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Chemical Bonds, Names and Formulas
Unit # 6
Big Ideas
OBJECTIVES:– Distinguish between ionic and
molecular compounds.– Distinguish between ionic, covalent
and metallic bonds– Define cation and anion, and relate
them to metal and nonmetal.– Name molecules and compounds
What is a bond? The valence electron of one atom is
attracted to the nucleus of another atom Reasons Why?
– Mutual attraction– To achieve a full valence shell– To have lower Kinetic Energy
Covalent Bonds When a pair of electrons are “shared”
between two atoms This will occur between atoms that have
similar electronegativity values Non-metal bonded to non-metal
Covalent Bonds Single bond – one pair of electrons are
shared (2 electrons) Double bond – two pairs of electrons
are shared (4 electrons) Triple bond – three pairs of electrons
are shared (6 electrons)
Ionic Bonds An unequal sharing of a pair of
electrons between atoms Between a metal and a non-metal We usually say “ the metal will give up
the electron and the non-metal will take the electron
Atoms that have a electronegativity difference higher than 1.7
Metallic Bonds Bonds between 2 metals Both metals will give up electrons and
then share the “sea of electrons”
Determine the bond typeH2OHClNaClKCrKBr
Determine the bond typeH2O covalentHClcovalentNaCl ionicKCrmetallicKBr Ionic
Let’s Review some old concepts to tie this
together
Atoms and ions Atoms are electrically neutral. Same number of protons and electrons. Ions are atoms, or groups of atoms,
with a charge (positive or negative) Different numbers of protons and
electrons. Only electrons can move. Gain or lose electrons.
Anion A negative ion. Has gained electrons. Nonmetals can gain electrons. Charge is written as a superscript on
the right.
F1-Has gained one electron (-ide is new ending= fluoride)
O2- Gained two electrons (oxide)
Cations Positive ions. Formed by losing electrons. More protons than electrons. Metals can lose electrons
K1+ Has lost one electron (no name change for positive ions)
Ca2+ Has lost two electrons
Back to New Material
Now let’s bond the old material to the new material
Two types of Compounds
Ionic and molecular
Ionic Compounds Ionic compounds- from joining
metal and nonmetal - they are electrically neutral
Metal and polyatomic ion
Ionic Bonds
Ionic Compounds This formula represents not a
molecule, but a formula unit The smallest whole number ratio of
atoms in an ionic compound. Ions surround each other so you
can’t say which is hooked to which.
Molecules and Molecular Compounds
Molecular compounds Made of molecules. Made by joining nonmetal atoms
together into molecules. Covalent bonds
Molecules and Molecular Compounds
Molecule- smallest electrically neutral unit, still has properties of the substance
Made from only nonmetals Can be from one element- O2
Can make a compound- CO2
Two Types of Compounds
Smallest piece
Bond Type
State
Types of elements
Formula Unit Molecule
Metal and Nonmetal
Nonmetals
solidSolid, liquid or gas
Ionic Covalent
Ionic Molecular
Chemical Formulas Shows the kind and number of
atoms in the smallest piece of a substance.
Molecular formula- number and kinds of atoms in a molecule.
CO2
C6H12O6
Chemical Formulas More than one atom? –use a
subscript (H2O) There are 7 diatomic elements Hydrogen (H2), Nitrogen (N2),
Oxygen (O2), Fluorine (F2), Chlorine (Cl2), Bromine (Br2), and Iodine (I2)
Remember: “Br I N Cl H O F”
Charges on ions Elements in the same group have
similar properties. Including the charge when they are
ions Remember Group 1 forms +1 ions
2+
1+
3+ 3- 2- 1-
What about the others? Many transition metals have more
than one common ionic charge We use roman numerals in naming
More Big ideas OBJECTIVES:
– Name ions based on their oxidation state
– Define a polyatomic ion, and give the names and formulas of the most common polyatomic ions.
Naming ions Two methods if more than one
charge is possible:
–1. Stock system – uses roman numerals in parenthesis to indicate the numerical value
–2. Classical method – uses root word with suffixes (-ous, -ic)
• Does not give true value
Naming ions We will use the Stock system. Cation- if the charge is always the
same (Group A) just write the name of the metal.
Transition metals can have more than one type of charge.
Indicate the charge with roman numerals in parenthesis
Name these Na1+ Ca2+ Al3+ Fe3+ Fe2+ Pb2+ Li1+
Write Formulas for these Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion
Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluorine
Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluorin
Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluori
Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluor
Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluori
Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluorid
Naming Anions Anions are always the same charge Change the element ending to – ide F1- Fluoride
Name these Cl1- N3- Br1- O2-
Ga3+
Write these Sulfide ion iodide ion phosphide ion Strontium ion
Exceptions: Some of the transition metals have
only one ionic charge:
–Do not use roman numerals for these:
–Silver is always 1+ (Ag1+)
–Cadmium and Zinc are always 2+ (Cd2+ and Zn2+)
Polyatomic ions Groups of atoms that stay together and
have a charge.
Acetate C2H3O21-
Nitrate NO31-
Nitrite NO21-
Hydroxide OH1- and Cyanide CN1- Permanganate MnO4
1-
Polyatomic ions Sulfate SO4
2-
Sulfite SO32-
Carbonate CO32-
Chromate CrO42-
Dichromate Cr2O7
2-
Phosphate PO43-
Phosphite PO33-
Ammonium NH41+
Big Idea
OBJECTIVES:– Apply the rules for naming and writing
formulas for binary ionic and ternary ionic compounds.
