Pick out the wrong statement.

• Atoms with same number of nucleons but different number of protons are called isobars.
• Atoms with same number of protons but different number of nucleons are called isoters.
• Out of α, β, and γ-rays, the one having maximum penetration power are γ-rays.
• The product formed by emission of α-particle has mass number less by 4 units than the parent nuclide.