Trivial name for example, hydrogen ("water-producing"), oxygen ("acid-producing"), nitrogen ("soda-producing"), bromine ("stink"), and argon ("no reaction") were based on Greek roots, while the names of iodine and chlorine were derived from the Greek words for their characteristic colors. Indium, rubidium, and thallium were similarly named for the colors of particular lines in their emission spectra. Iridium, which forms compounds of many different colors, takes its name from "iris", the Latin for "rainbow". The noble gases have all been named for their origin or properties. Helium comes from the Greek "helios", meaning "sun" because it was first detected as a line in the
Chemical element their atomic nucleus; so the atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of the same element having different numbers of neutrons are known as isotopes of the element. The number of protons in the atomic nucleus also determines its electric charge, which in turn determines the number of electrons of the atom in its non-ionized state. The electrons are placed into atomic orbitals that determine the atom's various chemical properties. The number of neutrons in a nucleus usually has very little effect on an element's chemical properties (except in the case of