Structure of Atom

Question 1

What is radiation

Answer 1

A mode of transference of energy

Question 2

What is wavenumber

Answer 2

It is the number of waves per metre. (1/wavelength )

Question 3

What is the electromagnetic spectrum

Answer 3

The arrangement of different types of electromagnetic radiations in decreasing order of their wavelengths

Question 4

State the order of the electromagnetic spectrum

Answer 4

radio>micro>infra>visible>UV>X>gamma>cosmic

Question 5

Why couldnt E.W.T explain black body radiation

Answer 5

Because according to it, only one colour should have been emitted irrespective of temperature

Question 6

What is photoelectric effect

Answer 6

The ejection of electrons when a radiation of threshold frequency falls on the surface on the metal

Question 7

State the postulates of Plank’s Quantum theory

Answer 7

1. Energy is absorbed or emitted discontinuously in small packets
2. Each packet of energy is a quantum and the quantum of light is a photon
3. Energy of photon = hv
4. A body can absorb or emit only a whole number multiple of one photon

Question 8

What is emission spectra

Answer 8

It is the spectrum obtained when radiations emitted by the excited substance are analyzed by a spectroscope. It has bright lines separated by dark spaces

Question 9

What is absorption spectrum

Answer 9

The spectrum is obtained when white light is passed through a substance in a gaseous or solution state. It consists of a band of colours with dark lines

Question 10

Name the scientists which study the different parts of the line spectrum

Answer 10

UV - Lyman - n1
Visible - Balmer - n2
Infrared - Paschen - n3
Infrared - Brackett - n4
Infrared - Pfund - n5

Question 11

How to calculate the wavelength for hydrogen spectrum

Answer 11

(1/Wavelenght) = 109678(1/n1^2 - 1/n2^2) where n1 is the final shell

Question 12

What is the energy of a shell

Answer 12

(-2 * π^2 * Z^2 * e^4 * m)/ (n^2 * h^2)

Question 13

What is Bohr’s model of atom

Answer 13

1. Electrons move in fixed non-radiating orbits called stationary states
2. Each stationary state has a fixed energy so it is known as energy levels
3. Only shells with angular momentum (mvr) which is a whole no. multiple oh h/2pi is permitted
4. Energy is quantized
5. electrons have a normal state with doesn’t lose energy

Question 14

How to calulate number of lines in spectru

Answer 14

n(n-1)/2 where n is the outermost shell

Question 15

What is Heisenberg theory

Answer 15

It is impossible to know the exact position and momentum of a subatomic particle at the same time

Question 16

What does De Broglie state

Answer 16

That all materials posses in motion posses wave nature
wavelength = h / mv

Question 17

The mathematical statement of Heisenberg uncertainty principle

Answer 17

Δx . Δp =>= h/4π

Question 18

What are quantum numbers

Answer 18

They are the index numbers which are used to specify the position and energy of an electron in the atom

Question 19

What are the four quantum number

Answer 19

Principal (n) - energy level
Azimuthal (l) - subshell
Magnetic (m) - orientation of orbital
Spin (s) = +1/2, -1/2

Question 20

How to calculate the total number of electrons in a subshell

Answer 20

2(2l+1)

Question 21

What is the maximum number of orbitals in a shell

Answer 21

n^2

Question 22

What does Pauli’s exclusion principle state

Answer 22

No two electrons in an orbital of an atom can have the same 4 quantum numbers ( no two electrons with same spin can fill an orbital)

Question 23

How many nodes does s orbital have

Answer 23

(n-1) when n is the energy level

Question 24

How many nodes does p orbital have

Answer 24

(n-2)

Question 25

What are degenerate orbitals

Answer 25

Orbitals having the same energy