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Water for life
Water for life

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You have learned about the following concepts in this course:

  • Each type of atom contains a characteristic number of protons in a central nucleus and an equal number of electrons in layers surrounding the nucleus.

  • Elements are substances that consist of only one type of atom. Compounds contain two or more elements combined together. There are two kinds of bond between atoms: covalent and ionic.

  • Molecules are the smallest units in which elements and/or compounds can exist covalently bonded together.

  • Ions are formed by atoms or groups of atoms gaining or losing electrons.

  • Chemical formulas describe the number of atoms present in elements, ions and compounds.

  • Balanced chemical equations describe, using chemical formulas, the reactants and products in a chemical reaction.

  • Concentration is the mass of a substance dissolved in a given volume (usually 1 litre) of a liquid.