Naming Binary Ionic Compounds Binary Compounds - 2 elements. Ionic - a cation and an anion. To write the names, just name the two
ions. Easy with Representative elements
(which are Group A elements) NaCl = Na1+ Cl1- = sodium chloride
MgBr2 = Mg2+ Br1- = magnesium bromide
Naming Binary Ionic Compounds The problem comes with the
transition metals. Need to figure out their charges. The compound must be neutral. same number of + and – charges. Use the anion to determine the
charge on the positive ion.
Naming Binary Ionic Compounds Write the name of CuO Need the charge of Cu O is 2- copper must be 2+ Copper (II) oxide Name CoCl3 Cl is 1- and there are three of them = 3- Co must be 3+ Cobalt (III) chloride
Naming Binary Ionic Compounds Write the name of Cu2S.
Since S is 2-, the Cu2 must be 2+, so each one is 1+.
copper (I) sulfide Fe2O3 Each O is 2- 3 x -2 = -6 2 Fe must = 6+, so each is 3+. iron (III) oxide
Naming Binary Ionic Compounds Write the names of the following KCl Na3N
CrN
Sc3P2
PbO
PbO2
Na2Se
Ternary Ionic Compounds These will have polyatomic ions At least three elements name the ions NaNO3
CaSO4
CuSO3
(NH4)2O
Ternary Ionic Compounds LiCN Fe(OH)3
(NH4)2CO3
NiPO4
Writing Formulas The charges have to add up to
zero. Get charges on pieces. Cations from name on table. Anions from table or polyatomic. Balance the charges by adding
subscripts. Put polyatomics in parenthesis.
Writing Formulas Write the formula for calcium
chloride. Calcium is Ca2+ Chloride is Cl1- Ca2+ Cl1- would have a 1+ charge. Need another Cl1- Ca2+ Cl2
1- (use criss-cross method)
Write the formulas for these Lithium sulfide tin (II) oxide tin (IV) oxide Magnesium fluoride Copper (II) sulfate Iron (III) phosphide gallium nitrate Iron (III) sulfide
Write the formulas for these Ammonium chloride ammonium sulfide barium nitrate
Things to look for If cations have ( ), the number in
parenthesis is their charge. If anions end in -ide they are
probably off the periodic table (Monoatomic)
If anion ends in -ate or -ite it is polyatomic
Section 6.5Molecular Compounds and
Acids OBJECTIVES:
– Apply the rules for naming and writing formulas for binary molecular compounds.
Section 6.5Molecular Compounds and
Acids OBJECTIVES:
– Name and write formulas for common acids.
Molecular compounds made of just nonmetals smallest piece is a molecule can’t be held together because of
opposite charges. can’t use charges to figure out how
many of each atom
Molecular are easier! Ionic compounds use charges to
determine how many of each.–Have to figure out charges.–Have to figure out numbers.
Molecular compounds name tells you the number of atoms.
Uses prefixes to tell you the number
Prefixes (Table 6.5, p.159) 1 = mono- 2 = di- 3 = tri- 4 = tetra- 5 = penta- 6 = hexa- 7 = hepta- 8 = octa-
Prefixes 9 = nona- 10 = deca- To write the name, write two words:
Prefixes 9 = nona- 10 = deca- To write the name, write two words:
Prefix name Prefix name -ide
Prefixes 9 = nona- 10 = deca- To write the name, write two words:
One exception is we don’t write mono- if there is only one of the first element.
Prefix name Prefix name -ide
Prefixes 9 = nona- 10 = deca- To write the name, write two words: One exception is we don’t write mono- if
there is only one of the first element. No double vowels when writing names
(oa oo)
Prefix name Prefix name -ide
Name These N2O
NO2
Cl2O7
CBr4
CO2
BaCl2
Write formulas for these diphosphorus pentoxide tetraiodine nonoxide sulfur hexafluoride nitrogen trioxide carbon tetrahydride phosphorus trifluoride aluminum chloride
Acids
Writing names and Formulas
Acids Compounds that give off hydrogen
ions when dissolved in water. Must have H in them. will always be some H next to an
anion. The anion determines the name.
Naming acids If the anion attached to hydrogen
ends in -ide, put the prefix hydro- and change -ide to -ic acid
HCl - hydrogen ion and chloride ion hydrochloric acid H2S hydrogen ion and sulfide ion hydrosulfuric acid
Naming Acids If the anion has oxygen in it, then it
ends in -ate of -ite change the suffix -ate to -ic acid (use no
prefix) HNO3 Hydrogen and nitrate ions Nitric acid change the suffix -ite to -ous acid HNO2 Hydrogen and nitrite ions Nitrous acid
Name these HF H3P
H2SO4
H2SO3 HCN H2CrO4
Writing Acid Formulas Hydrogen will always be first name will tell you the anion make the charges cancel out. Starts with hydro?- no oxygen, -ide no hydro?, -ate comes from -ic, -ite
comes from -ous
Write formulas for these hydroiodic acid acetic acid carbonic acid phosphorous acid hydrobromic acid
Section 6.6Summary of Naming and
Formula Writing OBJECTIVES:
– Use the flowchart in Figure 6.21 to write the name of a compound when given its chemical formula.
Section 6.6Summary of Naming and
Formula Writing OBJECTIVES:
– Use the flowchart in Figure 6.23 to write a chemical formula when given the name of a compound.
Helpful to remember...1. In an ionic compound, the net ionic
charge is zero (criss-cross method)
2. An -ide ending generally indicates a binary compound
3. An -ite or -ate ending means there is a polyatomic ion that has oxygen
4. Prefixes generally mean molecular; they show the number of each atom
Helpful to remember...5. A Roman numeral after the name of
a cation shows the ionic charge of the cation
Use the handout sheets provided by your teacher!
Summary of Naming and Formula Writing
For naming, follow the flowchart- Fig. 6.21, page 161
For writing formulas, follow the flowchart from Fig. 6.23, p. 162