Chemistry – The Periodic Table - Arrangement of elements | e-Consult

The modern periodic table arranges elements in a systematic way based on their atomic number, which is the number of protons in the nucleus of an atom. The elements are arranged in periods and groups.

Periods are the horizontal rows of the periodic table. There are currently 7 periods. Elements within the same period have the same number of electron shells. As you move across a period from left to right, the atomic number (and therefore the number of protons and electrons) increases. This leads to a gradual change in the properties of the elements.

Groups are the vertical columns of the periodic table. There are 18 groups. Elements within the same group have the same number of valence electrons, which is the number of electrons in their outermost shell. This similarity in valence electron configuration results in similar chemical properties. The groups are numbered 1 to 18, although historically they were numbered 1 to 8. Group 1 consists of alkali metals, Group 2 consists of alkaline earth metals, and so on.

The elements are arranged in order of increasing atomic number. This means that the element with the lowest number of protons (and electrons) is at the top left of the table, and the element with the highest number of protons (and electrons) is at the bottom right.