Which of the following notations represents an alpha particle? A. 2 He
C. B+
В. В
D. Y

A. 2 He

Explanation:

The notation of an alpha particle is depicted as:

                     ₂He

An alpha particles is a nucleus of 2 protons and 2 neutrons. So it is actually a Helium cation.

Alpha particles are monoenergetic and they mostly have discrete energy.

So, the mass number of the particle is 4 and atomic number is 2

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.