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MHT-CET : Chemistry Entrance Exam

MHT - CET : Chemistry - Nuclear and Radiochemistry Page 2

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13.

Soddy's group displacement law

 

i. When an element emits a-particle,

ii. When an element emits b-particle,

iii. During
g-emission, A and Z remain the same.

 

14.

Disintegration law

 

The number of atoms disintegrated per unit time is a constant fraction of the total number of the atoms present at that instant.

 

15.

Decay or disintegration constant (l)

 

The fraction of the total number of atoms (nuclei) undergoing radioactive disintegration per unit time is called decay or disintegration constant of the element.

 

l

- d N/N

dt

 

Or   l

2.303

 log

(

N0

),

t

Nt

 

where 

N0 = total number of radioactive atoms initially present (t = 0).

 

Nt = total number of radioactive atoms present at time t.

 

 

16.

Half-life period (t1/2)

 

The time required for the disintegration of a radioactive element to reduce to half of the original amount is called half-life period.

 

t1/2 = 

0.693

l

 

17.

Artificial transmutation

 

The process of conversion of a stable isotope of one element into a stable isotope of another element by bombarding it with suitable high energy (nuclear) particles is called artificial transmutation.

 

 

18.

Target

 

The atomic nucleus which is bombarded by high energy nuclear particles (projectiles) is called a target.

 

19.

Projectile

 

The high energy nuclear particles such as a-particle, proton or neutron, which are used to bombard an isotope of an element are called projectiles.

 

20.

Product or recoil nucleus

 

The new atom produced from the target nucleus after it is bombarded with projectiles and which has a mass number not far different from that of target, is known as product or recoil nucleus.

 

21.

Emissions

 

The particles which are ejected from the target nucleus after bombardment with projectiles are called emissions.

 

22.

Natural radioactivity

 

The spontaneous emission of radiation from the nuclei of heavy elements is called natural radioactivity.

 

23.

Artificial radioactivity

 

The phenomenon of conversion of a stable nucleus (non-radioactive) into an unstable radioactive nucleus by artificial disintegration is called artificial radioactivity.

 



 

24.

Examples of artificial transmutation of elements using various projectiles

 

A) Using a-particles

(i)

(ii)

 

B) Using deuterium nuclei



 

C) Using protons

(i)

(ii)

 

D) Using neutrons

(i)

(ii)

 

25.

Types of nuclear reactions

 

  1. Natural radioactivity
  2. Artificial transmutation
  3. Artificial radioactivity
  4. Nuclear fission
  5. Nuclear fusion

 

26.

Radioisotopes

 

The naturally unstable elements which spontaneously emit some radiations like a-particles, protons, neutrons, g-rays, etc. are called as radioisotopes.
Radio isotope dating was developed by W. F. Libby.

 

27.

Uses of radioisotopes

A]

Carbon dating

i)

Using 

14

 C

 isotope of carbon (a beta emitter), the age of archaeological materials containing

6

matter of living origin can be found.

 

 

B]

Medicines

i)

24

 Na 

(in the form of NaCl) to study blood circulation.

11

 

 

ii)

131

 I 

to diagnose and treat thyroidal disorders.

53

 

 

iii)

32

 P 

to treat leukaemia.

15

 

 

iv)

60

 Co 

to treat certain types of cancers.

27

 

 

v)

60

 Ni 

to stop the growth of cancer.

28

 

 

C]

Agriculture

i)

32

 P 

to study plant metabolism and to syudy the usefulness of phosphorus fertilisers.

15

 

 

ii)

14

 C 

to study photosynthesis in plants.

6

 

 

iii)

40

 Ca 

to find out the uptake of calcium by the plants from the soil.

20

 

 

D]

Production of synthetic elements

i)

ii)

 

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