1. Structure of the Atom
Atom -- smallest particle of an element that has all the properties of that element.
3 main subatomic particles:
1. protons
2. neutrons
3. electrons
nucleus -- core of the atom, it is positively charged.
99.9 % of the atoms mass is in the nucleus.
Protons and neutrons are found in the nucleus.
Label the nucleus on your diagram.

2. Protons -- have a positive (+) charge.
(label the protons on your diagram)
The number of protons determines what element an atom is.
Boron (B) – has an atomic # of 5
Boron (B) has 5 protons
Atomic Number = the number of protons, each element has it own unique number of protons.

3. To find just how many neutrons an atom has you:
2. Neutrons -- a neutral charge (no charge) found in the nucleus. These determine whether an element is radioactive.
Label the neutrons on your diagram.
Protons and neutrons are about one atomic mass unit (amu). Electrons have a much smaller mass -- it takes almost 2000 electrons to equal 1 amu.
Atomic Mass (mass number) = the total number of protons and neutrons.
To find just how many neutrons an atom has you:
# neutrons = atomic mass – atomic #

4. 3. Electrons - have a negative (-) charge
3. Electrons - have a negative (-) charge. Found moving around the atom is a space called orbitals (shells).
Label the electrons on your diagram.
Those electrons farthest away from the nucleus are called valence electrons, and are involved in the formation of chemical bonds.
In a uncharged atom the number of protons is equal to the number of electrons.

5. Ions Ion - when an atom gains or loses an electron. (has a charge)
If an atom gains electrons = negative (-) charge.
If an atom loses electrons = positive (+) charge
Chlorine wants to fill its outer shell so it gains an electron and it becomes a negative ion
It now has 18 electrons not the “normal” 17 of an uncharged Cl atom.

6. Atomic Models How to find: # protons = atomic #
# neutrons = atomic mass – atomic #
# electrons = atomic # -- charge (if any)
Name of Element ____________
Protons: _______
Neutrons: ________
Electrons: _________

7. Use index cards to create Vocabulary flashcards
You will use the blue textbook’s glossary for definitions
Atom
Nucleus
Proton
Electron
Neutron
Atomic Number
Atomic Mass
Ion
Valence Electron