What is an Atom?

Embark on a journey into the microscopic world, where we'll explore the fundamental building blocks of everything around us - atoms. Unravel the mysteries of these tiny particles, their structure, and their immense influence on the universe.

More

Atoms are the basic units of matter and the defining structure of elements.

• They are made up of three particles: protons, neutrons, and electrons – which are composed of even smaller particles such as quarks.
• They were created in the Big Bang 13.7 billion years ago, when conditions became suitable for quarks and electrons to form.

History of the Atom

The theory of the atom dates back to 440 BC to Democritus, a Greek scientist and philosopher.

• His explanation included the ideas that atoms exist separately from each other, that there are an infinite amount of atoms, that atoms are able to move, that they can combine together to create matter but do not merge to become a new atom, and that they cannot be divided.

Atomic particles

Protons and neutrons are heavier than electrons and reside in the nucleus at the center of the atom.

• Adding a proton to an atom makes a new element, while adding a neutron makes an isotope, or heavier version, of that atom.

Neutrons

The neutron is used as a comparison to find the relative mass of protons and electrons.

• It has a physical mass of 1.6749×10-27 kg and was theorized by Rutherford in 1920 and discovered by Chadwick in 1932.

Nucleus

Discovered in 1911 by Ernest Rutherford, a physicist from New Zealand

• Virtually all the mass of the atom resides in the nucleus
• The protons and neutrons that make up the nucleus are approximately the same mass (the proton is slightly less) and have the same angular momentum

Isotopes

The number of neutrons in a nucleus determines the isotope of an element. For example, hydrogen has three known isotopes: protium, deuterium, and tritium: hydrogen has one proton, one electron, and one neutron.

Protons

These are positively charged particles found within atomic nuclei.

• The number of protons in an atom is referred to as the atomic number of that element.
• They are slightly smaller in mass than neutrons with a relative mass of 0.9986 vs. 1.673×10-27 kg.

Electrons

Electrons are tiny compared to protons and neutrons, over 1,800 times smaller than either a proton or a neutron.

• They have a relative mass of 0.0005439 (as compared with the mass of a neutron being 1) or about 9.109×10-31 kg.

Source