chapter 11 notes · atoms share electrons ... chloride ion for anions, the element name has its...
TRANSCRIPT
Bonding: the way atoms are attracted to each other to form molecules, determines nearly all of the chemical properties we see. And, as we shall see, the number “8” is very important to chemical bonding.
008: Chemical Bonds
Molecule – 2 atoms chemically combined, smallest part of compound
Compounds – atoms of 2 or more elements chemically combined, new properties not like the elements it is made of
Law of Definite Proportions
atoms combine in proportions, whole number ratios.
H2O = 2 H for every O
Atoms combine so that their outer energy level is full
Bonds – force of attraction that holds atoms together in a molecule
Octet Rule - all elements want to be happy!!!8e- in outer level, like the noble gases
When atoms combine, electrons are shared or exchanged
Atoms are electrically neutral (p+ = e-)
Ions - Atoms with a charge due to gain or loss of e-
Cation - +charge, lost e-, have more p+ than e-
Anion - –charge, gained e-, fewer p+ than e-
Polyatomic ions – group of atoms acting together and carrying a charge
Ionic Bonds: transfer e-
How can we make Na and Cl happy?
Na gives up e- to Cl
Chemical Formula = NaCl
Electropositive elements:
Readily give up electrons
to become + ions.
Electronegative elements:
Readily acquire electrons
to become - ions.
Potassium & Fluorine
K+ and F-
KF
Potassium fluoride
Aluminum oxide
Al+3O-2
Cross multiply (LCM=6)
Al2O3
+6-6=0 charge
Give up electrons Acquire electrons
He -
Ne -
Ar -
Kr -
Xe -
Rn -
F 4.0
Cl 3.0
Br 2.8
I 2.5
At 2.2
Li 1.0
Na 0.9
K 0.8
Rb 0.8
Cs 0.7
Fr 0.7
H 2.1
Be 1.5
Mg 1.2
Ca 1.0
Sr 1.0
Ba 0.9
Ra 0.9
Ti 1.5
Cr 1.6
Fe 1.8
Ni 1.8
Zn 1.8
As 2.0
CsCl
MgO
CaF2
NaCl
O 3.5
Na+ + Cl- = NaCl
Ca+2 + O-2= CaO Na+ + O-2 = Na2O
Al+3 + S-2 = Al2S
3Ca+2 + N-3 = Ca
3N
2
Ca+2 + Cl- = CaCl2
You try these!
Mg+2 + F- =
NH4
+ + PO4
-3 =
K+ + Cl- =
Al+3 + I- =
Sr+2 + P-3 =
Li+ + Br- =
Sr3P
2
AlI3
MgF2
(NH4)3PO
4
KCl
LiBr
Not NH43
PO4
METALLIC BONDS
e- are shared by all atoms
sea of electrons allow
current to flow through
metal = conductors
In sodium, 1 out of the 11 electrons is released so that
Na has two filled shells. The extra electrons move
around the metal in a “sea” of negative charge. This
negatively charged sea moves around a regular
structure of positive Na ions.
Atoms share electronsPolar Covalent – result of uneven sharing, ends have slight +/- charges
Ex. Water
Single bond: sharing 1 pair of e-
Double bond: sharing 2 pairs of e-
Triple bond: sharing 3 pairs of e-
He -
Ne -
Ar -
Kr -
Xe -
Rn -
F 4.0
Cl 3.0
Br 2.8
I 2.5
At 2.2
Li 1.0
Na 0.9
K 0.8
Rb 0.8
Cs 0.7
Fr 0.7
H 2.1
Be 1.5
Mg 1.2
Ca 1.0
Sr 1.0
Ba 0.9
Ra 0.9
Ti 1.5
Cr 1.6
Fe 1.8
Ni 1.8
Zn 1.8
As 2.0
SiC
C(diamond)
H2O
C 2.5
H2
Cl2
F2
Si 1.8
Ga 1.6
GaAs
Ge 1.8
O 2.0
co
lum
n I
VA
Sn 1.8
Pb 1.8
3.5
Lewis dot structure of a compound NH3
1) How many valence electrons does N have?
N is in group VA so it has 5 valence electrons
2) How many valence electrons does H have?
H is in group IA so each H has 1 valence electron
3) How many total valence electrons are there in this
molecule?
(3 x 1) + 5 = 8
You know it had to be 8 because it has NO CHARGE!
