1. Topic: Element Identity and Reactivity
Essential Question: What do the protons and valence electrons determine about an element?

2. Topic: Element Identity and Reactivity Essential Question: What do the protons and valence electrons determine about an element?
Protons The number of protons is used to identify an element The atomic number on the periodic table is the number of protons For example: an atom of Carbon has 6 protons

3. Atomic Number = Protons = Electrons
A = P = E
Atomic Number = Protons = Electrons

4. Topic: Element Identity and Reactivity Essential Question: What do the protons and valence electrons determine about an element?
Electrons The number of electrons = the number of protons For example: Carbon has 6 protons and 6 electrons

5. Electron Clouds
Electrons travel around the nucleus in a region called the electron cloud. This is the most accurate model of the atom.
Unlike the electron cloud model, the Bohr model of the atom shows electrons orbiting the nucleus in set paths called energy levels.

6. Bohr’s Electron Model
The first energy level can hold no more than two electrons.
The second energy level can hold no more than eight electrons.
The third energy level can hold no more than eight electrons.
Lower energy levels must be filled before going to higher levels.

7. Bohr’s Electron Model

8. Topic: Element Identity and Reactivity Essential Question: What do the protons and valence electrons determine about an element?
Valence Electrons Electrons located on the outermost shell of an atom They determine the reactivity of an element

9. Topic: Element Identity and Reactivity Essential Question: What do the protons and valence electrons determine about an element?
Valence electrons
Elements with 8 valence electrons are stable (won’t react)
Elements with less than 8 valence electrons are reactive
For example, Sodium, which has 1 valence electron, reacts with Chlorine, which has 7 and creates NaCl, which is table salt Cl Na

10. Now take some time…
1. What do the protons determine about an element? 2. What can you also figure out if you know the number of protons? 3. What is a valence electron? 4. What do the valence electrons determine about an element?