Question

Q.no 2. Which isotopes of elements are radioactive
A: Atomic number above 83
B: Atomic number above 92
C: Atomic number above 56
D: All elements in the periodic table​

Answer 1

Answer: (A) All elements with atomic numbers greater than 83 are radio isotope meaning that these elements have unstable nuclei and are radioactive.

Explanation:

Hope it helps

and mark me as brainlist answer

Thank you : )

Answer 2

Answer:

The isotopes of elements are radioactive with the atomic numbers above $83$.

Therefore, option A) Atomic number above $83$, is correct.

Explanation:

Isotopes:

• Isotopes are two or more atoms that have the same number of protons but have a different number of neutrons.

Radioactive elements:

• They are made up of elements whose nuclei are unstable.

Now,

The atomic number of the elements greater than $83$ are radioactive because;

• The atoms are not stable because of the level of nuclear binding energy.

• The stability of the atoms of the different elements is dependent on their nuclear binding energy.
• If the nuclear binding energy of an atom is more than the repulsive forces between the nucleons, then it is considered stable.
• But, if the nuclear binding energy of an atom is less than the repulsive forces between the nucleons, then it is considered unstable.

Therefore, because of the more repulsive force between the nucleons of the atoms, the elements become unstable.

Thus, the isotopes of elements are radioactive.

Hence, the isotopes of elements are radioactive with the atomic numbers above $83$.