Elements contain just one sort of atom. Although the atoms of a particular element may differ slightly in mass , they all have identical chemical reactions. Examples of elements include hydrogen gas, copper metal and diamond crystals (which are carbon).
Compounds are made up from the atoms of two or more different elements, bonded together chemically. The ratio of elements within a particular compound is fixed, and is given by its chemical formula . The physical and chemical properties of a compound are always different from those of the elements that make it up. Examples of compounds include sodium chloride (containing sodium and chlorine ions), water (containing hydrogen and oxygen atoms) and penicillin (containing hydrogen, carbon, nitrogen, oxygen and sulfur atoms). • Mixtures consist of more than one compound or element, mixed but not chemically combined. The components can be mixed in any proportion, and the properties of a mixture are often the sum of, or the average of, the properties of the individual components. Examples of mixtures include air, sea water and alloys such as brass.
Compounds are made up from the atoms of two or more different elements, bonded together chemically. The ratio of elements within a particular compound is fixed, and is given by its chemical formula . The physical and chemical properties of a compound are always different from those of the elements that make it up. Examples of compounds include sodium chloride (containing sodium and chlorine ions), water (containing hydrogen and oxygen atoms) and penicillin (containing hydrogen, carbon, nitrogen, oxygen and sulfur atoms). • Mixtures consist of more than one compound or element, mixed but not chemically combined. The components can be mixed in any proportion, and the properties of a mixture are often the sum of, or the average of, the properties of the individual components. Examples of mixtures include air, sea water and alloys such as brass.
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