Non-polar: e- are shared equally btwn atoms
Bonding between atoms of the same element or atoms close to each other on table
Polar: uneven distribution of charge
unequal attraction for the shared e-
MOLECULAR ATTRACTIONS
Polar molecules are more
positively charged on one
side and more negative
on the other.
http://programs.northlandcollege.edu/biology/Biology1111/animation
s/hydrogenbonds.html
Tendency of an atom to attract a pair of e- to itself when bonded Ionic bonds: atoms differ greatly
Covalent bonds: atoms similar
Polar covalent: moderate difference
Increases from left to right & decreases from top to bottom
• Ranges from 0.7 to 4.0,
Smaller electronegativity Larger electronegativity
• Large values: tendency to acquire electrons.
Metallic
Ionic
Covalent Polar
Nonpolar
Hydrogen
http://www.chem.iastate.edu/group/Greenbowe/sect
ions/projectfolder/flashfiles/reaction/bonding1.swf
Combining ability of an atom: how many e- it will gain or lose
written as a superscript (top right)
Oxygen: O-2 gains 2 e-
The sum of oxidation numbers in a compound must be zeroH+1 & O-2 = H2O each O needs 2 H atoms
Write symbol of element w/ +oxidation#
Write symbol of element w/ -oxidation #
Add subscripts so that sum of oxidation #s is zero “cross multiply”
Use (parenthesis) around the polyatomic ions
(NH4)2
+1
Write name of cation or + polyatomic ion if it has multiple oxidation numbers, write
the charge as a Roman Numeral Fe2+ would be iron (II) ion and Fe3+ would be iron (III) ion
Write name of – polyatomic ion, if it is an anion, write the root name and
change the ending to “ide”
Naming the ions
Names of main-group monatomic ions are straightforward.
A cation takes the name of the element plus the word "ion."
Na Sr Ba
Na+
sodium ion
Sr2+
strontium ion
Ba2+
barium ion
N O Cl
N3-
nitride ion
O2-
oxide ion
Cl-
chloride ion
For anions, the element name has its
ending replaced with ide.
Example calcium chloride
– calcium is Ca2+ and chlorine is Cl-
– in order to balance charges there needs to be two negative charges to balance the 2+ on the calcium
+2 -1
Common polyatomic ion names
Formula Name
NH4+ Ammonium ion
CO32- Carbonate ion
PO43- Phosphate ion
SO42- Sulfate ion
OH- Hydroxide ion
NO3- Nitrate ion
Anions + Cations = ionic compound name
F- Fluoride ion
CO32- Carbonate ion
PO43- Phosphate ion
SO42- Sulfate ion
OH- Hydroxide ion
NO3- Nitrate ion
Cl- Chloride ion
O2- Oxide ion
S2- Sulfide ion
NH4+ Ammonium ion
Na+ Sodium ion
Ca2+ Calcium ion
Fe3+ Iron(III) ion
Ag+ Silver ion
Al3+ Aluminum ion
Ammonium fluoride
Iron phosphate
Silver oxideNote: Ag has a charge of +1 and oxide has a charge of –2 so
the chemical formula of silver oxide must be Ag2O
What is the correct name for the ionic
compound Na2SO4?
A. disodium sulfate
B. sodium sulfoxide
C. sodium sulfate
D. sodium sulfide
POLYATOMIC IONS (-1 CHARGE) H2PO4 DiHydrogen phosphate
C2H3O2 Acetate
HSO3 Hydrogen Sulfite
HCO3 Hydrogen Carbonate
NO2 Nitrite
NO3 Nitrate
CN Cyanide
OH Hydroxide
MnO4 Permanganate
ClO Hypochlorite
ClO2 Chlorite
ClO3 Chlorate
ClO4 Perchlorate
POLYATOMIC IONS (-2 CHARGE)
HPO4 Hydrogen Phosphate
C2O4 Oxalate
SO3 Sulfite
SO4 Sulfate
CO3 Carbonate
CrO4 Chromate
Cr2O7 Dichromate
SiO3 Silicate
Rule 1– If two identical elements combine then the name doesn’t change
This happens with the following elements:
1) H2
2) N2
3) O2
4) F2
5) Cl2
6) Br2
These elements always go around in pairs (diatomic molecules). For example, hydrogen looks like this
Rule 2 – When two elements join and one is a halogen, oxygen or sulphur the name ends with ____ide
e.g. Magnesium + oxygen magnesium oxide
