Element families: what the colors on the periodic table mean

What makes a family

Elements in the same family behave in similar ways, mostly because they have a similar number of outer electrons, called valence electrons. These outer electrons decide how an element reacts.

Some families sit in a single column, such as group 2 or group 18. Others cover a whole block of the table. The colors are only a code, and different tables use different ones, so always check the key.

Alkali and alkaline earth metals

The alkali metals are group 1, the first column, except hydrogen: lithium, sodium, potassium, rubidium, cesium and francium. They are soft enough to cut with a knife, and they react with water to make hydrogen gas. Potassium reacts so strongly that the hydrogen catches fire with a lilac flame.

The alkaline earth metals are group 2: beryllium, magnesium, calcium, strontium, barium and radium. They are harder and less reactive than their neighbors in group 1. Calcium helps build your bones and teeth, and strontium gives fireworks their red color.

Transition and post-transition metals

The transition metals fill the wide middle block, groups 3 to 12. They include iron, copper, silver and gold, and most of them are hard, strong and shiny. Iron is the most widely used metal of all, mostly in the form of steel.

The post-transition metals sit to their right, just before the staircase line. On this site they are aluminum, gallium, indium, tin, thallium, lead, bismuth and polonium. They are softer and melt more easily than most transition metals. Gallium melts at about 29.8 °C, so it turns to liquid in your hand.

Metalloids and reactive nonmetals

The metalloids lie along the zigzag staircase line: boron, silicon, germanium, arsenic, antimony and tellurium. They are partly like metals and partly not. Silicon, the second most common element in Earth’s crust after oxygen, is the key material in computer chips.

The reactive nonmetals are hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur and selenium. Most of them sit at the upper right, while hydrogen sits at the top of group 1 even though it is not a metal. They are the elements of life: oxygen, carbon, hydrogen and nitrogen make up about 96% of your body’s mass.

Halogens and noble gases

The halogens are group 17: fluorine, chlorine, bromine, iodine and astatine. Their name means “salt-former,” because they react with metals to make salts such as sodium chloride. Chlorine compounds keep swimming pools clean, and fluoride in toothpaste helps protect your teeth.

The noble gases are group 18, the last column: helium, neon, argon, krypton, xenon and radon. Their outer shells are full, so they hardly react with anything. Helium is lighter than air and lifts party balloons, and neon glows red-orange in shop signs.

The two rows at the bottom

The lanthanides (57–71) and the actinides (89–103) are the two rows printed below the main table. They belong in periods 6 and 7 but are moved down so the table does not get too wide.

The lanthanides are soft, silvery metals that are very similar to one another. Neodymium, for example, makes the strong magnets in earbuds and electric motors. The actinides are all radioactive, and uranium is the fuel of nuclear power plants.

One more color marks the superheavy elements from meitnerium (109) to oganesson (118). Only a few atoms of each have ever been made, so this site lists their properties as unknown.