Homogeneous matter has the same appearance, composition, and properties throughout.
Heterogeneous matter has visibly different phases which can be seen, or properties that vary through the substance. 2
Classification of Matter
3
Classification of Matter
A mixture is two or more pure substances that can be separated by physical changes or method.
Pure substances have a distinct set of physical and chemical properties and cannot be separated by physical changes.
4
Pure Substance
A compound is a pure substance that can be decomposed by a chemical change or method into two or more elements. Two or more elements together.
An element is a pure substance with its own set of physical and chemical properties that cannot be decomposed into simpler substances. Simplest form of matter. (Chapter One) 5
Classify
Water
Aluminum foil
Air
Oxygen
Cake 6
What is in your coffee?
Why do we drink coffee? How does it work? The active ingredient caffeine interferes with biochemical reactions in the body.
7
How does coffee work?
The activity releases adrenaline; which activates the release of dopamine
8
Why do Atoms Combine?
To mimic or acquire the stability of the noble gases.
Stability is due to number of valence electrons noble gases contain.
Atoms of elements will accept or give away electrons to become more stable. 9
Reactivity of Elements
What will elements do to have the same number of electrons as the noble gases?
What will Sodium do? (b)
11p+ 11 e-
Na
Æ
(c)
11p+ 10 e-
Na+ + e10
Reactivity of Elements
What will potassium do?
19
p+
19
e-
Potassium Atom
In
general:
M1A
- 1e-
Argon has 18 e-
19 p+
18 e-
Potassium Ion (K+) Cation
Æ M1A+1 + 1e11
Formation of Ions
What about Magnesium? What’s the closest noble gas to magnesium? Neon has 10 e-
12 p+
12
e-
-2e12 p+
10 e-
Magnesium Ion (Mg+2)
Magnesium Atom
Cation
M2A Æ M2A+2 + 2e12
Where do the electrons go?
Must find an element that might need some extra electrons. What will bromine do? Who’s the closest noble gas? Krypton has 36 e-
35 p+
35
+ 1e-
e-
35 p+
36 e-
Bromide Ion (Br-)
Bromine Atom
Anion
X7A + 1e- Æ X7A-1 13
Formation of Monatomic Ions Group 1A-3A Metals Group 5A-7A Nonmetals
Na → Na+ + 1 e-
N + 3 e- → N3-
Ca → Ca2+ + 2 e-
S + 2 e- → S2-
Al → Al3+ + 3 e-
F +
Cations Lose or give away electrons
e- → F Anions Accept electrons
Cation + Anion = Ionic Compound 14
Ionic Compounds
Form when electrons are transferred from one element to the other.
Metals – give away electrons and become cations
Nonmetals – accept electrons from metals
15
To write the formula of the ionic compound first predict the charge of each element and then write the neutral formula. Positive has to cancel negative. Practice the following:
a) Ions that come from elements sodium and fluorine
b) Ions that come from elements calcium and bromine
c) Ions that come from elements magnesium and nitrogen
16
Naming Ionic Compounds
Write the name of the cation (metal ion). The name of a cation is the same as the metal name.
Write the name of the anion (nonmetal ion) by changing the ending of the element name to ide. Ca2+ = calcium ion S2- = sulfide ion
Name the previous exercise
17
Transition Metals
As metals they give away electrons. They give away a variable number of electrons from:
1e- to 7e-
For most transition metals the highest number of electrons corresponds to the roman numeral in the column. Most common charges are +2 and +3. Get the charge of the metal from the anion to which it’s combine. 18
Exceptions to the Variable Charges
Three exceptions: Ag
gives away 1e- to form Ag+
Zn
gives away 2e- to form Zn+2
Cd
gives away 2e- to form Cd+2
19
Predict the Correct Chemical Formula for:
Co+3 and sulfide
A) CoS
Cadmium and iodide
A) CdI
b) Co2S
b) CdI2
c) Co3 S2
c) Cd2I
d) Co2 S3
c) Cd2I3
20
Naming Ionic Compounds of Transition Metals
Add the charge of the metal as a Roman numeral in parenthesis. cobalt (II) fluoride. What is the name of FeCl2
Mn2O3
a) Magnesium (II) oxide c) Manganese (III) oxide
b) manganese (II) oxide d) manganese oxide 21
Polyatomic Ions
Group of elements that together have a charge.
22
A few more polyatomic ions
Group of elements that together have a charge.
