atomic structure

Question 1

what are subatomic particles

Answer 1

A large number of subatomic particles have been discovered but among them only
electron, proton and neutron are of great importance and hence, these three are called
fundamental particles

Question 2

discovery of electron

Answer 2

. Cathode rays were a stream of
fast moving negatively charged particles, called electrons.
The specific charge is the
ratio of charge to mass of an electron, i.e. e/m ratio of electron was found to be
same for all gases.
. Its value is=1.7x10^11 c/kg
mass of electron=9.1x10^-31
 charge on electron=1.6x10^-27

Question 3

discovery of proton

Answer 3

These rays consist of positively
charged particles, called protons
Unlike cathode rays, their e/m value depends upon
the nature of gas taken in the tube. The e/m value is maximum for hydrogen gas.

Question 4

neutron

Answer 4

These are the heaviest
particles of the atom.
mass of neutron =1.6x10^-27 kg
charge on neutron=0

Question 5

Different Types of Atomic Species

Answer 5

1. Isotopes Isotopes are the species with same atomic number but different mass
   numbers.
   2.Isobars Isobars are the species with same mass number but different atomic
   numbers
   3.Isotones Isotones are the species having same number of neutrons.
   4.Isodiaphers Isodiaphers are the species with same
   isotopic number

Question 6

isotopic number

Answer 6

Isotopic number = mass number − 2 × atomic number

Question 7

Thompson model of atom

Answer 7

Thomson model of an atom proposed that an atom is a sphere
of positive charges uniformly distributed, with the electrons
scattered as points throughout the sphere. This was also
known as plum pudding model.

Question 8

limitation of Thompson model of atom

Answer 8

Thomson’s model was able to explain the overall neutrality of
the atom, but it could not satisfactorily explain the results of
scattering

Question 9

Rutherford model of atom

Answer 9

Rutherford bombarded a thin foil of gold with high speed
positively chargedα-particles and made the following
observations and conclusions :
● Most of theα-particles passed through the foil undeflected, it
means that most of the space in atom is empty.
● Some of them were deflected, but only at small angles. This
shows that there is something positively charged at the centre.
● A very few α-particles were deflected by nearly 180°, it
means that the positively charged solid thing (called
nucleus) is very small.
● The electrons present in empty space, around the nucleus,
revolve around with a very high speed.m

Question 10

limitation of bohrs model

Answer 10

Rutherford’s model cannot explain the stability of an atom.
When a charge is subjected to acceleration around an
opposite charge, it emits radiation continuously

Question 11

electromagnetic spectrum

Answer 11

comic rays< x-rays < ultraviolet< visible spectrum

Question 12

measurements

Answer 12

1pm=10^-12=m 
1Å=10^-10m 
1nm=10^-9m
1μm=10^-6m
1mm=10^-3m
1cm=10^-2m

Question 13

frequency

Answer 13

no of waves passed from a particular spot in 1 second
v=1/t, c=speed of light
c=λx1/t=c=λxV, 
  v=c/λ
v=c x wave number

Question 14

wave number

Answer 14

no of waves present in 1cm
wave number=1/λ
=v/c

Question 15

planks theory

Answer 15

E=hv
h=6.626 x 10^-34 j.sec 
h=E/v
E=nhv
n=no. of quanta

Question 16

photo electric effect

Answer 16

v= √(2hc/m)(1/λ-1/λo)

λo=max wavelength

Question 17

work function

Answer 17

=hc/λo
=hVo
Vo=c/λo

Question 18

dual nature of matter

Answer 18

λ=h/mc
λ=de-broglie wavelength 
λ=H/MV
λ=h/p
p=momentum

Question 19

relation between KE and de-broglie wavelength

Answer 19

λ=h/ √2KExM

Question 20

line spectrum of hydrogen

Answer 20

no of emmision lines=n(n-1)/2
wave no.=1/ λ=Rh(1/n^2-1/n^2)z^2
rydberg const=109677
=1.09 x 10^5

Question 21

energy of electron in nth energy level

Answer 21

Enth= -2.18x10^-18z^2/n^2 J/ATOM

Question 22

radius of an energy level

Answer 22

Rn=52.9n^2/Z pm

Question 23

velocity of a moving electron is different energy level

Answer 23

Vnth=2.16x10^6z/n m/sec

Question 24

angluar momentum of a electron

Answer 24

mvr=nh/2π