Question

State the relation between atomic number and atomic mass light elements. state which elements are considered​ radioactive giving reason

Answer 1

Difference between atomic mass and atomic number-

Atomic number(Z)- It is the number of protons or number of electrons present in an element.

Atomic mass(A)- It is the sum of protons and neutrons(called nucleons) present in the nucleus of an element or atom. It is also called atomic weight.

Certain atoms found in the nature are unstable due to unbalanced forces(either excess of protons or neutrons in the nucleus)i.e the nucleus has an excess of internal energy. Such atoms tend to be radioactive.

Elements having atomic number greater than 92( transuranic elements) are considered to be radioactive.

Reason-

unstability of nuclei

Electomagnetic force of repulsion

Binding energy

Radioactive elements release subatomic particles or energy as decay.

Answer 2

in light elements the atomic mass is is nearly double than that of the atomic number.

if the neutron by proton ratio of elements is is greater than 1.5 then it is considered to be an unstable radioactive element or heavy element