8/9/2019 Chemistry-Ch02_The Language of Chemistry
1/58
22The languageThe language
of chemistryof chemistry
8/9/2019 Chemistry-Ch02_The Language of Chemistry
2/58
2.1 Measurement2.1 Measurement
Measurements
always have a unit
always an associated uncertainty
Unit
specific standard quantity of a particular
property
used to measure all other quantities of
specific property
8/9/2019 Chemistry-Ch02_The Language of Chemistry
3/58
2.1 Measurement2.1 Measurement
The seven SI base units
Measurement Unit Symbol
length metre mmass kilogram kg
time second s
temperature kelvin K
amount of substance mole molelectric current ampere A
luminous intensity candela Cd
8/9/2019 Chemistry-Ch02_The Language of Chemistry
4/58
2.1 Measurement2.1 Measurement
The SI units for ANY physical quantity
can be built from the seven base units
For example area = length width
length and width are measured in metres
the unit of area is square metre, m2
Units undergo the same kinds of
mathematical operations as the
numbers to which they are attached
8/9/2019 Chemistry-Ch02_The Language of Chemistry
5/58
2.1 Measurement2.1 Measurement
SI or derived units are sometimes
inconvenient
Use prefixes that divide or multiply the
unit by a particular power of ten
Prefix Symbol Factor
kilo k 103
deci d 10-1
centi c 10-2
milli m 10-3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
6/58
Uncertainties and significant figures
Every measurement has an associated
uncertainty
2.1 Measurement2.1 Measurement
24.3 C
297.45 K
24.32 C
297.47 K
8/9/2019 Chemistry-Ch02_The Language of Chemistry
7/58
All figures up to and including the first
estimated figure are recorded
These figures are called significant figures
Uncertainties and significant figures
2.1 Measurement2.1 Measurement
24.3 C
297.45 K
24.32 C
297.47 K
8/9/2019 Chemistry-Ch02_The Language of Chemistry
8/58
Scientific notation expresses numbers in
terms of powers of ten
24.3 C is 2.43 101 C
24.32 C is 2.432 101 C
2.1 Measurement2.1 Measurement
Uncertainties and significant figures
24.3 C
297.45 K
24.32 C
297.47 K
8/9/2019 Chemistry-Ch02_The Language of Chemistry
9/58
2.1 Measurement2.1 Measurement
Significant figures in calculations
Multiplication or division of
measurements
Addition or subtraction of measurements
6.
..!
v
8.1 9
2.125
3.41
247.3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
10/58
Precision
Signifies how reproducible a
measurement is when made a number of
times
2.1 Measurement2.1 Measurement
8/9/2019 Chemistry-Ch02_The Language of Chemistry
11/58
2.1 Measurement2.1 Measurement
Accuracy
refers to how close the value is to the
correct value
8/9/2019 Chemistry-Ch02_The Language of Chemistry
12/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Chemical formulae
Shows the relative number of each type
of atom present in a substance
H2O
C30H34AuBClF3N O2P2PtW
A molecular formula is a chemical
formula that refers to a discrete molecule
There is a standardised way of writing
chemical formulae
8/9/2019 Chemistry-Ch02_The Language of Chemistry
13/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Binary compounds
Element further to the left of the periodic
table appears first
KCl, Al2S3
Hydrogen is the exception to this rule
LiH, NH3, H2O2, HCl
If both elements are from the samegroup the lowest element appears first
SiC, BrF3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
14/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Binary compounds
In ionic compounds the cation is written
first followed by the anion
NaBr, MgCl2
Note: a subscripted number refers ONLY
to the atom immediately preceding it.
8/9/2019 Chemistry-Ch02_The Language of Chemistry
15/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Writing chemical formulae for
compounds containing more than two
elements requires some knowledge of
the bonding within the compound.
