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DO NOW:1. Make a cover
page in your NB for Chapter 5.
2. Draw a Bohr diagram for sulfur.
3. How many valence electrons does sulfur have?
Chapter 5
Atoms and Bonding
Do Now: Draw a Bohr diagram for sulfur. How many valence electrons does S have?
Sulfur• 16 electrons• 6 valance electrons
16 P16 N
Elements 1 - 201st level = 22nd level = 83rd level = 84th level = 2
Elements 21 – 1121st level = 22nd level = 8
3rd level = 18*4th level = 32*5th level = 32*
*sub-levels exist
Electron Shell
Capacities:
All atoms want to achieve a full octet; which means they have a full outer valence shell
Neon • 10 electrons• 8 valence electrons
Ne
Why Do Valence Electrons Matter?• The valence electrons show WHY certain
elements bond with other elements to form compounds.
S
H H
Sulfur’s 6 valence
electrons WANT 2
more electrons
2 Hydrogen atoms will
make 8 total
Remember, the # of valance electrons matches its family #
Alk
ali M
etal
s
Alk
alin
e E
arth
Met
als
Transition Metals
Bor
on
Fam
ilyC
arbo
n F
amily
Nitr
ogen
Fam
ily
Oxy
gen
Fam
ily
Hal
ogen
sN
oble
G
ases
*Matches 2nd digit groups 13 -18
Electron Dot Diagrams AKA Lewis Structure
• Symbol of an element surrounded by “dots”. • Each dot represents one valence electron.
Electron Dot DiagramsAKA Lewis Structure
• The Element Symbol serves as the representation of the nucleus.
• Dots are added at 12 o’clock, 3 o’clock, 6 o’clock, and 9 o’clock.
Carbon has only 4 electrons in the 2nd energy level so we need only represent those 4
Electron Dot DiagramsAKA Lewis Structure
• Only valence electrons are shown.
• Maximum of 8 dots (electrons)
Electron Dot DiagramsAKA Lewis Structure
Oxygen Group = Valance electrons =
Lewis Structure Practice
Draw Electron Dot Diagrams for Beryllium and Sulfur
Chlorine Group = Valance electrons =
166
177
Beryllium = Group 2 = 2 valance electrons
Sulfur = Group 16 = 6 valance electrons
To Become Stable Atoms… They Bond
Chemical Bonds• Atoms with unfilled valence shells are considered
unstable.• Atoms will try to fill their outer shells by bonding
with other atoms.• The number of valence electrons will determine
how many bonds the atom can form.• A chemical bond is the force that holds the
molecules together
• Two types of bonds we will discuss:– Ionic bonds– Covalent bonds
Understanding chemical formulas:
BaF2
Subscripts: tells how many atoms of that element are in the compound
• refers only to the element preceding it • The subscript 2 in this formula is for the F (fluorine)• Ba (barium) only has one atom (1’s are not written)
Chemical Bonds are represented with Chemical Formulas
3BaF2
Coefficients: refers to each element that follows• Multiply the coefficient with all subscripts• The 3 in this example means there would be
3 Ba (barium) and 3 F2 (a total of 6 fluorine) atoms
Al(NO3)3
Parentheses: The subscript outside the parentheses refers to all the elements inside the parentheses
• Multiply the subscript outside with each subscript inside to get the total number of atoms
• In this example there are: one Al (aluminum), three N (nitrogen), and nine O (oxygen) atoms
Identifying and Counting Atoms in a Chemical Formula
Try It: Count the Atoms in each Chemical Formula
1
1 2
12
6
24
42
1
6
9
6
22
1
4
4
12
21
Try It: Count the Atoms in each Chemical Formula
Back to Bonding…
+1
+20
-3 -2 -1+3+4-4
Valence Electrons Determine Oxidation Numbers
Oxidation Numbers Shows the number of electrons an atom will
gain, lose, or share. Positive (+) or negative (-) number assigned
to an element. Comes from its family number on the Periodic
table1) Metals (Families 1, 2, 13 +1, +2, +3)2) Nonmetals (Families 15, 16, 17 -3, -2, -1)3) Noble Gases (Family 18 0)4) Transition metals have various oxidation numbers
between 1 and 4
+1
+2
0
-3 -2 -1+3+4-4
Atoms that are no longer neutral are called ions
Ions:• An atom or groups of atoms that have lost or
gained electrons• Atom becomes either negatively (-) or
positively (+) charged• Change occurs since the ratio of protons to
electrons is not equal
Ions form from atoms who gain or lose electrons
Cation: positive ion• When an atom loses an electron it becomes positively charged• Ex: Calcium ion = Ca+2
Anion: negative ion• When an atom gains an electron
it becomes negatively charged• Ex: Fluorine ion = F–
(the 1 is inferred)
Oxygen at the Playground
Polyatomic Ions• Ions that stay together
as a group
ammonium nitrate
Poly- ionic name: ammonium nitrate
+
Polyatomic Ions• Ions that stay together
as a group
ammonium nitrate
Poly- ionic name: ammonium nitrate
+
Time to Bond Ions• Each index card represents either a cation (+) or an anion (-)• Any opposite charged ions can bond• Writing the chemical formula and names:
1. Oxidation numbers will become subscript numbers for the opposite element
2. Write both element names, but change the second element ending to “ide”
Oxygen at the Playground
Ionic BondingHow does it work?
