Radioactivity-Group Displacement Law_Chemistry

The nucleus that disintegrates is referred to as a parent nucleus, and the nucleus that remains after disintegration is referred to as a daughter nucleus.

Rutherford concluded in 1902 when investigating the influence of electric and magnetic fields on radiation that these radiations are made up of three different types of rays.

Alpha Rays

1. It is the same as helium atoms (He).
2. Electrical charge in units of +2e
3. The mass is four units.
4. Gase ionising power is high.
5. Because of the great mass, the kinetic energy is significant.
6. Fluorescence on ZnS is caused.

Beta Rays

1. It is the same as electrons
2. e units of electrical charge
3. The mass is equal to 1/1837 units.
4. Gase ionising power is modest.
5. The smaller mass makes the kinetic energy minimal, causing fluorescence on ZnS.

Gamma Rays

1. It is short-wavelength electromagnetic radiation.
2. There is no cost.
3. There is no mass.
4. The ionising power of gases is meagre, and the kinetic energy is zero due to the lack of mass.

According to group displacement law:

When a radioactive element emits α-particles from its nucleus, the atomic number of the new element or daughter element created is reduced by two units, and four units reduce the atomic weight. As a result, the new element’s position in the periodic table is shifted to the left by two groups.

The atomic number of the daughter element or new element increases when a radioactive element emits an α-particle. As a result, the new element’s position in the periodic table has been shifted one group to the right.

The daughter element is an isotope of the parent element if α-particle is released from the nucleus of a radioactive element, followed by two -particles in the following two transformations. The atomic number of the daughter and father are the same. As a result, the positions of the daughter and parent elements in the periodic table will stay unchanged according to Group displacement law.

History of Group Displacement Law

The revelation of radioactivity and subsequent research into radioactive materials resulted in the emergence of previously unknown compounds. From as early as 1902, Ernest Rutherford and Frederick Soddy argued that a chemical change of one component followed radioactive decay into another. Soddy and Kasimir Fajans separately unravelled the pattern of alterations that followed and radioactive decay around ten years later. They invented the notion of isotope (Soddy’s word) in the process, which enabled the categorisation of a large number of new constituents within the current structure of the periodic table.

Soddy merged the alpha and beta laws into the group displacement law in 1913: one alpha emission moves the periodic table two places back, while one beta emission moves it one position forward. As a result, a series of alpha-beta-beta emissions indicate a return to the table’s initial work.

Group Displacement Law – α-particle or β-particle

When an α – particle is lost, a new element with a lower atomic number and a lower mass number is produced, according to Soddy, Fajans, and Russell (1911-1913). When the β-particle is lost, a new element with an atomic number more significant than one is created. The parent element is the one that emits either α or β-particle, whereas the child element is the one that forms.

The results of group displacement law have been summarised as:

• The new element is created when an α – particle is expelled to the left of the parent element in the periodic table; this happens because the atomic number is decreased by 2.
• The new element is formed when a β-particle is emitted one position to the right of the parent element in the periodic table. This happens because the atomic number is increased by 1.
• The daughter element in the periodic table moves one group to the left of the parent element when a positron is emitted.

Calculating of number of α and β particles in a radioactive displacement transformation:

Parent element Daughter element  z1AM1  →  z2BM2

Number of α – particles =>  Change in mass number/4 = (M1-M2)/4

Number of β-particles = Let us assume ‘x’ β-particles and ‘y’ α – particles be emitted

Atomic number of parent element – 2y + x = Atomic number of daughter element

Z1 – 2y + x = Z2

Therefore, x = (Z2 – Z1 + 2y)

Group Displacement Law Example

The number of α-particle or β-particle released during the nuclear transition must be determined. It may be accomplished in the following manner:

a=b+4x or x=a-b
  —— equation i

C = d+2x-y —— equation ii

Where x = no. of a-emitted, y = no. of b-emitted

substituting the value of x from eq. I and eq. ii we get,

Conclusion

The chemistry of radioactive nuclei is known as nuclear chemistry. The group displacement law sufficiently determines the number of alpha and beta particles released.