Ionic compounds
Covalent compounds
8/9/2019 Chemistry-Ch02_The Language of Chemistry
16/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Ionic compounds
Cation followed by anion
Total charge zeroCa(NO3)2(s) Ca
2+(aq) + 2NO3-(aq)
Hydrate formation common among ionic
compoundsCa(NO3)2.4H2O
8/9/2019 Chemistry-Ch02_The Language of Chemistry
17/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Covalent compounds
Majority are carbon-based organic
compounds
Chemical formula often written carbon
first, followed by hydrogen and then the
remaining elements in alphabetical
order, e.g. C2H O, C4H9BrO
Limited structural information in the
chemical formula
8/9/2019 Chemistry-Ch02_The Language of Chemistry
18/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Structural formulae
Attempt to show the way in which the
atoms in the molecule are bonded
together
Chemical symbols still used for each
element present
Constituent atoms are placed in theorder in which they are bonded together
Bonds between neighbouring atoms are
represented as lines
8/9/2019 Chemistry-Ch02_The Language of Chemistry
19/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Structural formulae
NH3
Structural formulae do not necessarily
show the correct geometry of acompound
Presence of lone pairs of electrons is
often neglected in depictions of
molecules
NH HH
HN
H
H
NH HH
8/9/2019 Chemistry-Ch02_The Language of Chemistry
20/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Organic chemistry
Structural formulae are particularly useful
Carbon atoms bond to themselves catenation
Carbon is a tetravalent element it
prefers to form a total of 4 bonds within
a molecule These bonds may be single, double or
triple
8/9/2019 Chemistry-Ch02_The Language of Chemistry
21/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Structural formulae
C C
H
H
H
HC2H
ethane
C2H4
ethene
C2H2
ethyne
single bond double bond triple bond
C C
H
H
H
H
H
H
C C HH
C C C C C C
8/9/2019 Chemistry-Ch02_The Language of Chemistry
22/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Structural formulae can remove
ambiguities inherent in the chemical
formula
Isomers are molecules with the same
chemical formula but different structural
formula
dimethyl etherethanolC2H OC2H O
C C O H
H
H
H
H
H C O CH
H
H
H
H
H
8/9/2019 Chemistry-Ch02_The Language of Chemistry
23/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Two types of shorthand structural
formulae
condensed structural formulae
line structures
Condensed structural formulae
Constituent atoms are arranged inbonded groups, actual bonds not drawn
dimethyl ether CH3OCH3
ethanol CH3CH2OH
8/9/2019 Chemistry-Ch02_The Language of Chemistry
24/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Line structures
Are constructed according to the
following guidelines:1. All bonds except C-H bonds are shown aslines.
2. C-H bonds and H atoms attached to carbon are
not shown in the line structure.
3. Single bonds are shown as 1 line; double
bonds are shown as 2 lines; triple bonds are
shown as 3 lines.
4. Carbon atoms are not labelled. All other atoms
are labelled with their elemental symbols.
8/9/2019 Chemistry-Ch02_The Language of Chemistry
25/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Drawing line structures
C
C
C
H3C O
H
H
H
H
HH
C
H
H
H
8/9/2019 Chemistry-Ch02_The Language of Chemistry
26/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Drawing line structures
C
C
C
H3C O
H
H
H
H
HH
C
H
H
H
C
C
C
C O C
8/9/2019 Chemistry-Ch02_The Language of Chemistry
27/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Drawing line structures
C
C
C
H3C O
H
H
H
H
HH
C
H
H
H O
C
C
C
C O C
8/9/2019 Chemistry-Ch02_The Language of Chemistry
28/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Drawing line structures
C
C
C
H3C O
H
H
H
H
HH
C
H
H
H
C
C
C
C O C
CH3
CH3
H3C O CH3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
29/58
2.2 Representations of2.2 Representations of
moleculesmolecules
Drawing line structures
C
C
C
H3C O
H
H
H
H
HH
C
H
H
H
C
C
C
C O C
Me
Me
Me O Me
8/9/2019 Chemistry-Ch02_The Language of Chemistry
30/58
2.2 Representations of2.2 Representations of
moleculesmolecules
H
H
H
H
CH3 CH3
HH H
H
Three-dimensional structures
To draw a three-dimensional structure
add perspective to a structural formula or
line structure
cis isomer trans isomer
H
H
H
H
H CH3
HCH3 H
H
8/9/2019 Chemistry-Ch02_The Language of Chemistry
31/58
2.2 Representations of2.2 Representations of
moleculesmolecules
X
XX
X
Three-dimensional structural formulae
ML
L L
L
L
L
Tetrahedral
Conventional wayto draw 4 bonds
around a single
carbon atom
Octahedral
Transition metal ioncomplex
ML
8/9/2019 Chemistry-Ch02_The Language of Chemistry
32/58
2.2 Representations of2.2 Representations of
moleculesmolecules
X
XX
X
Three-dimensional structural formulae
Tetrahedral
Conventional wayto draw 4 bonds
around a single
carbon atom
Octahedral
Transition metal ioncomplex
ML
L
L
L
L
L
L
8/9/2019 Chemistry-Ch02_The Language of Chemistry
33/58
2.2 Representations of2.2 Representations ofmoleculesmolecules
Three-dimensional structures
8/9/2019 Chemistry-Ch02_The Language of Chemistry
34/58
2.3 Nomenclature2.3 Nomenclature
Nomenclature the system for
naming of compounds
International Union of Pure and AppliedChemistry (IUPAC)
Some compounds are better known by
their common unsystematic name
rather than their systematic IUPAC
name
The systematic name of water is oxidane
8/9/2019 Chemistry-Ch02_The Language of Chemistry
35/58
1. The element closer to the left of theperiodic table appears first.
If both elements are from the same
group of the periodic table, the lower
one appears first.
