Period 3 element

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A period 3 element is one of the chemical elements in the third row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behavior fall into the same vertical columns. The third period contains eight elements: sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon. The first two, sodium and magnesium, are members of the s-block of the periodic table, while the others are members of the p-block.

Overview

All of the period 3 elements occur in nature and have at least one stable isotope.

Elements

Sodium

Sodium (symbol Na) is an alkali metal. It is present in Earth's oceans in large quantities in the form of sodium chloride.

Magnesium

Magnesium (symbol Mg) is an alkaline earth metal. Magnesium ions are found in chlorophyll.

Aluminium

Aluminium (symbol Al) is a poor metal. It is the most abundant metal in the Earth's crust.

Silicon

Silicon (symbol Si) is a metalloid. It is a semiconductor, making it the principal component in many integrated circuits.

Phosphorus

Phosphorus (symbol P) is a nonmetal. It is highly reactive, and as such is never found in nature as a free element.

Sulfur

Sulfur (symbol S) is a nonmetal. It is found in two amino acids: cysteine and methionine.

Chlorine

Chlorine (symbol Cl) is a halogen. It is used as a disinfectant, especially in swimming pools.

Argon

Argon (symbol Ar) is a noble gas, making it almost entirely nonreactive. Incandescent lamps are often filled with noble gasses such as argon in order to preserve the filaments at high temperatures.

Table of elements