Page 10 - Curriculum Visions Dynamic Book

Native elements
An element is described as ‘native’
if it occurs in the Earth’s crust in an uncombined state as the element
itself (elemental state) rather than as a compound.To exist in a native state,
an element must be relatively unreactive.
There are some 18 native elements, none of which is very common. Of the metals, native gold, silver, copper, tin and platinum are the most commonly found and can be mined as ores.
 Diamond is one of two forms of native or elemental carbon.This piece of Kimberlite rock shows the way in which most diamond occurs, as a dull yellowish mineral set in a rock background. Only occasionally does a transparent and flawless piece of mineral occur.The cut diamond placed on the rock shows the comparison.
 Graphite is one of two forms of native or elemental carbon.
 This diagram represents the structure of graphite. It is made up only of carbon minerals and is, like diamond, an unreactive substance. However, because the structure is in sheets, the bonds between the sheets are relatively weak, so that when pressure is applied, parts of the mineral flake off.That is what allows graphite to be used in pencils.
 This diagram represents the structure of diamond.
It is built of interlocking carbon atoms with no room for other atoms to form part of the structure.That is what makes the mineral so unreactive.
 Radon gas is an elemental gas and is radioactive. Radon gas is most concentrated over igneous rocks such as granite (below). Overall, radon contributes about 32% of the background radiation we experience.
10