing in all possible directions. In actuality, this is not true,

1

(a)

because only one of these would have a minimum energy

(b)

because only one of these would have a minimum energy

(c)

angular momentum must be in the direction of spin of electron

(d)

because electrons go arround only in horizontal obits.

Two H atoms in the ground state collide inelastically kinetic energy is reduced is

1

(a)

10.20 eV

(b)

20.40 eV

(c)

13.6 eV

(d)

27.2 eV

A set of atoms in an excited state decays 

1

(a)

in general to any of the states with lower energy

(b)

into a lower state only when excited by an external electric field

(c)

all together simultaneously into a lower state

(d)

to emit protons only when they collide.