Lecture Notes

What is the atomic number of H? Hydrogen is an element in group 1 of period 1 of the periodic table. The atomic number of hydrogen is 1. Hydrogen is denoted by the symbol H and is a nonmetal. History and Uses of Hydrogen It takes its name from the Greek word hydrogenes, which means "to form water". It was discovered by Henry Cavendish in 1766. The name hydrogen was given by Antoine Lavoisier. Robert Boyle obtained pure hydrogen gas. After these discoveries, it was understood that water was not an element. Hydrogen atoms have only one proton in their nuclei. It has three known isotopes with mass numbers 1, 2, and 3. In 1931, a rare isotope of hydrogen was discovered, containing a neutron in addition to a proton in the atomic nuclei. Scientists named this isotope deuterium, known as "heavy hydrogen" because it weighs about twice as much as ordinary hydrogen. Although it is the most abundant element in the universe and on Earth, it is found in very small amounts (<1