When first discovered α, β and γ radioactivity were referred to as α−rays, β-rays and γ- rays. Now we refer to α-particles and β-particles, but still use the term γ-rays. What type of particles are α and β commonly known as? What type of ray is γ commonly known as? What are the signs of the charges on the three forms of radiation?

An [tex]\alpha[/tex] particle consists of 2 protons and 2 neutrons: therefore, in an alpha-decay, the nucleus loses 2 units of atomic number (number of protons) and 2 units of mass number (sum of protons+neutrons).

The alpha-particle consists of 2 protons of 2 neutrons: so it corresponds to a nucleus of helium, which consists exactly of 2 protons and 2 neutrons.

- There are two types of [tex]\beta[/tex] decay:

-- In the [tex]\beta^-[/tex] decay, a neutron decays into a proton emitting a fast-moving electron and an anti-neutrino:

[tex]n \rightarrow p + e^- + \bar{\nu}[/tex]

and the [tex]\beta[/tex] particle in this case is the electron

-- In the [tex]\beta^+[/tex] decay, a proton decays into a neutron, emitting a fast-moving positron and a neutrino:

[tex]p \rightarrow n + e^+ + \nu[/tex]

and the [tex]\beta[/tex] particle in this case is the positron.

2) Gamma ray

A [tex]\gamma[/tex] decay occurs when an unstable (excited state) nucleus decays into a more stable state. In this case, there are no changes in the structure of the nucleus, but energy is released in the form of a photon:

[tex]X^* \rightarrow X + \gamma[/tex]

where the wavelength of this photon usually falls in the part of the electromagnetic spectrum corresponding to the gamma ray region.

So, the [tex]\gamma[/tex] ray is commonly known as gamma radiation.

3)

The sign of the three forms of radiation are the following:

- [tex]\alpha[/tex] particle: it consists of 2 protons (each of them carrying a positive charge of +e) and 2 neutrons (uncharged), so the total charge is

Q = +e +e = +2e

- [tex]\beta[/tex] particle: in case of [tex]\beta^-[/tex] radiation, the particle is an electron, so it carries a charge of

Q = -e

in case of [tex]\beta^+[/tex] radiation, the particle is a positron, so it carries a charge of

Q = +e

- [tex]\gamma[/tex] radiation: the [tex]\gamma[/tex] radiation consists of a photon, and the photon has no charge, so the charge in this case is

Q = 0