What is the change in atomic mass number when an atom emits an alpha particle?

When an atom emits an alpha particle, its atomic number will be reduced by two, and its mass number will be reduced by four since atomic number is the number of protons.

An alpha particle is essentially a helium nucleus composed of two protons and neutrons.

petroleum? coal maybe?

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be