“WATER IS A GOOD SOLVENT”
Water is very unique in all facets of its nature. The chemical formula for water is H2O as a water molecule consists of two atoms of the chemical element hydrogen (H) and one atom of the element oxygen (O). Water is the most abundant chemical compound on earth as its mass all exists together, naturally, in its gaseous, liquid and solid state. It is the most precious natural resource to man and is essential to life for all discovered living organisms. One of the unusual things about water is that, unlike any other substance, it is constantly moving in the environment, readily changing from state to state in a cycle which is known as the water cycle or the hydrological cycle. The solid state of water is known as ice and the gaseous state is known as vapour or steam. Water can never be found in the environment as pure H2O. It is always found with some kind of impurity dissolved in it. This is because many compounds can readily dissolve in water from its surrounding environment. Why is that? All of the peculiar characteristics of water are a result of the interactions between the outermost electrons of the constituent hydrogen and oxygen atoms. They are involved in a chemical process known as bonding. In chemistry there are various types of bonding. They are all a result of electrons interacting with each other. Atoms interact by transferring, sharing or rearranging their electrons in a way that allows them to achieve a full shell of electrons which makes the atom stable. In compounds, there are two main types of bonding; ionic bonding and covalent bonding. Ionic bonding is usually found in compounds of a metal and a non-metal. This type of bonding involves the complete transfer of at least one electron from one atom to another. It is normally the metal atom which donates the electron or electrons to the recipient non-metal atom. The donor metal atom usually has very few or a single electron in its outer most shell which it readily loses leaving a stable, filled inner shell of electrons immediately below it. This produces a positively charged atom called a cation. The atom becomes positively charged because the atom has less negatively charged electrons, than it has positively charged protons, leaving the overall charge of the atom as positive. The donor metal atom gives its electrons to the receiving non-metal atom. The recipient non-metal atom, whose outermost shell is almost complete, accepts the electron (or electrons) to achieve a full and stable outer shell of electrons. The atom gaining the electron (or electrons) becomes a negatively charged anion. The atom gains this charge because it now has more negatively charged electrons, than it has positively charged protons. The electrons move in this direction because the non-metal is, in most cases, more electronegative than the metal component. Electronegativity of an element is a measure of the affinity it has to attract a bonding pair of electrons. A strong ionic bond is now formed as the oppositely charged ions are electro-statically attracted to one another. The molecule formed is known as an ionic compound which will normally be a sub-unit, packed together in a regular structure, forming a giant ionic lattice of that particular compound.
Fig.1. Showing ionic bong in Magnesium Chloride. (Taken from Ritchie, 2008) Bonding in water molecules is, somewhat, different to that of ionic bonding. Atoms in water molecules are held together by a different type of bond known as a covalent bond. This type of bonding is found in compounds where the constituent atoms are non-metals. A covalent bond is formed when “electrons are shared rather than transferred” (Rithchie, 2008). When a covalent bond is formed, each atom involved shares one electron to achieve a shared pair of electrons. This shared pair of electrons is a covalent bond. A compound can also have multiple covalent bonds present between constituent...
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