Chemistry Quick Revision: Atomic Structure & Classification of Elements

Study Notes

The modern periodic table is a tabular arrangement of elements, organized by their atomic number (number of protons), electron configuration, and recurring chemical properties.
Elements can be classified into metals, non-metals, and metalloids.

An atom is the smallest part of an element that has the chemical properties of that element.
Atoms are made up of three subatomic particles: protons, neutrons, and electrons.
Protons have a relative mass of 1 and a positive charge, and are located inside the nucleus.
Neutrons have a relative mass of 1 and no charge, and are located inside the nucleus.
Electrons have a negligible mass and a negative charge, and move around the nucleus.
An atom is electrically neutral because the number of protons is equal to the number of electrons.

Atomic number (Z) of an atom is equal to the number of protons in the atom.
Mass number (A) of an atom is equal to the number of protons + number of neutrons in the atom.
The atomic number (Z) and mass number (A) of an atom are usually shown in a full atomic symbol as: A Z X

Isotopes are different atoms of the same element, with the same number of protons but different numbers of neutrons.
The relative isotopic mass of an isotope is roughly equal to its mass number.
The relative atomic mass of an element is the weighted average of the relative isotopic masses of all the naturally occurring isotopes of that element on the 12C = 12.00 scale.

Metals are typically solids (except mercury), have a shiny appearance, high melting and boiling points, and are good conductors of heat and electricity.
Non-metals are typically gases or solids, have a dull appearance, low melting and boiling points, and are poor conductors of heat and electricity.
Metalloids (semi-metals) have properties intermediate between metals and non-metals, examples include boron and silicon.

Podcast