alpha partical is a He nucleus. When decaying alpha particle mass is reduced by 4 and atomic number is reduced by 2.
The actual element which has 102 protons is No (Nobelium).
Since it has 167 neutrons, the mass = protons + neutrons = 102 + 167 = 269
after an alpha decay, the new element formed has 100 protons which is Fm ( Fermium)
the alpha decaying equation is,
₁₀₂²⁶⁹No → ₁₀₀²⁶⁵Fm + ₂⁴α + heat
the total mass and the atomic number( numbe rof protons) must be equal in both sides.
