Chemistry

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Matter is made up of atoms.  Atoms have three parts:
1. Proton - Has a positive (+) charge, and is found in the nucleus
    of the atom.  Has a mass of 1 amu (atomic mass unit).
2. Neutron - Has a neutral (o) or no charge, and is found in the
    nucleus of the atom.  Has a mass of 1 amu.
3. Electron - Has a negative (-) charge.  Electrons orbit the
    nucleus in electron shells (sometimes called electron clouds).
    Has a mass of 1/2,000 amu.

An element is a substance that contains only one type of atom.  Elements are organized into the Period Table, which sorts them by size.  You can download a Periodic Table here.

A compound is a substance that contains two or more types of atoms (two or more elements).  Organic compounds must contain both carbon (C) and hydrogen (H).

The Periodic Table is set up in such a way that it tells you about the elements and their atoms.  Each period (horizontal row) represents an electron shell.  The first period has two elements in it - which tells you that the first electron shell can only hold two electrons.

Each element in the Periodic Table has a chemical symbol (a letter or two that represents that element), an atomic number (which tells you the number of protons in an element's atom), and an atomic mass number (which tells you the number of protons and neutrons combined in the atom).

For more information on elements, the Periodic Table, and how to properly diagram atoms, please see the "Element Basics" PowerPoint that is attached to this note.

Atoms join together by creating bonds.  The two types of atomic bonds that we cover are covalent bonds and ionic bonds.  Covalent bonds occur when atoms share electrons.  Ionic bonds form when one atom steals electrons from another.  In both cases, the atoms are attempting to have a full outer shell.

When an atom gains or loses electrons, it is no longer an atom.  Instead, it becomes an ion - which is basically an atom that has a charge (positive or negative).  There is a game to help you learn to match ions to their names here.

For example, oxygen has 8 protons, 8 neutrons, and 8 electrons (2 in the first shell, and 6 in the second shell).  The second shell can hold up to 8 electrons, so there are two empty spaces in oxygen's outer shell.  If the oxygen atom picks up two electrons from somewhere else, it will have a full outer shell.  However, the oxygen will now have two extra electrons - which will give it an overall charge of -2.

Isotopes are different forms of an element.  Isotopes of the same element have the same number of protons and electrons, but different numbers of neutrons.  For example:
                    Carbon-12        Carbon-13        Carbon-14
Protons:              6                        6                      6
Neutrons:            6                        7                      8
Electrons:            6                        6                      6

An element that is radioactive is one that changes into another element over a period of time.  The process of one element gradually changing into another is called radioactive decay.  The radioactive element's half-life is the amount of time that it takes for half of the atoms in a sample of the element to change into the new element.  (See the PowerPoint on "Half Life" for more on this.)

 

Chemical Equations

A chemical equation is how we write a chemical reaction.  For example, sodium will react with chlorine to form sodium chloride (salt).  The formula for this is:

      Na  +  Cl  =>  NaCl

Note: You must have the same number and type of atoms before and after the reaction.  If so, then the equation is balanced.

       H2  +  O2  =>  H2O        This is NOT a balanced equation.

       2H2  +  O2  =>  2H2O    This IS a balanced equation.

You can practice balancing equations here.


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