1. Bohr Model Energy levels
How can I draw the electron cloud of the elements by looking at the atomic number?

2. Valence Electrons
We look at atomic number to see the number of protons (and electrons, because the atom must be stable).
The electrons they occupy the highest energy level of an atom.
The outermost energy level is called the valence shell.
Valence electrons play a key role in the chemical properties of an element.

3. -Niels Bohr’s Model – Distinct Energy Levels

4. Valence Electrons In the first ring= up to 2 electrons
Once you fill up of the 2 electrons, move to the second ring.
In the second ring= up to 8 electrons
In the third ring= up to 8 electrons

5. Energy Shells
Each energy shell/level is represented by a circle around the nucleus of the atom.
The first (lowest) energy level holds only 2 electrons
After this level is filled up, electrons go to a higher (outer) E level.
Electrons fill the lower levels and then move to higher (outer) levels.
(No matter how many energy levels there are,
the outermost energy level can only hold at most 8 electrons)

6. Energy Shell Example Carbon: What is its symbol?
What is the atomic number?
What is the atomic mass?
How many protons does it have?
How many electrons does it have?
How many neutrons does it have?
How many electrons go in the first shell?
How many electrons go in the next shell?
How many valence electrons are there?

7. Energy Shell Example Carbon: What is its symbol? C
What is the atomic number? 6
What is the atomic mass? 12
How many protons does it have? 6
How many electrons does it have? 6
How many neutrons does it have? 6
How many electrons go in the first shell? 2
How many electrons go in the next shell? 4
How many valence (last shell) electrons are there? 4

8. Let’s try building Silicon Atom Model.

9. Let’s try building Oxygen Atom Model.

10. Modern Periodic Table

11. Part I Introduction. Periods and groups.
Metals, nonmetals and metalloids.

12. The Modern Periodic Table
The Periodic Table is a listing of all the known elements, developed by Dmitri Mendeleev.
The elements are organized by:
Atomic number
Chemical Properties

13. How do you read the PERIODIC TABLE?

14. Groups and Periods
Group( or Family): a vertical column. Elements in groups have similar chemical properties.
There are 7 Groups/ column.
Period: a horizontal row.
There are 18 numbered rows.

16. Metals, Nonmetals and Metalloids
Elements can be classified into:
Metals
Nonmetals
Metalloids (semimetals)

17. Nonmetals
Metals
Metalloids

19. Physical Properties of Metals
Most elements are metals
Good conductors of electricity and heat.
Malleable (can be hammered into sheets).
Ductile (can be drawn into wires).
Most metals are solid at room temperature
Example: Lithium/ Iron

20. Chemical Properties of Metals
Easily lose electrons.
Form positive (+) ions.

21. Nonmetal Physical Properties
More than half of nonmetals are gas at room temperature
Nonmetals are not ductile or malleable
Nonmetals are poor conductors
Examples: Oxygen/ Carbon

22. Nonmetal Chemical Properties
Gain electrons.
Form negative ions.

23. Metalloids
Metalloids have some properties of metals and some properties of nonmetals
Metalloids are also called semiconductors because they conduct electric current better than nonmetals but not as well as metals.
Example: Boron and Aluminum

24. Isotopes Different versions of the same element.
Elements can be an Isotope when it has a more or less neutrons.
Same Atomic Number (# of protons)
Different Atomic Number
(# of protons + neutrons).
Because the # of neutrons are different.