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two or more forms of a particular chemical element, that have the same number of protons in the nucleus but have different numbers of neutrons in the nucleus. The different possible versions of each element are called isotopes.
a biological classification group (taxon) that is divided into families.
simple inorganic chemical substances (mineral salts) that are needed in very small amounts for...
regions in particular geographical locations with similar climates and vegetation types.
the practice and science of classification. This is the part of systematics that is only...
a layer of ozone gas which occurs naturally in the upper atmosphere, and protects life by...