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Alpha decay is a fascinating process that occurs at the heart of unstable atoms as they strive for stability. Imagine a helium nucleus, a tiny particle made up of two protons and two neutrons, being ejected from an atom's nucleus. This event signifies alpha decay, which results in the reduction of the atomic number by two and the mass number by four.

Let's take an example to illustrate this: suppose we have an atom of uranium-238. This heavy atom wants to shed some weight to become more stable, so it undergoes alpha decay and ejects an alpha particle to transform into thorium-234.

The alpha particles are relatively heavy and carry a double positive charge due to the two protons. Once emitted, alpha particles can be easily stopped by something as thin as a sheet of paper or even the outer layer of human skin. However, if inhaled or ingested, they can be a health hazard due to their high ionizing power.

Beta decay represents a different pathway to stability taken by unstable nuclei. It can go one of two ways: either a neutron is too shy and decides to dress up as a proton, ejecting an electron in the process—this is beta minus decay; or a proton feels like it's one too many and morphs into a neutron, releasing a positron—this is beta plus decay.

In beta minus decay, an atom gains a proton while in beta plus decay, it loses one. Both these processes aim to balance the ledger of protons and neutrons to reach a stable configuration. Unlike alpha particles, beta particles—electrons or positrons—have much smaller mass and can penetrate deeper into materials, making them both interesting and potentially dangerous.

To visualize these processes, consider carbon-14, which undergoes beta minus decay to become stable nitrogen-14. On the flip side, nitrogen-13 may undergo beta plus decay to achieve stability in the form of carbon-13.

Gamma decay is the nucleus' way of letting off steam. When a nucleus feels excited—packed with too much energy—it can relax by emitting a gamma ray, a form of pure energy without mass or charge.

Gamma rays are like the X-rays at a doctor's office, or the UV light that gives you a sun tan; they're all part of the electromagnetic spectrum, but gamma rays are even more powerful. These energetic photons can zoom through most materials, requiring heavy lead or concrete to block them effectively. Despite being daunting because of their penetrative power, gamma rays are used beneficially in medicine for imaging and cancer treatment.

Consider a nucleus that has just done the hard work of alpha or beta decay. Often, it's like after a good workout—still buzzing with energy. It then uses gamma decay to cool down to its new, more relaxed and stable state without changing its identity in terms of protons or neutrons.