The ae element periodic table was published in 1869 by Russian scientist Dmitri Mendeleyev. The table is a series of chemical elements arranged in order to show how their properties change over time.
Elements in the same group share similar valence (outermost) shell electron configurations, and exhibit similar chemical properties. The number of valence electrons in a period generally increases from left to right, but the IE and EA are opposite: * Atomic size increases across a period as Zeff increases: a more positive electron is added to the valence shell of a larger atom. It is harder to remove an electron from a large atom than from a smaller one.
In addition, atomic size decreases down a group as IE decreases: valence electrons are further away from the nucleus and held less firmly. Likewise, IE of nonmetals (except noble gases) is generally lower down a group as the added electron is more likely to become an ion.
Metals are solids because strong metallic bonds hold atoms together in their crystal structures, while nonmetals are liquids or gases due to weaker dispersion forces between atoms. The heat of fusion and vaporization is also related to the strength of the bonding or dispersion forces between atoms.
Symbols: Every element has a one or two letter international symbol. Most symbols are derived from the English name of the element, but some symbols stem from ancient Latin and Greek vocabulary.
Names: Most elements have an official IUPAC-approved name. However, names of some elements are disputed.