1. More on Atoms Atomic number Molar mass
Atomic Number: number of protons. Determines the type of atom.
Molar mass: mass (in grams) of one mole of atoms. (more on this to come later on)

2. For any atom the number of electrons is always the same as the number of protons.
All atoms are neutral! They have the same number of positives as negatives.
What atom is this?
Helium

3. Atomic Theories Dalton Billiard ball model
Atoms are spherical like billiard balls.
Each atom has it’s own unique properties.
Atoms are indivisible; they are the smallest units of matter.
Atoms can combine in many ways to create a wide variety of chemical compounds
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4. Thomson Raisin Bun Model
Thomson discovers the electron. The electron is 2000X smaller than the smallest atom and has a negative charge. Atoms must contain electrons.
Electrons must be spread-out evenly throughout a positively charged atom like raisins in a bun.
Why would they spread out evenly?
(1856 – 1940)

5. Rutherford Famous Gold Foil Experiment
Alpha particles from radioactive polonium are fired at a thin piece of gold foil (roughly 200 atoms thick)
Most alpha particles pass through the gold undeflected… they should! The experiment is analogous to shooting a cruise missile through some tissue paper!!
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Animation

6. Rutherford’s Model
Atoms have a very small nucleus where (almost) all of the mass is located. Since the nucleus is so small, the alpha particles had a very small chance of actually hitting it.
The nucleus is very dense (1000 trillion times denser than the human body)
The nucleus is made of protons and neutrons. Protons have a positive charge. Neutrons have no charge. Protons and neutrons are about the same mass, roughly 2000 times more massive than electrons.
If a nucleus was the size of an average human being, the bathroom scale would read: 200 quintillion pounds

7. Electrons orbit around the outside of the nucleus at relatively great distance, like planets around the sun. Most of the volume occupied by an atom is empty space!!
If a nucleus was the size of your baby fingernail, the nearest electron would be half a kilometer away!

8. Bohr
Electrons can only exist at certain distances from the nucleus (called orbits, shells, or energy levels)
The maximum number of electrons for the 1st energy level is two. Eight electrons is the maximum number for the 2nd and 3rd energy levels.
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9. Bohr Diagrams Energy Level Diagrams Notice the filling order
What atom is being represented?
sodium

10. Isotopes carbon-12 carbon-14 Mass number (protons + neutrons)
Atomic Number
(protons)
How many neutrons does carbon-14 have?
carbon-14
Eight neutrons

11. Ions
If an atom gains or loses electrons it forms an ion. The number of protons and electrons are not equal for ions.
An ion has a (+/-) charge. The charge is really the net charge.
If you add up all of the positive and negative charges, you get the net charge.
and gives you no net charge
+ + + and gives you a net charge of 1+
What does and give you ?
a net charge of 1 -
Note: the number of neutrons has no affect on the net charge

12. Energy Level Diagrams for Ions
The number of protons never changes when an atom becomes an ion.
Decide on the correct number of electrons by looking at the charge on the ion.
Compare the total number of electrons and protons in each example
Notice that non-metals gain electrons to form negative ions, and metals lose electrons to form positive ions.

13. Ions form so that atoms can become more stable.
Stability is achieved when there is a full valence shell (outermost shell). Valence electrons are the outer most electrons.
If the first shell is the valence shell, then stability is achieved by having two valence electrons. If any other shell is the valence shell, then stability is achieved using eight electrons (Octet Rule).
Noble gases already have full valence shells. Do Noble gases form ions?
NO!

14. Ions form to have the same electron configurations as the nearest noble gas

15. Naming Ions For now just remember two simple rules:
All ions end with the word “ion”
EG: is called a sodium ion _
Non-metal ions (negative ions) end in “ide”
EG:
Is called a Chloride ion

16. Periodic Table
Groups go down
Non-metals: Elements to the right of the blue staircase.
Periods go across
The Staircase
Metals: Elements to the right of the blue staircase.

17. Periodic Law: When elements are placed in order of increasing atomic number in periods (horizontal rows) , groups form (vertical columns). The members of each group share similar chemical properties.
Group 1: Alkali Metals
Group 2: Alkaline Earth Metals
Group 17: Halogens
Group 18: Noble Gases

18. Groups 1, 2 and 13 to 18 are called the Representative Elements.
This is because these groups best obey the periodic law. Here are some examples:
Group 1(Alkali Metals): All react violently with water to produce a strong base and hydrogen gas.
Group 2 (Alkaline Earth Metals): React in air to produce dull outer coatings of metal oxide.

19. Representative elements cont’:
Group 17 (Halogens): All exist naturally as diatomic molecules.
Group 18 (Noble gases): All are unreactive.

20. Other Regions of the Periodic table
Transition Metals: These are all the elements from group 1 to the staircase.
Lanthanide Series: Part of period 6 starting at the short blue line after Lanthanum.
Actinide Series: Part of period 7 starting at the short blue line after actinium.

22. Empirical Properties of Metals and Nonmetals
Lustrous
Ductile
Malleable
Conduct electricity
Nonmetals
Dull
Brittle
Nonconductors