1. These models are easy to draw – if you follow the steps!
What are Bohr Models?
Neils Bohr devised a method for drawing models to represent the atoms nucleus and their electron arrangement because the atoms are too small to see.
These models are easy to draw – if you follow the steps!

2. F Drawing Bohr Models 9 Step 1:
Determine the number of protons, electrons and neutrons for each atom’s element.
Fluorine = F F
18.98
Fluorine 9
(Atomic Number) #Protons = 9
(Atomic Number) #Electrons = 9
# Neutrons = atomic mass – atomic #
# Neutrons = 19 – 9=10

3. Drawing Bohr Models - Continued
Step 2:
Draw a nucleus inserting the # of protons and # of neutrons that are inside.
# Electrons = 9
# Protons = 9
# Neutrons = 10
Fluorine = F
N =
P = 10 9

4. Drawing Bohr Models - Continued
Step 3:
Determine the number of electron rings to draw around the nucleus by what row it is in on the Periodic Table.
# of rings = row number
Fluorine is in row #2
so, I need to draw 2 rings around the nucleus.
N =
P = 10 9

5. Drawing Bohr Models - Continued
Step 4:
Place the electrons on the correct energy ring – filling each to capacity.
Energy Levels are Identified as: 3 4
N =
P = 10 9
1st Level –holds 2e-
2nd Level –holds 8e- 5 2 1
3rd Level –holds 8e- 6 9
Remember we need to have 9 electrons total for fluorine! 8 7

6. Complete Bohr Model P = 9 N = 10 Fluorine = F # Protons = 92 3 4 5 6 7 8
# Protons = 9
# Electrons = 9
# Neutrons = 10 2
Max # of Electrons
Energy Level 8 1 3

7. Happy / Stable Elements
Elements that have a full outer ring of electrons are called “happy” atoms. 2
Max # of Electrons
Energy Level 8 1 3
Meaning that – that ring can’t hold any more electrons.
Page Down: In making a diagram of an element scientists used to use a model called the Bohr Model. Although it does not completely describe the structure of an atom, it is a useful tool for understanding the interactions of matter. First you would write down the # of protons and neutrons the atom has.
Page Down: First energy level - can hold up to 2 electrons. Page down
Page Down: Second energy level - can hold up to 8 electrons.
Page Down: Because the atoms are spinning around the nucleus it is important to put the out of each other’s path. The first two are paired. The next three are distributed around the energy level one at a time. The next three are paired with the previous three. Teacher Note: The rationale for teaching this is to help them understand the Lewis Dot diagrams later.
Page Down: Third energy level - Similar to the 2nd level… however in reality the students will learn more about this level in chemistry.
Page down.
Make sure that the students have copied this slide.
So, if the 2nd ring has 7 electrons in its outer ring – it is still hungry for the 8th electron – needing it to be “happy.”

8. Happy / Stable Elements
The last ring or outer shell of the atom is called the . . .
Energy Level
Remember the # of rings that you drew in the Bohr model is equal to the Row number that the element is in on the Periodic Table. 16 S
32.07 17 Cl
35.45 18 Ar
39.95 10 Ne
20.18 9 F
19.00 13 Al
26.98 14 Si
28.09 15 P
30.97 5 B
10.81 6 C
12.01 7 N
14.01 8 O
16.00 2 He
4.0
Fluorine = Row 2
Fluorine Energy Level = 2

9. Happy / Stable Elements
The number of electrons in that last ring or outer shell is called the . . .
Valence Electrons 16 S
32.07 17 Cl
35.45 18 Ar
39.95 10 Ne
20.18 9 F
19.00 13 Al
26.98 14 Si
28.09 15 P
30.97 5 B
10.81 6 C
12.01 7 N
14.01 8 O
16.00 2 He
4.0
Fluorine = Column VIIA
Fluorine Valence # = 7

10. F What are Lewis Dot Diagrams?
G.N. Lewis, an American chemist, developed this shorthand system using only the element’s symbol and dots.
The symbol represents the element’s nucleus. F
The dots represent the #of valence electrons of that element.
Fluorine Valence # = 7 or 7 electrons in outside shell

11. Drawing Lewis Dot Diagrams
14.01
Nitrogen 7 Cl
35.45
Chlorine 17
Using just your periodic table, draw
Lewis Dot Diagrams for each of the
above elements.

12. Bonding and Molecules
Energy levels-where electrons are found in the electron cloud
Valence electrons
outermost region of electron cloud
Maximum number is 8, except at first level only holds 2
Octet rule-atoms share or transfer to form bonds and become stable max at 8

13. Chemical Bond Chemical bond
force that holds together the atoms in a substance
By losing, gaining or sharing electrons atoms become stable and will make a bond

14. Ions Atoms that have a charge
By looking at the outer energy level you can tell what charge the ion has on it
Written with a superscript number above
Na+1, Cl-1, P-3, Mg +2

15. Oxidation Number Number we assign from the ion charge
Positive or negative number
Tells how many electrons will be gained, lost or shared in a bond
Remember
losing electrons causes a (+ #)
gaining electrons cause a (- #)

16. Types of Bonding Ionic Bond Gaining or losing electrons
Usually formed by bonding between METAL and NONMETAL
Force of attraction between the opposite charges of the ions
2. Covalent Bond
Sharing electrons
2 NONMETALS

17. Diatomic Molecules Covalent bonds
Molecule that has 2 atoms of the same element
Br2, I2, N2, Cl2, H2, O2, F2
Electronegativity
Attraction an atom has for the shared pair of electrons in a covalent bond
Need to gain 1 or 2 electrons-high ELN
Need to lose 1 or 2 electrons- low ELN

