1. Chapter 3: Molecules, compounds, and chemical equations

2. Molecules Combining two or more atoms forms a molecule
Combining two or more elements forms a compound
The composition and structure determine the physical and chemical properties of an element or compound
Molecules

3. Chemical formula – tells you the elements and relative atoms in a compound
2 types, molecular and empirical formula
Molecular formula give the actual number of atoms of each element in a compound
H2O2 = two H atoms and two O atoms
Empirical formula – gives the relative atom to atom ratio with whole numbers
H2O2 , greatest common factor is 2 so in empirical form H2O2 = HO
C6H12 = CH2
Chemical formulas

4. Structural formula
A structural formula uses lines to represent covalent bonds between atoms in a molecule

5. Molecular Models
Ball and stick molecular model – each colored ball represents a atom and the sticks represent the bonds between atoms
CH4
Space filling molecular model – size of each atom reflected in size of each sphere
Larger spheres have larger atomic radii
Model gives best 3-D image

6. Element and compound definitions
Atomic elements – elements that exist as single atomic units
Molecular elements – elements that exist as diatomic or polyatomic molecular units
Formula unit – basic unit of an ionic compound
Polyatomic ions – an ion composed of two or more atoms
PO43-

7. Ionic compounds vs Covalent compounds

8. Ionic bonding
Ions: atoms that have a charge due to gain or loss of electrons
Anion: (-) charged atom – gained electron(s)
Cation: (+) charged atom – lost electron(s)
Ionic Bond - a bond formed through the transfer of one or more electrons from one atom or group of atoms to another atom or group of atoms

9. Oxidation state
NaCl
Formula Unit

10. Oxidation state
MgF2

11. Ways to make an ionic compound
Metal + Non-metal
NaCl
Metal + Polyatomic Ion
NaNO3
Polyatomic Ion + Non-metal
NH4Cl
Polyatomic Ion + Polyatomic Ion
NH4NO3
Net charge on compound equal to zero

13. Oxyanions SO42- Sulfate SO32- Sulfite PO43- Phosphate PO33- Phosphite
NO3-
Nitrate
NO2-
Nitrite
ClO4-
Perchlorate
ClO3-
Chlorate
ClO2-
Chlorite
ClO-
Hypochlorite

14. Covalent bond – a bond formed through two atoms sharing electrons
Covalent bonding
or H-H or

15. Ways to make a covalent compound
Covalent compound - two or more nonmetals sharing electrons to make bonds create a covalent compound or molecular compound
nonmetal + nonmetal

16. Nomenclature (naming compounds)

17. Naming ionic compounds
Name the cation by its elemental or polyatomic name
If the metal is a transition metal with a variable charge, use a roman numeral in parentheses for its charge
Next, name the anion and change its ending to “-ide”
If the anion is polyatomic, do not change the ending to “-ide”
NaBr
cation is Na+ = sodium
anion is Br- = bromine  bromide
sodium bromide
FeCO3
Transition metal cation is Fe2+ = iron(II)
Polyatomic anion is CO32- = carbonate
Iron(II) carbonate

18. Iron (III) Chloride
Iron (II) Chloride
FeCl3
FeCl2

19. Hydrated ionic compounds
Hydrates – contain a specific number of water molecules associated with each formula unit
The waters can typically be removed with heating
Ionic compound naming is the same, just add in hydrate and the prefix for the amount of waters

20. Naming covalent compounds
Name the first non-metal by its elemental name
Add a prefix to indicate how many
If only one atom, don’t put mono
4) Name the 2nd non-metal and change its ending to “-ide”
5) Add a prefix to indicate how many
Naming covalent compounds 1
mono 6
hexa 2 di 7
hepta 3
tri 8
octa 4
tetra 9
nona 5
penta 10
deca
CO2
First nonmetal C = carbon
Second nonmetal O = oxygen  oxide
Carbon dioxide

21. Naming acids (acids w/o oxygen)
Acids contain hydrogen atoms that can be donated to other molecules, indicated by being at the front of a chemical formula
Begin the name with “hydro”
Name the anion, but change the ending to “-ic”
Add “acid” on the end
The anion is Br = bromine  bromic
Hydrobromic acid
HBr

22. Naming acids (acids with oxygen)
Begin the name with the anion
If the anion has the ending “-ate,” change this to “-ic acid”
If the anion has the ending “-ite,” change this to “-ous acid”
HNO3
The anion is NO3- = nitrate  nitric
nitric acid

23. EXCEPTION, if in the gas phase, treat like a regular covalent compound for naming with no prefixes
HF(g) = hydrogen fluoride
Naming gas phase acids

24. The Mole

25. 1 dozen eggs = 12 eggs
1 pair of kings = 2 kings
2 dozen eggs = 24 eggs
2 pairs of kings = 2 x 2 kings = 4 kings

26. The Mole 1 mole = 6.022 x 1023 things Avogadro’s number
Abbreviation: “mol”
1 mol = The number of carbon atoms in 12g of C-12

27. Moles to atoms or molecules
1 mole C = x 1023 C atoms
1mol H2O = x1023 H2O molecules
If you have moles of something, you can convert to atoms or molecules of that something
Moles to atoms or molecules

