Atoms

In the first excited state of hydrogen atom, the energy of its electron is −3.4 eV. The radial distance of the electron from the hydrogen nucleus in this case is approximately : (Take 1 eV = 1.6 10-19 J, e = 1.6 10-19 C and 14 0 = 9 109 N m2/C2)

1. 2.1 10-8 m
2. 2.1 10-10 m
3. 2.1 10-11 m
4. 2.1 10-9 m

Consider that an electron is revolving in an excited state of Hydrogen atom with velocity 25.6 105 ms-1. The radius of the orbit is x 10-9 m. The value of x is: [Take the mass of electron to be 9 10-31 kg, charge of electron = -1.6 10-19 C and 14 0 = 9 109 Nm2C-2]

1. 1
2. 4
3. 3
4. 2

A particle of mass m is moving around the origin with a constant force F pulling it towards the origin. If Bohr model is used to describe its motion, the radius of the nth orbit and the particle's speed v in the orbit depend on n as

1. r n2/3; v n1/3
2. r n4/3; v n-1/3
3. r n1/3; v n1/3
4. r n1/3; v n2/3

De-Broglie wavelength of an electron orbiting in the n = 2 state of hydrogen atom is close to (Given Bohr radius = 0.052 nm)

1. 1.67 nm
2. 2.67 nm
3. 0.067 nm
4. 0.67 nm

The radius of inner most orbit of hydrogen atom is 5.3 10-11 m. What is the radius of third allowed orbit of hydrogen atom?

1. 1.06 Å
2. 1.59 Å
3. 4.77 Å
4. 0.53 Å

Let T1 and T2 be the energy of an electron in the first and second excited states of hydrogen atoms, respectively. According to the Bohr's model of an atom, the ratio T1 : T2 is

1. 1 : 4
2. 4 : 1
3. 4 : 9
4. 9 : 4

Let R1 be the radius of the second stationary orbit and R2 be the radius of the fourth stationary orbit of an electron in Bohr's model. The ratio R1R2 is :

1. 4
2. 0.25
3. 0.5
4. 2

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

1. Singly ionised helium atom (He+)
2. Deuteron atom
3. Singly ionised neon atom (Ne+)
4. Hydrogen atom

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

1. 3.4 eV, -6.8 eV
2. 3.4 eV, 3.4 eV
3. -3.4 eV, -3.4 eV
4. -3.4 eV, -6.8 eV

The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is

1. 1 : 1
2. 1 : -1
3. 2 : -1
4. 1 : -2

Consider 3rd orbit of He+ (Helium), using non-relativistic approach, the speed of electron in this orbit will be [given K = 9 109 constant, Z = 2 and h (Planck's Constant) = 6.6 10-34 J s]

1. 0.73 106 m/s
2. 3.0 108 m/s
3. 2.92 106 m/s
4. 1.46 106 m/s

An electron in hydrogen atom makes a transition n1 n2 where n1 and n2 are principal quantum numbers of the two states. Assuming Bohr's model to be valid, the time period of the electron in the initial state is eight times that in the final state. The possible values of n1 and n2 are

1. n1 = 6 and n2 = 2
2. n1 = 8 and n2 = 1
3. n1 = 8 and n2 = 2
4. n1 = 4 and n2 = 2

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

1. -13.6 eV
2. -27.2 eV
3. -54.4 eV
4. -6.8 eV

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

1. -13.6 eV
2. -27.2 eV
3. -54.4 eV
4. -6.8 eV

The ground state energy of hydrogen atom is -13.6 eV. When its electron is in the first excited state, its excitation energy is

1. 10.2 eV
2. 0
3. 3.4 eV
4. 6.8 eV

The total energy of electron in the ground state of hydrogen atom is -13.6 eV. The kinetic energy of an electron in the first excited state is

1. 6.8 eV
2. 13.6 eV
3. 1.7 eV
4. 3.4 eV

The total energy of an electron in the first excited state of hydrogen atom is about -3.4 eV. Its kinetic energy in this state is

1. 3.4 eV
2. 6.8 eV
3. -3.4 eV
4. -6.8 eV

The Bohr model of atoms

1. Assumes that the angular momentum of electrons is quantized.
2. Uses Einstein's photoelectric equation.
3. Predicts continuous emission spectra for atoms.
4. Predicts the same emission spectra for all types of atoms.

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

1. doubly ionized lithium
2. singly ionized helium
3. deuterium atom
4. hydrogen atom

The energy of hydrogen atom in nth orbit is En, then the energy in nth orbit of singly ionised helium atom will be

1. 4En
2. En/4
3. 2En
4. En/2