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    • #6 - Atom Bonding

    Look at the periodic table; you know from lesson one that:
    Metals are on the left, and non-metals on the right, they are separated by a staircase line going down from Boron(B) to Astatine(At)

    Cool. Now you�ve heard of metals, and non-metals. There must be a million differences between these. Including that metals are metallic, and non-metals aren�t. Here are the chemical differences:

    Metals
    Non-Metals
    - Always gives electrons - Takes electrons from metals
    - Can share electrons with other non-metals
    - Always forms ionic bonds - Can form both ionic and covalent bonds
    - Only bonds with non-metals - Bonds with both metals and non-metals

    Now what is an ionic, or covalent bond? Well, ionic bonds have only one metal element, and non-metal element; for example, NaCl is an ionic bond because it contains only a metal (Na), and a non-metal (Cl), so is Al2O3, two metal aluminum atoms(Al) are joined with three non-metal oxygen atoms(O) to form an ionic bond.

    Covalent bonds have two or more non-metal elements; for example CO2 is a covalent bond because it has two non-metal elements, carbon(C), and oxygen(O).

    Now what drives these two atoms together? Electrons!(exciting I know) How? Well remember from the last lesson that atoms try to achieve 0 or 8 electrons in their outer shell by forming bonds with other atoms(Octet Rule), well here is the table from the last lesson.

    Atoms in columns Numbers of electrons in outer shell
    H, Li, K, Rb, Cs, Fr
    1
    He, Be, Mg, Ca, Sr, Ba, Ra
    2
    B, Al, Ga, In, Ti
    3
    C, Si, Ge, Sn, Pb
    4
    N, P, As, Sb, Bi,
    5
    O, S, Se, Te, Po
    6
    F, Cl, Br, I, At
    7
    Ne, Ar, Kr, Xe, Rn
    8

    With ionic bonds, you already know a metal is joined with a non-metal, and that each atom involved either achieves 0 or 8 in their outer shell (Octet Rule), and that the metal gives up electrons while the non-metal takes electrons. Now just how many electrons are given or taken? As many as needed for every atom involved to have 0 or 8 electrons in it�s outer shell.

    For example, NaCl is an ionic bond, Na has one electron in it�s outer shell, Cl has seven. Na gives the one electron to Cl, so Na can have 0, and Cl can have 8.

    Na
    Cl
    1. - Has one electron in outer shell -Has two electrons in outer shell
    2. - Gives that electron to Cl - Takes the electron from Na
    3. - Has zero electrons in outer shell - Has eight electrons in outer shell

    A picture can also be drawn.

    Now some ionic bonds have more than just one metal atom and one non-metal atom. For Example, Al2O3 has two aluminum atoms and three oxygen atoms, here�s how they form:

    Al
    O
    1. - Has three electrons in outer shell - Has six electrons in outer shell
    2. - Two Al�s give six electrons
    (three each) to three O�s     		- Three O�s takes those six electrons from Al and takes two each
    3. -Two Al�s have zero electrons in outer shells - Three O�s have eight electrons in outer shells

    A Picture can also be drawn.

    Now, with Covalent bonds, two or more non-metal atoms share a certain amount of electrons until they each have eight in their outer shell.

    For example, CO2 is a covalent bond that has one carbon atom(C), and two oxygen atoms(O). carbon has four electrons in it�s outer shell, it can share four more electrons, two with the first oxygen atom, two with the other, since each oxygen atom has 6 in it�s outer shell and needs two more to get to eight, they share two of their electrons with the C so all three have eight electons.

    Here�s a picture to help:

    I hope this lesson helps you understand the basic principal of bonding, The next lesson will tell you how to form one of these bonds.

    Review:

    • ionic bonds have only one metal element and one non-metal element
    • ionic bonds involve a non-metal taking electrons from a metal so that they can achieve 0 or 8 in their outer shell
    • covalent bonds have two or more non-metal atoms
    • covalent bonds involve these non-metal atoms sharing electrons so that they can achieve 0 or 8 in their outer shell
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