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Alpha decay is a type of radioactive decay where an unstable atom releases an alpha particle. An alpha particle is composed of 2 protons and 2 neutrons, identical to a helium nucleus. When alpha decay occurs, the parent atom loses 4 units from its mass number and 2 units from its atomic number. This results in the formation of a new element.

For example, consider the alpha decay of plutonium-239, or \( ^{239}_{94} \text{Pu} \). During this process, the plutonium nucleus emits an alpha particle, leading to a reduction of its atomic number from 94 to 92 and its mass number from 239 to 235. Thus, the resulting daughter nucleus is uranium-235, or \( ^{235}_{92} \text{U} \).

Key points to remember:

• Alpha particles are heavy and positively charged.
• Alpha decay reduces atomic number by 2 and mass number by 4.
• It is commonly seen in heavy elements like uranium and radium.

In beta-minus (\(\beta^-\)) decay, a neutron is transformed into a proton within the nucleus, accompanied by the emission of an electron and an antineutrino. The transformation increases the atomic number by 1, but interestingly, the mass number remains the same. This is because the neutron and proton are similar in mass.

Applying this to sodium-24, or \( ^{24}_{11} \text{Na} \), a neutron within the sodium nucleus converts to a proton, which increases the atomic number by 1 from 11 to 12. Therefore, sodium transforms into magnesium-24, \( ^{24}_{12} \text{Mg} \).

What to note about beta-minus decay:

• It increases the atomic number by 1.
• The mass number remains unchanged.
• It is a common decay mode in neutron-rich nuclei.

Beta-plus (\(\beta^+\)) decay involves the conversion of a proton into a neutron, a positron (the antimatter equivalent of an electron), and a neutrino. Similar to beta-minus decay, the mass number remains unchanged. However, since a proton is converted to a neutron, the atomic number decreases by 1.

An example is the decay of oxygen-15, expressed as \(^{15}_{8}\text{O} \). In this decay, the atomic number is reduced from 8 to 7 as a proton in the oxygen nucleus transforms into a neutron, creating nitrogen-15, \(^{15}_{7}\text{N} \). The mass number, however, holds steady at 15.

Highlights of beta-plus decay include:

• The atomic number decreases by 1.
• The positron is emitted along with a neutrino.
• This decay type is typical in proton-rich nuclides.