ClO4- Perchlorate Æ One more O: Charge is the same ClO3- Chlorate “Parent” polyatomic ion (looks like Nitrate) ClO2- Chlorite Æ One less O: Charge is the same ClO- or OCl- ---> Hypochlorite One less O: Charge is the same
23
What’s the Chemical Formula?
Boron hydroxide
Palladium (IV) hypochlorite
Ammonium sulfite
24
From Formulas to Names
Fe2(SO4)3
a. iron (II) sulfate
Pb(NO3)4
b. iron (III) sulfite
c) iron sulfate
d. iron (III) sulfate
25
Properties of Ionic Compounds •Solids at Room Temperature •High Melting and Boiling Point •When dissolved in water the solutions are conductors of electricity. •Strongest type of intermolecular force: ion-ion
26
Sharing of Electrons
27
Lewis Dot Structures Valence electrons are represented as dots around the symbol of an element. Electrons are not paired unless necessary
Noble gases have eight valence electrons in their outer shell or energy level.
28
The Octet Rule
Atoms want to have eight electrons in the outer shell, as the stable noble gases.
Atoms may gain, lose or share electrons to obtain eight electrons in the outer shell.
Hydrogen and helium can hold only two electrons in their outer shell.
What is the Lewis structure of fluoride?
29
Covalent Compounds
Share electrons to complete their octet.
Formed by nonmetals interacting or attracted to other nonmetals.
The bond forms by overlap of electron clouds.
Represented as a tug-of-war or holding hands.
Simplest representation is a molecule 30
Covalent Compounds H
Î
H
+
F
+
F
Î
O
+
O
Æ
Reason for the existence of diatomic elements 31
Covalent Bonds
Single Covalent Bond - Sharing of two electrons between two atoms.
Double Bond – Sharing of four electrons between two atoms.
Triple Bond – Sharing of six electrons between two atoms.
32
Number of Covalent Bonds Formed by Nonmetal Atoms
Lewis Dot Structure
Number of Bonds:
4
3
2
1
0
Lone Pair or Nonbonding Electrons – not used in bond 33
Naming Covalent Compounds
Opposite to ionic compounds nonmetals combine to other nonmetals in different proportions.
CO
vs.
CO2
carbon monoxide vs. carbon dioxide
We need prefixes to indicate how many.
34
Naming Covalent Compounds 1 2 3 4 5
mono di tri tetra penta
6 7 8 9 10
hexa hepta octa nona deca
Only for covalent compounds 35
Let’s Try It! Name each binary molecule a) BF3 b) SCl6 c) CoI2 d) P2O5 36
Lewis Structure What molecules look like in Three-Dimensions
Lewis Structure Drawings
Calculate total number of valence electrons. Connect all atoms to the central atom with single bonds. Subtract valence electrons used (2e- /bond) Complete the octet of outside atoms using lone pairs. If left over electrons available, give to central atom. Check that central atom has a complete octet. If less than eight electrons, take two electrons from outside atom and form a double bond.
Lewis Structure
SO2
SO3-2
PCl5
Formal Charges For each atom F. C. = Column # - (# dots + # bonds)
Expanded octet – Larger atoms in period 3 or below can accommodate more than 8 e-
Lewis Structure SO3-2
PCl5
GRAMS AND MOLES
Mass of Chemical Compounds
Formula or Molecular Weight is the sum of the atomic mass of the elements in the formula. Sodium chloride (NaCl) has a formula weight of 58.5 amu Na+
Cl-
NaCl
22.99 amu
35.45 amu
58.44 amu
amu = atomic mass unit is the mass of an atom
43
Avogadro’s Number of Molecules
1 molecule is at microscopic level
1 mole is at macroscopic level
1 mole = 6.02 x 1023 atoms or molecules
1 mole is the most important unit of measurement for chemists because the relation exist within chemical formulas or chemical equations. 44
Molar Mass
The mass (in grams) of one mole (6.02 x1023 ) of substance.
Molar mass can be used to convert between the number of moles of a particular compound and its mass.
6.02x1023 Atoms or Molecules
1 mole
Molar Mass in grams
What is the molar mass of silver nitrate?
45
How many moles of silver nitrate are used if 85.7 grams are used in an experiment?
A) 0.505 mol b) 1.98 mol c) 0.557 mol d) 0.331 mol How many molecules of silver nitrate are in the above question?
46
Practice What is the mass of 0.315 moles of sodium bicarbonate?
How many moles of sodium bicarbonate are in 24.54 g of it?
a) 2061 mol
b) 0.092 mol
c) 0.292 mol
d) 1 mol
How many molecules of sodium bicarbonate are contained in 24.54g?
