Building Blocks of Matter

Building Blocks of Matter

The periodic table of elements include them all

The periodic table of the elements was first devised in the 19th century to show the atomic weights of the elements and to group them by similar properties. The discovery of protons and electrons in atoms in the early 20th century gave rise to a new and more accurate arrangement of the elements in a periodic table. The new arrangement is based on the atomic number of protons (positively charged particles) present in the atomic nucleus of an element.

The table lists the elements in horizontal rows (or periods), according to their atomic numbers. Each vertical column, except hydrogen in the first column, groups elements that have related properties and are likely to behave similarly in chemical relations. Except for hydrogen, the elements on the left side of the table are metals while those in the last six columns are predominantly non-metals. In those columns, a heavier, stepped boundary line separates the metals from the non-metals.

Everything is composed of matter. Illustration by Elena

Hydrogen is the lightest and simplest element in the table. It has many unique properties different from all other elements. For example, in chemical reactions, it can give up or acquire an electron from other elements, which are incapable of transferring electrons both ways.

Besides the atomic number, the periodical table also lists each element’s name, chemical symbol, and atomic weight (or atomic mass). Atomic weight is the mass of an atom relative to the mass of an atom of carbon-12, which is arbitrarily assigned an atomic weight of 12 by an international convention.