1. Atomic Structure
February 23 & 24

2. Elements Substances that cannot be broken down into other substances.
You should all know this already!
Example: Gold cannot be broken down into anything other than gold.

3. Atoms The smallest particles that have the properties of an element.
Example: A single gold atom will have all of the properties of a large chunk of gold!

4. Atomic Structure
Atomic Nucleus- Contains positively charged (+) protons and neutrally charged (0) neutrons.
Every element has a specific number of protons.
Example: Every atom of hydrogen has 1 proton.
Example: Every atom of helium has 2 protons.

5. Atomic Structure
Surrounding the nucleus are negatively charged (-) electrons.
They whirl around the nucleus in specific orbits.
Electrons are tiny compared to protons and neutrons
It takes more than 1,800 electrons to equal the mass of a proton or neutron.

6. Atomic Charge Atoms are electrically neutral.
Their protons and electrons balance out.
THIS IS NOT ALWAYS THE CASE!
We will cover this next class!

7. Thinking…
Where is most of an atom’s mass? Inside or outside the nucleus?
A sodium atom has 11 protons and 11 electrons, so it is neutral. If the atom lost 1 electron, would the atom stay neutral, become positive, or become negative?

8. Electron Shells
In every atom, electrons exist in fixed energy levels called electron shells.
The lowest energy level can hold a max of 2 electrons
The next energy level can hold a max of 8 electrons
Example: A neutral carbon atom has 6 electrons. The first level can hold 2 electrons. The next level is holding 4 so it could really hold 4 more before it is full.
The highest energy level with any electrons in it is called the outer shell.
Atoms can have up to 7 energy levels.

9. Thinking… How many protons are in a carbon atom?
A hydrogen atom has 1 proton. How many electrons are in its outer shell?