Chemical element whole number. For example, the relative atomic mass of chlorine is 35.453 u, which differs greatly from a whole number as it is an average of about 76% chlorine-35 and 24% chlorine-37. Whenever a relative atomic mass value differs by more than 1% from a whole number, it is due to this averaging effect, as significant amounts of more than one isotope are naturally present in a sample of that element. Chemists and nuclear scientists have different definitions of a "pure element". In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the
Shade (shadow) Shade (shadow) Shade is the blocking of sunlight (in particular direct sunshine) by any object, and also the shadow created by that object. Shade also consists of the colors grey, black, white, etc. It may refer to blocking of sunlight by a roof, a tree, an umbrella, a window shade or blind, curtains, or other objects. In temperate and tropical zones (most places on Earth), shade is an important issue in providing cooling and shelter from harmful heat and ultraviolet emitted by the Sun. Green plants produce shade by absorbing sunlight to invest as energy in photosynthesis to produce sugar.