Page 11 - Curriculum Visions Dynamic Book

A sample from a hydrothermal deposit with elemental copper among quartz
shell and so it is one electron short of a stable set.That is why it is very reactive. Sodium is also reactive because it contains just one electron more than a stable set. When sodium and chlorine combine, or bond together, they therefore are able to transfer electrons to make both shells stable. That is why it is very difficult to separate sodium and chlorine from common salt (sodium chloride).
 Chlorine reacts violently with sodium to produce sodium chloride.
 Colourless silver nitrate solution is added to colourless potassium iodide solution, producing a new
yellow compound of silver iodide.
Elemental gases
There are several elements that also occur naturally in the uncombined state as gases. They include nitrogen, which is the most abundant gas in the atmosphere, oxygen, and the particularly unreactive noble gases such as argon, neon and radon.
Compounds and mixtures
A compound is a single substance made of two or more different elements joined together by links called bonds.
Atoms can form compounds by sharing some of the electrons in their outer shells. When atoms do this, they are said to be bonded together.
Atoms of the noble gases, such as helium and argon, have the most stable number of electrons in their outer
shells, so these electrons are not easily available – that is why they are unreactive. In contrast, atoms of elements without the most stable set of electrons in their outer shell are reactive. Chlorine, for example, contains only seven electrons in its outer
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