• Ionic bonding takes place between metals and non-metals.
• In an ionic bonds :• oppositely charged ions (+) and (-) attract• electrons are transferred• Ex. NaCl (Na +1 Cl -1)
Naming Ionic Compounds• Name of the + ion comes first, and - ion comes second
• Metal + Nonmetal • Monatomic ions: change nonmetal ending to –ide
• Ex: Mg +2 + F -1 becomesMgF2 or Magnesium Fluoride
• Polyatomic ions: change nonmetal ending to –ate or –ite
Ex: NaNO3 = sodium nitrate Mg3(PO4)2 = magnesium phosphate
Do Now1. Draw the Lewis structure for: • Magnesium +2• Iodine -1
2. Write the chemical formula these two ions would create• MgI2 (Magnesium Iodide)
3. What type of bond would these 2 atoms make? • Ionic since Magnesium is Metal and Iodine is a Nonmetal
Mg II
Covalent Bonding• Occurs between two nonmetals• Electrons are shared instead of being transferred
• Both atoms need to gain electrons, so they share the electrons they have.
• Atoms still follow the octet rule• No ionic charges or oxidation numbers
++
++
+
++++-
--
-
-
--
-
OH H
+-
-
Sharingelectron
Sharingelectron
• Electrons move back and forth between the outer energy levels of each atom.
• Each atom has a stable outer energy level some of the time.
• Atoms can share one, two, or three pairs of electrons.
How Covalent Bonding Works
Bonding Animation
BrainPop Bonding
Single Bonds Share 2
Electrons
Double Bonds Share 4 Electrons
Triple Bonds
Share 6 Electrons
+
++
+
+++
+++
-
-
-
-
-
-
-
-+
+-
-
+
+
++
+
+++
+++
-
-
-
-
-
-
-
+
++
+
+++
+++
-
-
-
-
-
-
-
+
++
+
+++
+++
-
-
-
-
-
-
-+
-
+
+
+
+++
+++
-
-
- -
+
++
+
+++
+++
-
-
-
--
-
-
-
+- -
Water (H2O)
Carbon Dioxide (CO2)
Nitrogen (N2)
Naming Covalent Compounds1 mono
2 di
3 tri
4 tetra
5 penta
6 hexa
7 hepta
8 octa
9 nona
10 deca
• Each element gets a “greek prefix”• Prefix refers to # of atoms in the
molecule• Change ending to “ide”
• Ex: N2O4 = dinitrogen tetroxide• The first vowel is often dropped to avoid
the combination of “ao” or “oo”.octaoxide = octoxide
• Exception: drop mono for first elementCO2 = carbon dioxideCO = carbon monoxide
NOW do you find this funny?!
Name these covalent compounds: CCl4 P2O3 IF7
•CCl4 = carbon tetrachloride
• P2O3 = diphosphorus trioxide
• IF7 = iodine heptafluoride
Try This:
Write the covalent compound formula: • Tricarbon pentoxide• Sulfur nonafluorine
• Tricarbon pentoxide = C3O5
• Sulfur nonafluorine = SF9
Try This:
Candy Bonds Activity
Today’s Agenda1. Candy Bonds activity2. Discuss/Correct HW worksheets from last week:
• Elemental Love Story• Naming practice
3. Complete Chapter 5 review worksheet• Check answers in back- flower folder
4. Share Answers to Candy Bonds
* If time: Draw Your Own- plain white paper
1. What type of bond occurs between a metal and a nonmetal? ionic
2. What type of bond occurs between a two nonmetals? Covalent
3. CaF2 Calcium fluoride (*ionic)
4. triphosphorus tetrabromide P3Br4
5. N5O9 Pentanitrogen nonoxide
Name these compounds: • CCl4 = carbon tetrachloride
• P2O3 = diphosphorus trioxide
• IF7 = iodine heptafluoride
Write these compounds: • Tricarbon pentoxide = C3O5
• Sulfur nonafluorine = SF9
Solutions:
What Kinds of Bonds are These?
Ionic BondingSodium Chloride = NaCl = Na+1 + Cl-1