Atoms And Its Structure

Question 1

What is the absolute charge of proton?

Answer 1

+ 1.6022 × 10^-19

Question 2

Explain Rutherford nuclear model of atom?

Answer 2

• All the positive charge and most of the mass of an atom are concentrated in an extremely small region called nucleus.
• Electrons revolve around the nucleus in a fixed path called orbit.
• Electrons and neutrons are held together by electrostatic force of attraction.

Question 3

Absolute charge of Electron.

Answer 3

-1.6022 × 10^-19

Question 4

Explain Rutherford alpha ray scattering experiment.

Answer 4

Observation
a) Most of the alpha particles passed through the foil without any deflection.
b) Few particles passed through the gold foil with a small angle.
c) Very few alpha particles deflected through the gold foil with very large angle.

Conclusion
a) Most part of an atom is empty.
b) Atom consist of a positive centre (nucleus).
c) Nucleus of an atom occupies very small space.

Question 5

Mass of proton

Answer 5

1.6×10^-27

Question 6

Limitation or drawbacks of Rutherford atomic model.

Answer 6

a) It couldn’t explain the stability of atom.
b) It couldn’t explain the structure of atom.

Question 7

What is an isotope? Examples?

Answer 7

Same atomic number and different mass number.
Eg:- Protium and Tritium (radioactive isotope of hydrogen)

Question 8

Mass of electron

Answer 8

9.01×10^-31

Question 9

What is a frequency? How it is represented? What is it’s SI unit?

Answer 9

Frequency is the no. of wavelengths passed through a point at one second. It is represented by neu (v).
It’s SI unit is hertz (Hz).

Question 10

What is Isobars?

Answer 10

Atoms with same number and different mass number.
Eg:- 6C^14 , 7N^14

Question 11

Planck’s Quantum Theory.

Answer 11

a) Atoms absorb energy not in a continuous manner but discontinuously in small packets of energy are called quantums.
b) The energy of quantum radiation is proportional to its frequency.

E= hc/ λ

Question 12

Who discovered Photoelectric effect?

Answer 12

H. Hertz

Question 13

What is planck’s constant?

Answer 13

6.626×10^-34

Question 14

Photoelectric effect?

Answer 14

The phenomenon of ejection of electron by metals like alkaline and alkaline earth metals when light of suitable frequency falls on them.

Question 15

Threshold energy?

Answer 15

Minimum frequency to undergo Photoelectric effect when light falls on them.

Question 16

What are the characteristics of Photoelectric effect?

Answer 16

• The no. of electrons ejected is proportional to the intensity of light.

• The kinetic energy of atom is directly proportional to the frequency of incident light.

Question 17

Equation of Photoelectric effect?

Answer 17

1/2mv^2 = h(v - v°)

Question 18

Explain different spectrum lines present in line spectrum of hydrogen atom?

Answer 18

Lyman, Balmer, Paschen, Brackett, Pfund.

Question 19

De broglies equation?

Answer 19

λ = h/mc or λ = h/p where p is momentum