1) Atoms are made of protons, neutrons and electrons. Electrons orbit the nucleus in shells. Atoms bond by gaining, losing or sharing electrons to fill their outer shells. 2) The periodic table arranges elements based on their atomic structure. Elements are classified by their valence - extra or missing electrons in the outer shell. 3) Compounds form when elements bond by exchanging electrons to achieve stable full outer shells. Water, carbon dioxide, ammonia and table salt are examples of common compounds formed through electron bonding.

1. Chemistry Theory for
Kaya + Zoey

2. Atoms and Electron Orbits
basis of chemistry

3. Proton, Electron, Neutron
z Proton
+
Neutron
0
Electron
-

4. Atomic Structure
z
• Protons and neutrons are in a central nucleus
• Electrons revolve around the nucleus
• The number of electrons and protons are the same
• The number of neutrons can differ but chemistry is the same
• The electrons revolve in several orbits
• The outer orbit is the key one for chemistry
• The first orbit can hold up to 2 electrons
• The second and third orbit can hold up to 8 electrons
• The fourth and fifth orbit can hold 18 electrons
• Atoms want to have a full outer orbit
• They can do this by taking or giving away electrons from other atoms

5. Atoms are called Elements
Here are some examples
Chemistry depends on electrons in outer orbit

6. z
Hydrogen Symbol = H
Hydrogen is the lightest gas. The sun is mostly hydrogen
Missing 1 electron to completely fill the orbit
Hydrogen wants to give away 1 electron +1

7. Helium Atom = He
Helium is a light gas used in balloons
z
No missing electrons. The orbit is full
Helium does not need to give or take any electrons

8. Oxygen = O
Oxygen is the gas we breathe in
z
Two missing electrons. The orbit can hold up to 8 electrons
Oxygen want to take two electrons. (-2)

9. Carbon = C
Carbon is the basis of all living things on Earth
z
Four missing electrons. The orbit can hold up to 8 electrons
Carbon can give or take 4 electrons (+4 or -4)

10. Combining Element Atoms produces Compounds
Compounds are called Molecules
Here is the most important example

11. Water Molecule = 2 hydrogens and 1 oxygen = H2O
z
2 Hydrogens gives 1 electron each to complete oxygen’s outer orbit

12. Diagrams for Water Molecule H2O
Water is necessary for life on Earth to exist
z
Hydrogen
Hydrogen
Oxygen
H H
O
Simplified diagram

13. z
H H
HH
Some Elements can also form Molecules
Oxygen (-2) often forms molecule of O2
Each Oxygen has 2 edges
Hydrogen (+1) often forms molecule of H2
Each Hydrogen has 1 edge
O O
OO

14. Periodic Table
atoms arranged based on outer electron orbits

15. Periodic Table based on electrons in outer orbit
z

16. Common Elements
z
1 H = Hydrogen (+1)
2 He = Helium (0)
3 LI = Lithium (+1)
4 Be = Beryllium (+2)
5. B = Boron (+3)
6. C = Carbon (+4 or -4)
7. N = Nitrogen (-3)
8. O = Oxygen (-2)
9 Fl = Fluorine (-1)
10 Ne = Neon (0)
11 Na = Sodium (+1)
12 Mg = Magnesium (+2)
13 Al = Aluminum (+3)
14 Si = Silicon (+4 or -4)
15 P = Phosphorus (-3)
16 S = Sulphur (-2)
17 Cl = Chlorine (-1)
18 Ar = Argon (0)
19 K = Potassium (+1)
20 Ca = Calcium (+2)
21 Sc = Scandium (+3)
22 Ti = Titanium (+4)
23 V = Vanadium (+5)
24 Cr = Chromium (+6)
25 Mn = Manganese (+7)
26 Fe = Iron (+8)
27 Co = Cobalt (+9 or -9)
28 Ni = Nickel (-8)
29 Cu = Copper(-7)
30 Zn = Zinc (-6)
The numbers in parentheses are extra electrons (+) or missing electrons (-)
This number is called the Valence of the element

17. Periodic Table is based on Electrons in Orbits
z
1 electron
in outer orbit 2 electrons
in outer orbit
3 electrons
in outer orbit
4 electrons missing
in outer orbit
3 electrons missing
in outer orbit
2 electrons missing
in outer orbit
0 electrons missing
in outer orbit
1 electron missing
in outer orbit

18. Combining Atoms produces Compounds
The next few slides have some examples
Note that each atom has links = | Valence |
|+2| = 2 and | -2 | = 2
|n| is called the absolute value of n

19. Diagrams for Water Molecule H2O
Valences: H = +1 and O = -2
Hydrogens have 1 link and Oxygen has 2 links
z
Hydrogen
Hydrogen
Oxygen
H H
O
Simplified diagram

20. Carbon Dioxide Molecule CO2
The gas that we breathe out
The major cause of global warming by trapping heat
z
C
O
O
Valences: Carbon (C) is +4 and Oxygen (O) is -2
Carbon has 4 links and Oxygen has 2 links
O OC

21. Ammonia Molecule NH3
Ammonia is a poisonous gas
Nitrogen is the most common gas in air
z
Hydrogen
Hydrogen
Nitrogen
Hydrogen
H H
N
H
Nitrogen (N) is -3 and Hydrogen (H) is +1
Valences: Nitrogen has 3 links and Hydrogens have 1 link

22. Salt Molecule NaCl
Sodium (Na ,+1) burns your skin badly
Chlorine (Cl, -1) is a poisonous gas
Together NaCl is table salt
z
Na Cl
Na Cl
Valences : Na has 1 link and Cl has 1 link

23. Isotopes

24. Isotopes are elements with the same number of protons but different number of neutrons
All isotopes have the same chemistry
The weight of an atom is the sum of the number of protons and neutrons. Electrons are very light.
For example, Hydrogen has 3 isotopes
Ordinary Hydrogen with 1 proton and 0 neutrons is Hydrogen1
Deuterium with 1 proton and 1 neutron Hydrogen 2
Tritium with 1 proton and 2 neutrons Hydrogen 3
Isotopes

25. Famous Isotopes
Isotopes are often radioactive
Carbon has several isotopes
Carbon 14 is radioactive and is used to date organic specimens
Uranium (U) is the heaviest element in nature with 92 protons
U238 (146 neutrons) is the most common isotope in nature
U235 (142 neutrons) is used in atom bombs

26. Carbon Chemistry Basis of Life
called Organic Compounds

27. Methane CH4
Methane is a poisonous gas emitted by volcanoes
z
C HH
H
H
Carbon (C) is -4 and Hydrogen (H) is +1
Valences: Carbon has 4 links and Hydrogen has 1 link
H
H
C
H
H

28. Ethane C2H6
Ethane is used in making plastics
z
Carbon (C) is -4 and Hydrogen (H) is +1
Valences: Carbons have 4 links and Hydrogens have 1 link
C C
H
H
H H
H
H

29. Methane, Ethane, Propane
Propane is the basis of gasoline
z

30. Drinking Methyl Alcohol can kill you
Note H has 1 link, C has 4 links, O has 2 links
z
Note that Methyl Alcohol is Methane with an H replaced with a O-H

31. Drinking Ethyl Alcohol makes you drunk
Note H has 1 link, C has 4 links, O has 2 links
z
Note that Ethyl Alcohol is Methane with an H replaced with a O-H

32. Urea was the first body chemical made in the Lab
Note that O has 2 links, C has 4 links, N has 3 links, H has 1 link
z

33. Benzene is used make plastics and gasoline
Note that every C atom has 4 links
and every H atom has 1 link
z