Hydrogen is the lightest and simplest of all elements in the periodic table. One hydrogen atom contains only a nucleus with one proton and no neutrons. Only one negatively charged electron orbits or circles the nucleus. The number of protons and the number of electrons are almost always equal. The number of protons is called the atomic number, and no two elements have the same atomic number.

The periodic table of elements is organised according to the atomic numbers of elements, from the lowest to the highest. Hydrogen has an atomic number of 1, so it is listed as the first element on the periodic table. In addition to having just one proton, hydrogen also has the lowest atomic weight (relative atomic mass) of all the elements. Hydrogen sits on the top periodic table of elements. Because it contains only one proton and one electron, hydrogen’s atomic number is 1. While hydrogen is not the most common element found on Earth, it is the most common element in the universe. The Sun is about 92 per cent hydrogen. The remaining 8 per cent is helium.

Hydrogen in the Periodic Table Group

The atomic weight is the mass of one atom of the element. It is known that hydrogen has the most abundant and lightest element. The periodic table has 118 elements, with 92 found naturally and the rest human-made. Hydrogen is mostly found in the form of a gas, and its chemical symbol on the periodic table is H.

Robert Boyle prepared hydrogen in 1672 by treating iron with sulphuric acid but was unable to establish its elementary character. The credit for the discovery of hydrogen goes to Henry Cavendish, who prepared it by the action of dilute hydrochloric acid with zinc in 1766. He not only established its elementary character but also proved that when hydrogen is burnt in the air, it forms water. Because of its property of water formation, it was named hydrogen by Lavoisier in 1783, as hydrogen means water former in the Greek language.

Hydrogen is the first member of the periodic table. Its electronic configuration is 1s¹. As hydrogen has only one electron in its valence shell, therefore, it belongs to the 1 or IA group of the periodic table.

Why Is the Position of Hydrogen Anomalous?

As hydrogen has only one electron shell, therefore, it belongs to the first period of the periodic table. As hydrogen belongs to the IA group of the periodic table, it is expected that its properties should be similar to the other members of the group, such as lithium and sodium.

However, this is not the case. Lithium and sodium are strong alkali metals, whereas hydrogen is a non-metal. In spite of the above anomaly, hydrogen is placed in Group IA. It is because it forms positively charged ions (H⁺ ions) by donating an electron from its valence shell, much the same way as sodium and lithium. Though it also forms hydride ions [H^– ions] by accepting one electron. In a way, the position of hydrogen is anomalous in the periodic table, and this anomaly is not resolved so far.