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Well you have 1. ionic 2. Covalent 3. Polar Covalent 4. Hydrogen bonding Bonds are classified based on the difference in electronegativity between the to atoms. but before we get into that let's talk about the type of bond first. 1.Covalent bond: electrons are shared between atoms. 2.Ionic Bond: electrons are transferred from one element to another. 1. In a covalent bond, we have electrons being shared between to atoms. now depending on how they are shared, electrons can be shared equally or un equally. this depends on the electronegativity. now let's see an example Below let's say we have the a bond between to atoms that are similar: these are called the di-atomic gasses: F2 N2 H2 Cl2 F2 I2 Br2 O2 DI = two atomic means a gas that has two atoms. the diatomic gases are gases at room temperature except for Bromine/Iodine i think those are liquids. Let's say we take one of those at the top. say I2 Iodine. we draw out the lewis structures below and we find that each has 7 valence electrons. So each Iodine atom contributes one electron and shares another, so in this bond each iodine has 8 valence electrons. Now, this is a covalent bond because atoms are shared, and how are they shared? well the electronegativity difference will tell you this. Because Both Iodine elements have the same electronegativity, the atoms are shared equally, so this is non polar covalent. |dw:1441153231535:dw| The next type of bond is polar covalent/hydrogen bonding. polar covalent is the same, as non polar covalent, with the exception that now there is a difference in electronegativity so the electrons aren't shared equally. Let's look at water. Water has 6 valence electrons so it needs two electrons to fill it's octet, so it gets the two electrons, one from each hydrogen. now you might ask yourself this question: Because the oxygen is more electronegative than hydrogen, the electrons spend more time near the oxygen then they do the hydrogen, so what this does is that it's more likely that you'll have electrons near the oxygen than the hydrogen. what this does is it creates a partial negative on the oxygen because more electrons spend more time there, and a partial positive on the hydrogen. this is what we mean by polar. we can say that this type of molecule is polar covalent. |dw:1441153620715:dw| now hydrogen bonding is another type of polar covalent bonding that's usually requires you to have a highly electronegative atom like Oxygen, Fluorine, or Nitrogen that has two things: Both a lone pair of electrons to act as a hydrogen bond acceptor and a hydrogen bonded to it to act as a hydrogen bond donor. i'll show you this in a little bit. |dw:1441153966982:dw| NOW hydrogen bonding is going to cause the boiling points of your compounds to be unusually high why? because for water at least you see that hydrogen bonding causes bonds to form between water molecules. what this does is that you need more energy to break all these bonds between molecules to get water to boil. This makes the boiling point high for these compounds. Now the other type is called ionic bonding. Ionic bonding happens between a metal and a non metal. covalent bonding usually happens between non metals. for this we need to understand how a metal operates. Metals like to lose electrons, because doing so makes them closer to achieving octet. Non metals like to gain electrons. let's see how this happens. Let's take NaCl, salt. Sodium has 11 electrons, and it one valence electron. Sodium wants to lose that electron badly because it's so close to having a configuration like Neon Chlorine wants to gain an electron so badly because if it does it will have 18 electrons a configuration like Argon. |dw:1441154365555:dw| So here's what happens. The electron from sodium is transferred to chlorine to give chlorine a negative charge and sodium a positive one. this isn't really a bond because electrons arent shared, they are transferred. |dw:1441154634895:dw|
I guess another type is called coordinate covalent bonds: the situation here is as follows: like let's say if you have a bond right? we know that typically both elements contribute an electron. but another example is if only one element contributes an electron. for example say you have AlCl3 a lewis acid, and Cl- the chlorine makes a bond with aluminum but both electrons came from chlorine. it's still covalent but that's what you should watch out for. |dw:1441155249856:dw|