Everyone at that time imagined the atom as a "plum pudding ... of light emitted by real hydrogen atoms. Bohr's theory that electrons existed in set orbits around the nucleus was the key to ...

Heavy water is a form of water with a unique atomic structure and properties ... molecule of heavy water contains two hydrogen atoms and one oxygen atom. The difference, though, lies in the ...

The dot and cross diagram shows that a water molecule is made up of one oxygen atom joined to two hydrogen atoms, so the formula of water is H 2 O. A nitrogen molecule is made up of two nitrogen ...

An element's atomic number defines it. An element with 17 protons will always be chlorine. However an element's mass numbers can vary, which means that it can have different numbers of neutrons.

This image illustrates the general structure of an amino acid.The central carbon atom (C) is bonded to a hydrogen atom (H), an amino group (NH2), a carboxyl group (COOH), and a variable side chain (R ...