Hydrogen Properties

Hydrogen is chemically unique in a number of ways. Among these unique features is Hydrogen 's ability to form compounds by giving up an electron or acquiring one. Elements that give up electrons to form compounds are considered electropositive and appear at the left side of the periodic chart of the elements.

On the other hand, elements that gain electrons to form compounds are called electronegative elements, and appear near the righthand side of the periodic chart.

Unique property of Hydrogen

Hydrogen is the one and only element that can do both; Hydrogen can be placed in Group IA (electropositive) or Group VIIA (electronegative). No other element has an ambiguous position on the periodic chart. Most periodic charts show hydrogen in its IA position. A few show Hydrogen in the VIIA position as well.

Diatomic

Hydrogen tends to be diatomic. This means the molecules are composed of two atoms; therefore, the gas is represented symbolically as H₂.

Two types of Hydrogen molecules

There are two types of H₂ molecules, ortho-hydrogen and para-hydrogen.

• In the ortho hydrogen molecule, the two protons spin in the same plane;
• In the para-hydrogen molecule, the spins are in opposite planes.

This affects the magnetic properties and electronic band spectra of the molecules. In ordinary hydrogen gas and normal environmental temperatures, the ratio of ortho- to para-hydrogen is 3:1. The portions are roughly equivalent at - 200°C, and the amount of para-hydrogen approaches 100% as the temperature nears absolute zero.