Chemistry : Chemical Groups

 

The broad classifications of the elements is metals and non-metals.  Each of these groups can then be further divided and categorized.

METALS

Metals form the majority of the elements and their chemical reactivity ranges from gold, which is found ‘native’ (uncombined),to metals such as potassium and sodium. Metal oxides are basic. A basic oxide is able to react with an acid to produce a salt and water only, for example:

MgO  + H2SO4  fi MgSO4 +  H2O

magnesium  sulphuric   magnesium   water

oxide  acid   sulphate

The alkali metals are the most reactive metals in the Periodic Table. These elements – lithium, sodium, potassium, rubidium, caesium and francium -(located in group 1 of the Periodic Table) are soft metals. Their softness and low melting point are the result of the weakness of their metallic bonding. The alkaline earth metals are the elements of group 2 – beryllium, magnesium, calcium, strontium, barium and radium. Of these elements, calcium and magnesium are the most common. The alkaline earth metals are not as reactive as the alkali metals.

NON-METALS

Non-metals’ atoms generally have four, five, six or seven electrons in their outermost shells. By sharing electrons with other non-metal atoms, so as to create ‘bonding-pairs’ of electrons, non-metal atoms can manage to resemble their aristocratic  cousins, the noble gases. Nonmetal oxides are either acidic or neutral.

Noble gases : The noble gases, a family of elements found on the far right of the Periodic Table, are extremely unreactive. This seems to be associated with the fact that they have an especially stable arrangement of electrons in their outermost shells.

Halogens : Halogens, consistingof fluorine, chlorine, bromine and iodine (plus astatine), are reactive non-metals. Halogen atoms have one electron less in their outer shells than noble gases, and must gain an electron to gain a stable structure, making them reactive. Halogens react vigorously with metals and hydrogen to form halides (organic compounds with halogen atoms in their molecules).

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