28. Molar mass moles to grams
The mass, in grams, of one mole of any element or compound
Unit = grams/mole = g/mol
Gives us a way to go from grams to moles
1 𝑚𝑜𝑙𝑒 𝐴 𝑥 𝑔𝑟𝑎𝑚𝑠 𝑜𝑓 𝐴

29. Molar Masses for elements and molecules
Use periodic table to figure out Molar mass for each element.
Carbon
1 atom of carbon is amu
1mole of carbon is grams
Molar Mass = g/mol
H2O
Made of 2 hydrogen atoms and 1 oxygen atom
Molar mass of each hydrogen is g/mol
Molar mass of each oxygen is g/mol
2× ×16.00 =𝟏𝟖.𝟎𝟏𝟔 𝒈 𝒎𝒐𝒍
Molar mass of H2O

30. Problems You have 145.9 g Hg. How many moles are in the sample?
b. How many atoms of Hg are in the sample?
2) What is the molar mass for C3H8 (propane)?
3) What is the amount of grams in 3.57 moles of iron(III) chloride (FeCl3)?

31. Composition of compounds
Mass percent – the percentage of mass of an element in a compound (keep units consistent since it is a ratio)
Mass percent of H in H2O
1.008 amu per H atom x 2 H atoms = amu
amu for H2O
Mass percent of element X= mass of element X in 1 mol of compound mass of 1 mol of the compound ×100%
Mass% H= 2.016amu amu ×100%=11.19%H in H 2 O

32. Practice
If you have 55.4 grams of H2O, how many grams of that sample is hydrogen?

33. Chemical formula from empirical data
Decomposing a compound can give you the grams of each of the constituent elements of that compound
The grams can be converted into moles of each element
The whole numbered mole ratio between the elements gives the empirical formula

34. Grams to chemical formula
25.0 g gas decomposes into g of carbon and 6.25 g of hydrogen. What is the chemical formula of the original gas?
18.75𝑔 𝐶 1𝑚𝑜𝑙 𝐶 12.01𝑔 𝐶 = mol C
6.25𝑔 𝐻 1𝑚𝑜𝑙 𝐻 1.008𝑔 𝐻 = mol H
𝐶 𝐻 6.200 =
𝐶 𝐻 =
𝐶 1 𝐻 3.971 =
𝐶 1 𝐻 4 =
C 𝐻 4

35. Mass percent to chemical formula
Given the mass percentages of elements in a compound you can determine in a 100g sample, how much grams of each element would be present
C 60.00%, H 4.48 %, O %
In 100g sample – C 60.00g, H 4.48g, O 35.52g
Once you have the grams, continue the rest of the steps from previous slide

36. Mole ratios of a molecule
The atoms of an element in a molecule can be represented as a mole ratio
2 atoms of H in 1 molecule of H2O
2 mol of H in 1 mol of H2O
2:1 H:O ratio
3 mol of Cl in 1 mol FeCl3
3:1 Cl:Fe ratio
Mole ratio gets you from moles of one element to moles of another element

37. Grams of molecule Moles of molecule Moles of element Grams of element
55.40 grams H2O
Use Molar Mass of H2O
Moles of molecule
3.075 mol H2O
Use Mole ratio between H2O and H
Moles of element
6.150 mol H
Use Molar Mass of H
Grams of element
6.199 grams H

38. Chemical equations H2 (g) + Cl2(g)  2 HCl (g) Reactants Product(s)
Coefficient
Physical State
Subscript
H2 (g) + Cl2(g)  2 HCl (g)
Reactants
Product(s)

39. Law of conservation of Mass
Matter is neither created, nor destroyed, but is merely rearranged
The mass of the reactants must equal the mass of the products
Atoms in the reactants must equal atoms in the products
H2 (g) + Cl2(g)  2 HCl (g)

40. Balancing Chemical Equations
Write the unbalanced equation
Balance the atoms of one element (saving single elements for last)
Choose another element and balance it
Continue until all elements have the same number of atoms on both sides of the equation
Check yourself
__Zn(s) + __HCl(aq)  __H2(g) + __ZnCl2(aq)

41. Problems __ N2(g) + __ H2(g)  __ NH3(g)
__ Fe(s) + __ Cl2(g)  __ FeCl3(s)
__NH3(g) + __O2(g)  __NO(g) + __H2O(g)
__C5H12(l) + __O2(g)  __CO2(g) + __H2O(g)

42. Organic molecules
Living organisms are comprised primarily of organic molecules
Composed of carbon mainly, but also hydrogen, nitrogen, oxygen, and sulfur
Methane, CH4, is the simplest organic molecule

43. Hydrocarbons and functional groups
Hydrocarbons – major class of organic molecules containing carbon and hydrogen
Octane C8H18
Benzene C6H6
Functional group – a characteristic atom or group of atoms
Commonly found attached to hydrocarbons
Organic chemistry focuses on chemistry with organic molecules
Reactions transform one functional group into another, changing the connectivity of the atoms to produce new products
Hydrocarbons and functional groups

44. Functional groups

46. Chapter 3…all done