Elements

Organization and properties of elements, patterns in the periodic table, and element families.

The alkali metals are the highly reactive metals in Group 1 of the periodic table. They react vigorously with water and air, producing hydrogen gas and metal hydroxides. Their reactivity increases going down the group.

Every element has a one- or two-letter symbol used worldwide. Chemical formulas combine these symbols with numbers to show exactly which atoms are present in a substance and how many of each.

The periodic table is arranged in vertical columns called groups and horizontal rows called periods. An element's position tells you about its structure and properties.

The halogens are reactive non-metals in Group 7. They exist as diatomic molecules and become less reactive going down the group. Halogens react with metals to form salts, and are used in water purification, disinfectants, and plastics.

Metals are elements on the left and centre of the periodic table. They share characteristic properties such as shininess, electrical conductivity, malleability, and high melting points, which make them useful in everyday life.

Noble gases are the elements in Group 18 of the periodic table. They are colourless, odourless gases that are extremely unreactive because their outer electron shells are completely full.

Non-metals are found on the right side of the periodic table. They are generally poor conductors of heat and electricity, often exist as gases at room temperature, and their solid forms are brittle — yet they are essential to life and many chemical reactions.

The periodic table is a chart of all known elements arranged in order of atomic number. Elements in the same column share similar chemical properties, which makes the table an extremely useful tool in chemistry.

The transition metals are found in the central block of the periodic table. They are strong, dense, and good conductors with high melting points. Unlike Group 1 and Group 7 elements, they are much less reactive and form coloured compounds with multiple oxidation states.