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Supporting files for this material can be found here. 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.
Resources & Tutorials Chemistry Videos
Chemistry Games
Supporting files for this material can be found here. |