18. Chemical Formulas Chemical shorthand for a compound
Subscript # tells how many atoms of that element
Tells what elements it contains and ratio of atoms
NaCl=1 atom sodium, 1 atom chlorine
H2O=2 atoms hydrogen, 1 atom oxygen
Fe2O3=2 atoms iron, 3 atoms oxygen
Ca(OH)2=1 calcium, 2 oxygen, 2 hydrogen

19. Independent Practice
Counting Atoms

20. MgCl2 Writing Chemical Formulas
The ratios in which compounds are formed are called their chemical formula.

21. Where do the subscripts come from? it comes from the oxidation number.
That one is easy –
it comes from the oxidation number.
Remember that the oxidation number tells us how many electrons each particular element has extra to give away or how many it needs to become happy.
MgCl2

22. Remember the Oxidation Numbers?
# needing / wants to get find more electrons
# extra / wants to get rid of the electrons 1+ 2+ 3+ 4 3- 2- 1-
Oxidation Number Varies
When you combine atoms, you use the oxidation numbers to help you figure out the ratio.

23. Let’s take a look now at the rules to writing the compounds…

24. Rules for Writing Ionic Compounds
Write down the symbol and the oxidation # for each element-metal then nonmetal
Mg+2
Cl-1
Criss cross the oxidation number to get the correct subscript.
Mg+2
Cl-1 1 2
3. Leave off the (+ or -) signs

25. Rules for Writing Ionic Formulas
Drop out the “1’s”
Cancel out the numbers if they are the same
MgCl2

26. Let’s look at some examples…..

27. Mg+2 O-2 MgO Fe+3 O-2 Fe2O3 GROUP PRACTICE 2 =
2’s here cancel each other out – that way 1 is shown as the subscript.
Fe+3
O-2
Fe2O3 2 3
These subscripts can’t cancel – so they just switch & lower.

28. Fill in the the chart on your paper.
Independent Practice
Fill in the the chart on your paper.

29. Now that we know how to write the formulas for the compounds – let’s name them.

30. Naming Binary Ionic Compounds Binary (meaning 2 types of atoms)
Metal & Non-Metal
Example: KBr
Write the name of the metal first.
2. Write the name of the nonmetal changing the ending to “ide.”
Potassium
Bromine
Bromide

31. Fill in the the chart on your paper.
Independent Practice
Fill in the the chart on your paper.

32. Naming Binary Covalent Compounds
Non-Metal & Non-Metal
Example: CO2
1. Name the first non-metal farthest to the LEFT.
Left First
Carbon
Right Second
Oxide
Write the name of the second non-metal farthest to the
RIGHT and change the ending to “-ide.”
Leaving a space between them
Carbon Oxide

33. CO2 Carbon Oxide Non-Metal & Non-Metal – Continued Carbon oxide di
Insert the correct prefix in front of the second (2nd)
non-metal to indicate the number of atoms present.
Prefixes include:
1 – mono 2 – di 3 – tri
4 – tetra 5 – penta 7 - septa
Carbon
oxide di
Question: How do you use carbon dioxide everyday?

34. Independent Practice
Fill in the blanks.

35. Covalent Compounds continued
If attached to H+1 it is an ACID
Will not have prefixes
Examples:
HCl=hydrochloric acid
H2SO4=sulfuric acid
H3PO4=phosphoric acid

36. Naming Binary Compounds Transition Metal & Non-Metal
Example: CuCl
1. Write the name of the transition metal first.
2. Write the name of the nonmetal changing the ending to “ide.”
3. Reverse criss cross to determine the Roman numeral because chlorine is -1 and there are no subscript numbers then copper must be +1
4. The first element name gets a Roman numeral after it
based on the oxidation number.
Copper
(I)
Chloride
Chlorine
because the oxidation of Copper is +1 in this case.

37. Independent Practice
Fill in the blanks.

38. Special Transition Metals
Some transition metals have more than one oxidation number and a special name.
Fe+2 ferrous Hg +1 mercurous
Fe+3 ferric Hg +2 mercuric
Cu+1 cuprous Sn+2 stannous
Cu+2 cupric Sn+4 stannic

39. What are Polyatomic Ions?
We have been working with monoatomic ions. These are single elements. Na +1, N-3, Br-1
Polyatomic Ions are covalent bonded groups of atoms and act as a unit.
They usually stay together and don’t separate.
(PO4) – most of the time, you see them with ( ) marks around them.

40. Polyatomic Ion & Charges
You will need to recognize the name & formula of these.

41. Writing Formulas Containing Polyatomic Ions
Write down the symbol and the oxidation # for each element / polyatomic ion
Criss cross and put the #s in lowest terms if necessary. (Reduce)
3. Write the formula for the compound.
Mg+2
PO4-3
Li+1
SO4-2 2 3 2 1
Mg3(PO4)2
Li2SO4
Note the ( ) on multiple polyatomic ions.

42. Independent Practice
Fill in the blanks.

43. Naming Compounds w/polyatomic ions
Example: K2 SO4
1. Write the name of the metal first.
2. Write the name of the polyatomic nonmetal from the chart.
Potassium
Sulfate

44. Naming Compounds that start w/polyatomic ion
Example: NH4Cl
1. Write the name of the polyatomic ion first.
2. Write the name of the nonmetal changing the ending to “ide.”
Ammonium
Chloride

45. Independent Practice
Fill in the blanks.

46. Formula Mass Calculate the formula mass for the following H2SO4 KNO4
4 K2SO4
2 Ca3(PO4)2