Decay and rays

Alpha decay: the nucleus spits out an alpha particle which is just a helium nucleus (2 protons + 2 electrons)

Mass number (top) : drops by 4

Atomic number (bottom): drops by 2

Remember: it loses a big chunk so the element will drop back 2 spots on the periodic table


Beta decay: the nucleus has too many neutrons. A neutron converts into a proton and ejects a high speed electron (the beta particle)

Mass number (top): no change

Atomic number (bottom): increases by 1 (gained an extra proton)

Remember: mass stays identical, but the element moves up 1 spot on the periodic table Parent



Damage to the body:


Alpha particles: extremely low

  • External biological damage: Negligible to none.

  • An alpha particle carries a +2 charge, and because it is so bulky it almost instantly collides with air molecules or matter. From an external source, it cannot penetrate the dead layer of cells on the surface of our skin

  • While harmless outside the body, alpha emitters are the most dangerous if inhaled or ingested, because inside living tissue their high mass and charge rip through DNA directly.


Beta particles: Moderate

  • External biological damage: Skin burns and superficial tissue damage ("beta burns").

  • Beta particles are high-speed electrons. Being much smaller and carrying a single -1 charge, they can penetrate past the dead skin layer into the living germinal layer of the epidermis (a few millimeters to roughly a centimeter into tissue).

  • They ionize molecules in living skin cells, breaking chemical bonds and causing acute localized burns, redness, and long-term risk of skin cancers or cataracts if exposed to the eyes. They can be stopped by a thin sheet of plastic, aluminum foil, or heavy clothing.


Gamma radiation: Extremely high

  • External biological damage: Deep tissue, whole-body, and systemic internal organ damage.

  • Gamma rays are not particles with mass—they are high-energy electromagnetic waves (photons). They travel right through clothing, skin, and superficial muscle without slowing down significantly.

  • 1. The Direct Hit: The gamma ray collides directly with your DNA, snapping the strands like cutting a ladder in half. If the cell can't glue it back together properly, the cell either dies or mutates (which can later become cancer).

    2. The "Chemical Grenade" (Indirect Hit): Your body is mostly water. When a gamma ray smashes into a normal water molecule inside a cell, it breaks it apart into a hyper-reactive, toxic chemical fragment called a free radical. That free radical immediately attacks and corrodes the cell's DNA and machinery from the inside out.


Positron: is the antimatter twin of an electron: it has the exact same negligible mass (mass number = 0), but carries a positive charge (+1). Because it behaves like a positively charged beta particle.



Acute Radiation Exposure

Definition: A large dose of radiation delivered over a very short period (seconds to a few days).


Chronic Radiation Exposure

Definition: Low to moderate doses of radiation absorbed repeatedly or continuously over an extended period (months to an entire lifetime).