Nitrogen monoxide Nitrogen dioxide Dinitrogen pentoxide
2.3 Nomenclature2.3 Nomenclature
Naming Inorganic compounds
Nonmetallic binary compounds
Guidelines for naming:
NO NO2 N2O5Nitrogen monoxide Nitrogen dioxide Dinitrogen pentoxide
8/9/2019 Chemistry-Ch02_The Language of Chemistry
36/58
2. The element that appears first retainsits elemental name.
Nitrogen monoxide Nitrogen dioxide Dinitrogen pentoxide
2.3 Nomenclature2.3 Nomenclature
Naming Inorganic compounds
Nonmetallic binary compounds
Guidelines for naming:
NO NO2 N2O5Nitrogen monoxide Nitrogen dioxide Dinitrogen pentoxide
8/9/2019 Chemistry-Ch02_The Language of Chemistry
37/58
3. The second element begins with aroot derived from its elemental name
and ends with the suffix ide.
2.3 Nomenclature2.3 Nomenclature
Naming Inorganic compounds
Nonmetallic binary compounds
Guidelines for naming:
NO NO2 N2O5Nitrogen monoxide Nitrogen dioxide Dinitrogen pentoxide
8/9/2019 Chemistry-Ch02_The Language of Chemistry
38/58
4. When there is more than one atom ofa given element in the formula, the
name of the element usually contains
a prefix that specifies the number of
atoms present.
Nitrogen monoxide Nitrogen dioxide Dinitrogen pentoxide
2.3 Nomenclature2.3 Nomenclature
Naming Inorganic compounds
Nonmetallic binary compounds
Guidelines for naming:
NO NO2 N2O5Nitrogen monoxide Nitrogen dioxide Dinitrogen pentoxide
8/9/2019 Chemistry-Ch02_The Language of Chemistry
39/58
2.3 Nomenclature2.3 Nomenclature
Binary compounds of hydrogen
Hydrogen requires special consideration
It may appear first or second in the
chemical formula of a compound,
therefore first or second in the name
Lithium hydride LiH
Hydrogen fluoride HF Hydrogen sulfide H2S
Calcium hydride CaH2
8/9/2019 Chemistry-Ch02_The Language of Chemistry
40/58
2.3 Nomenclature2.3 Nomenclature
Ionic compounds
Binary ionic compounds are written with
the cation first and the anion, which
takes the suffix ide, last
Potassium iodide KI
Calcium fluoride CaF2
Ionic compounds may containpolyatomic ions
Ammonium NH4+
Nitrate NO3-
8/9/2019 Chemistry-Ch02_The Language of Chemistry
41/58
1. The name has a root taken from the
name of the central atom
Carbonate CO32-
Nitrite NO2-
2.3 Nomenclature2.3 Nomenclature
Ionic compounds
Anions containing a central atom
surrounded by oxygen atoms are known
as oxoanions. Naming rules:
8/9/2019 Chemistry-Ch02_The Language of Chemistry
42/58
2. When an element forms 2 different
oxoanions, the one with fewer oxygen
atoms ends in ite, and the otherends in ate
Sulfite SO32-
Sulfate SO42-
2.3 Nomenclature2.3 Nomenclature
Ionic compounds
Anions containing a central atom
surrounded by oxygen atoms are known
as oxoanions. Naming rules:
8/9/2019 Chemistry-Ch02_The Language of Chemistry
43/58
3. Chlorine, bromine and iodine each
form 4 different oxoanions that are
distinguished by prefixes and suffixes Hypobromite BrO-
Bromite BrO2-
Bromate BrO3-
2.3 Nomenclature2.3 Nomenclature
Ionic compounds
Anions containing a central atom
surrounded by oxygen atoms are known
as oxoanions. Naming rules:
8/9/2019 Chemistry-Ch02_The Language of Chemistry
44/58
4. A polyatomic anion with a charge
more negative than 1- may add H+ to
give another anion. These anions arenamed from the parent anion by
adding the word hydrogen
Hydrogen carbonate HCO3-
Hydrogen phosphate H2PO4-
2.3 Nomenclature2.3 Nomenclature
Ionic compounds
Anions containing a central atom
surrounded by oxygen atoms are known
as oxoanions. Naming rules:
8/9/2019 Chemistry-Ch02_The Language of Chemistry
45/58
2.3 Nomenclature2.3 Nomenclature
Organic compounds
Composed primarily of carbon and
hydrogen atoms
Naming system based on the number of
carbon atoms in a particular molecule
Functional groups
A group of one or more atoms within amolecule bonded in a particular fashion
Usually the point of reaction within a
molecule
8/9/2019 Chemistry-Ch02_The Language of Chemistry
46/58
Organic compounds
Named according to their functional
