Physics Atomic structure and Radioactive decay — 6-topic bundle

The total number of protons and neutrons is the mass number (A). Isotopes of an element have the same number of protons but different numbers of neutrons.

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Let's break down the main types:

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Before the Bohr model, physicists knew atoms had a nucleus and electrons, but they couldn't explain why electrons didn't just spiral into the nucleus (which classical physics predicted). They also couldn't explain the discrete "lines" of light (atomic spectra) emitted by excited atoms.

Niels Bohr proposed a model for the hydrogen atom that introduced a few key ideas:

Radioactive decay is a random process at the atomic level, meaning you can't predict exactly when a single atom will decay. However, when you have a vast number of atoms, the decay follows predictable statistical rules. This is where half-life comes in.

The half-life ($t_{1/2}$) of a radioactive isotope is the time required for half of the initial quantity of that isotope to decay. It's a fundamental characteristic of a specific radioisotope and doesn't change with temperature, pressure, or chemical environment.

For a long time, people thought atoms were the smallest, indivisible particles of matter. This idea, first proposed by Democritus in ancient Greece, was later formalized by John Dalton in the early 19th century.

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