1) Sodium + chlorine
2) Magnesium + fluorine
3) Lithium + iodine
4) Chlorine + copper
5) Oxygen + iron
6) KBr
7) LiCl
8) CaO
9) MgS
10)KF
Rule 3 – When three or more elements combine and two of them are hydrogen and oxygen the name ends with
hydroxide
e.g. Sodium + hydrogen + oxygen Sodium hydroxide
1) Potassium + hydrogen + oxygen
2) Lithium + hydrogen + oxygen
3) Calcium + hydrogen + oxygen
4) Mg(OH)2
Rule 4 – When three or more elements combine and one of them is oxygen the ending is _____ate
e.g. Copper + sulphur + oxygen Copper sulphate
1) Calcium + carbon + oxygen
2) Potassium + carbon + oxygen
3) Calcium + sulphur + oxygen
4) Magnesium + chlorine + oxygen
5) Calcium + oxygen + nitrogen
6) AgNO3
7) H2SO4
8) K2CO3
Covalent formulas Ionic formulas
H2O
CO2
NH3
H2
O2
N2
SO2
Water
Carbon dioxide
Ammonia
Hydrogen
Oxygen
Nitrogen
Sulphur dioxide
NaCl
CaCl2
MgO
HCl
H2SO4
HNO3
NaOH
Ca(OH)2
CaCO3
Al2O3
Fe2O3
Sodium chloride
Calcium chloride
Magnesium oxide
Hydrochloric acid
Sulphuric acid
Nitric acid
Sodium hydroxide
Calcium hydroxide
Calcium carbonate
Aluminium oxide
Iron oxide
Even though all atoms want the same number of electrons as the Noble Gases, some want to get or give them more than others. The magnitude of this attraction for electrons is called “Electronegativity”. The more electronegative an atom is, the more it wants the electrons.
Some atoms want to gain electrons so bad, they take them altogether to form negative ions. Some want to lose them so bad that they become positive ions.
H2O Water is a bent molecule. The lone pair of electrons
from the Lewis structure distorts its shape and it becomes a very polar molecule.
NaCl Since Na is a metal it gives up its electron to form Na+
and Cl takes the electron completely to form Cl-.
HCl The Chlorine wants the electrons more than the Hydrogen. Thus we have +δHCl-δ.
Cl2
(Cl—Cl) The Chlorine molecules want the electrons equally so they form a non-polar molecule with NO partial or full charges.
CO2
Carbon Dioxide is a linear molecule. It has no lone pairs of electrons from the Lewis structure. The two oxygen atoms pull equally and make it a non-polar molecule.
..:O:H●●
H
.. ..O::C::O●● ●●
Binary Compounds have two types of atoms
(not diatomic which has only two atoms).
Metals (Groups I, II, and III) and Non-Metals
Metal _________ + Non-Metal _________ideSodiumChlorine
Sodium Chloride NaClMetals (Transition Metals) and Non-Metals
Metal ______ +Roman Numeral (__) + Non-Metal ________ideIron IIIBromine
Iron (III) Bromide FeBr3
Compare with Iron (II) Bromide FeBr2
Metals (Transition Metals) and Non-MetalsOlder System
Metal (Latin) _______ + ous or ic + Non-Metal ________ideFerrousBromine
Ferrous Bromide FeBr2
Compare with Ferric Bromide FeBr3
Non-Metals and Non-Metals
Use Prefixes such as mono, di, tri, tetra, penta, hexa, hepta, etc.
CO2 Carbon dioxide CO Carbon monoxide
PCl3 Phosphorus trichloride CCl4 Carbon tetrachloride
N2O5 Dinitrogen pentoxide CS2 Carbon disulfide
Name the following.
CaF2
K2S
CoI2
SnF2
SnF4
OF2
CuI2
CuI
SO2
SrS
LiBr
Strontium Sulfide
Lithium Bromide
Copper (I) Iodide or Cuprous Iodide
Sulfur dioxide
Copper (II) Iodide or Cupric Iodide
Oxygen diflouride
Tin (IV) Flouride or Stannic Flouride
Tin (II) Flouride or Stannous Flouride
Cobalt (II) Iodide or Cobaltous Iodide
Potassium Sulfide
Calcium Flouride
Ammonium……………...
Nitrate……………………
Permanganate…………. .
Chlorate…………………
Hydroxide……………….
Cyanide………………….
Sulfate…………………...
Carbonate……………….
Chromate………………..
Acetate…………………..
Phosphate……………….
NH4+
NO3-
MnO4-
ClO3-
OH-
CN-
SO4 2 -
CO32-
CrO42-
C2H3O2-
PO43-