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A Guide To Chemical Bonding
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Ionic bonding is the bonding between
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Hi, I'm Donald Sinclair. I'm a Science teacher with Greater London Tutors and today, we are going to be looking at a few topics in Chemistry. This is a guide to different types of chemical bonding. Ionic bonding is the bonding found between metals and non-metals. If we look at a diagram of a metal and a non-metal, you can see why. Sodium has eleven protons in its nucleus and eleven electrons orbiting it. This means it has an overall charge of zero. Chlorine similarly has seventeen protons and seventeen electrons. Now, atoms are generally more stable when they have a full outer electron shell. The easiest way for sodium to gain a full outer electron shell, is to lose the one electron it has in its outer layer. This is because it is a metal. It is found on the left of the periodic table, which means it has one; metals generally have one two or three electrons in their outer shell. Non-metals like chlorine however are on the right side of the periodic table. This means that the easiest way for them to gain a full outer electron shell, is to gain, one, two, or three electrons. Chlorine for example, has seventeen protons and seventeen electrons and if it was to gain just one more electron, it would have a stable, full outer shell. So when sodium and chlorine react, they can do a sort of trade. If the sodium loses one electron and the chlorine gains that electron, both atoms are now more stable. They have full outer electron shells. However, because sodium has now lost an electron, it has more protons than electrons. So it has an overall charge of plus one. Chlorine similarly has gained an electron, so it has gained a negative charge and so it now has an overall charge of minus, because it has more electrons than protons. Positive charges are attracted to negative charges and vice versa. This means that the sodium and the chlorine atoms, or ions as they are now because they have gained a charge, will bond together to form a very strong bond. Covalent bonding is another way of an atom gaining a full, outer, stable electron shell. It occurs between non-metals and non-metals, unlike ionic bonding. Let's look at an example. Oxygen has an atomic number of eight. That means it has eight electrons orbiting it. I have omitted the inner shell here, because that takes no part in the chemical reaction. So we can see there are six remaining electrons in the other shell. It needs to gain two more to complete that shell. Similarly hydrogen, the first element, has an atomic number of one. It has one electron in its shell. It needs to gain one more and it will have a full outer electron shell. Normally hydrogen of course is diatomic. So these two hydrogen atoms would be bonded together, but just for simplicity I have separated them into individual atoms. By bonding with the oxygen atom, each of the three atoms can gain their full outer electron shell. In essence, they share the electrons between the three of them. Oxygen now has one, two, three, four, five, six, seven, eight electrons, a full outer shell, and each of the hydrogens has two electrons, a full outer shell. Covalent bonding tends to form small discrete molecules. For example H20, or methane, which is CH4 and these molecules are separate and can float around on their own. That's why a lot of covalent substances tend to be liquids or gases, as opposed to ionic substances, like sodium chloride, which form large, gigantic molecules in a very crystalline, well ordered lattice. Metals, such as iron, gold, silver, have their own particular type of bonding. Metals have layers of positive ions, one over the other and surrounding these ions is a sea of free electrons, which are free to move. This explains why metals are such good conductors of electricity, because the electrons are not tightly bound to any specific ion, to any specific nucleus, they are free to move in the presence of an electric field. This also explains why metals are
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