What is the change in atomic mass number when an atom emits an alpha particle?
a.
decreases by 2
c.
increases by 2
b.
decreases by 4
d.
increases by 4

Decreases by 4

Explanation:

An alpha particle is made of two protons and two neutrons. An alpha decay involves the ejection of an alpha particle from the nucleus. Therefore since an alpha particles is equivalent to a helium nucleus, it involves the loss of 2 protons and 2 neutrons. Hence, we can conclude that when a nucleus emits an alpha particle, the mass number or the atomic mass decreases by 4 and the atomic number decreases by 2.

Ibelieve your answer is b.hope this : )

An  atom  (ours, not carroll's) consists of a positively charged  nucleus, surrounded by one or more negatively charged particles called  electrons. the positive charges equal the negative charges, so the atom has no overall charge; it is electrically neutral. most of an atom's mass is in its nucleus; the mass of an electron is only 1/1836 the mass of the lightest nucleus, that of hydrogen. although the nucleus is heavy, it is quite small compared with the overall size of an atom. the radius of a typical atom is around 0.1 to 0.25 nanometres (nm), whereas the radius of a nucleus is about 10-6  nm.  *  if an atom were enlarged to the size of the earth, its nucleus would be only 200 feet in diameter and could easily rest inside a small football stadium.read more on -