Chemistry

Atomic Structure

Everything that we know of in this universe can be divided into two categories: matter or energy. All the "stuff" in this universe gets a fancy name called matter. You are matter, this computer is matter, the chair you are sitting in is made of matter. The smallest unit of matter is an atom.

We can not see an atom with our eye because they are so extremely small. Scientist create models of atoms to help us understand them better. There are several different types of models, but in junior high we use the Bohr model of an atom.

A substance that is made up of only one kind of atom (all the atoms have the same number of protons) is called an element. An element is a pure substance which cannot be broken down any further. There are 92 naturally occuring elements. Scientist organize elements on the Periodic Table of Elements.

The Periodic Table of Elements is an amazing tool that can tell us many things about elements and their atoms. The entire periodic table is organized by the number of protons in the nucleus of the atom. This is called the atomic number. I know that the element in the picture above is Lithium because I counted the number of protons in the nucleus. Lithium has three protons so its atomic number is 3 on the periodic table.

Atom Facts:

1. The atomic number = the number of protons

2.The atomic number = the number of electrons

3. The atomic mass = the number of protons + the number of neutrons

4. Number of neutrons = round atomic mass, then atomic mass - atomic number

Periodic Table

Quizlet Periodic Table Vocab Review

But how do you know how many energy levels (or electron clouds) an element has when you're drawing a model? The answer can be found on the periodic table! All you do is look at the period, or row, that the element is found in. Every element in period 1 has one energy level, elements in period 2 have two energy levels...

The vertical columns on the periodic table are called groups, or families. All the elements in the same group have the same number of valence electrons (electrons in the outer energy level.) Elements in the same groups all have similar properties. This is because they have the same number of valence electrons. Therefore, it is the valence electrons that give elements their physical and chemical properties.

Because the elements are also grouped into columns by similar properties, the entire periodic table can be further divided into three groups: metals, nonmetals, and metalloids. Look at your lab assignment "What is a Metal?" on page 2 to see the properties of metals and nonmetals. Metallods have properties of both metals AND nonmetals.

Blue = Metals, Yellow = Nonmetals, Pink = Metalloids

Click on the following link for an interactive Periodic Table and learn about some of the uses of the elements. http://elements.wlonk.com/ElementsTable.htm

Chemical Formulas, Equations, and Reactions

How to Balance Chemical Equations.

Below are resources to help you learn how to balance chemical equations.

Copy of the test review.

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