groups
Functional Name of Found
group group inhydroxyl alcohols
carbonyl aldehydes
carbonyl ketones
carboxyl carboxylic acids
2.3 Nomenclature2.3 Nomenclature
R OH
C
O
R R
C
O
R OH
C
O
R H
8/9/2019 Chemistry-Ch02_The Language of Chemistry
47/58
2.3 Nomenclature2.3 Nomenclature
Alkanes
Molecules that contain only carbon and
hydrogen
Carbon atoms are joined by single bond
only
2 parts to the name of an alkane
Prefix: indicating the number of carbonatoms in the longest chain
Ending: -ane
8/9/2019 Chemistry-Ch02_The Language of Chemistry
48/58
2.3 Nomenclature2.3 Nomenclature
IUPAC rules for naming alkanes:
1. The name of an alkane with an
unbranched chain of carbon atoms
consists of a prefix showing the number ofcarbon atoms in the chain and the ending
-ane
CH3CH2CH2CH3
butane
8/9/2019 Chemistry-Ch02_The Language of Chemistry
49/58
2.3 Nomenclature2.3 Nomenclature
IUPAC rules for naming alkanes:
2. For the branched-chain alkanes, the
longest chain of carbon atoms is the
parent chain, and its name becomes theroot name
12345
2-methylpentane
CH3CH2CH2CHCH3CH3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
50/58
2.3 Nomenclature2.3 Nomenclature
IUPAC rules for naming alkanes:
3. For an alkane with 1 substituent, number
the parent chain so that the carbon atom
bearing the substituent is given the lowestpossible number
2-methylpentane
12345CH3CH2CH2CHCH3
CH3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
51/58
2.3 Nomenclature2.3 Nomenclature
IUPAC rules for naming alkanes:
4. Give the substituent on the parent chain a
name and number. The number shows
the carbon atom of the parent chain towhich the substituent is bonded. Use a
hyphen to connect the number to the
name
1 2 3CH3CHCH3
CH3
2-methylpropane
8/9/2019 Chemistry-Ch02_The Language of Chemistry
52/58
2.3 Nomenclature2.3 Nomenclature
IUPAC rules for naming alkanes:
5. If there are two or more identical
substituents, number the parent chain
from the end that gives the lower numberto the substituent closest to the end of the
chain
12345
2,4-dimethylhexane
CH3CH2CHCH2CH2CH3
CH3 CH3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
53/58
CH3CH2CHCH2CHCH2CH3
CH2CH3
CH31 2 3 4 5 7
3-ethyl-5-methylheptane
2.3 Nomenclature2.3 Nomenclature
IUPAC rules for naming alkanes:
. If there are two or more different
substituents, list them in alphabetical
order, and number the chain from the endthat gives the lower number to the
substituent encountered first
8/9/2019 Chemistry-Ch02_The Language of Chemistry
54/58
1 2 3 4 5
4-ethyl-2,2-dimethylhexane
2.3 Nomenclature2.3 Nomenclature
IUPAC rules for naming alkanes:
7. The prefixes di, tri, tetra etc. and the
hyphenated prefixes sec- and tert- are
disregarded for the purposes of placingthe substituents in alphabetical order
CH3CCH2CHCH2CH3CH3
CH3
CH2CH3
8/9/2019 Chemistry-Ch02_The Language of Chemistry
55/58
2.3 Nomenclature2.3 Nomenclature
Constitutional isomerism in alkanes
Compounds with the same chemical
formula but a different order of
attachment of the constituent atoms
Usually distinguishable by their differing
physical properties
pentane
2,2-dimethylpropane
2-methylbutane
8/9/2019 Chemistry-Ch02_The Language of Chemistry
56/58
2.3 Nomenclature2.3 Nomenclature
General organic nomenclature The name of any compound with a chain of
carbon atoms consists of 3 parts.
1. A prefix: shows the number of carbonatoms in the parent chain
2. An infix: shows the nature of the carbon-
carbon bonds in the parent chain
3. Asuffix: shows the class of compound towhich the substance belongs, and
therefore the functional group(s) present
in the compound
8/9/2019 Chemistry-Ch02_The Language of Chemistry
57/58
2.3 Nomenclature2.3 Nomenclature
General organic nomenclature
H3CHC CH2 CH3CH2CH2CH2COH
O
propene
a carbon-carbon
double bond
a
hydrocarbon
3 carbon
atoms
pentanoic acid
only carbon-carbon
single bonds
a COOH
(carboxyl)
group
5 carbon
atoms
8/9/2019 Chemistry-Ch02_The Language of Chemistry
58/58