Symbol (chemistry) the material was known in ancient times, while for others, the name is a more recent invention. For example, "He" is the symbol for helium (New Latin name, not known in ancient Roman times), "Pb" for lead ("plumbum" in Latin), and "Hg" for mercury ("hydrargyrum" in Greek). Some symbols come from other sources, like "W" for tungsten ("Wolfram" in German, not known in Roman times). Temporary symbols assigned to newly or not-yet synthesized elements use 3-letter symbols based on their atomic numbers. For example, "Uno" was the temporary symbol for hassium (element 108) which had the temporary name of "unniloctium".
Melting point "ΔH" are respectively the temperature at the melting point, change of entropy of melting and the change of enthalpy of melting. The melting point is sensitive to extremely large changes in pressure, but generally this sensitivity is orders of magnitude less than that for the boiling point, because the solid-liquid transition represents only a small change in volume. If, as observed in most cases, a substance is more dense in the solid than in the liquid state, the melting point will increase with increases in pressure. Otherwise the reverse behavior occurs. Notably, this is the case of water, as illustrated