Atoms Elements Molecules Ions and Compounds Early in the 19 th century John Dalton developed atomic theory His theory explained the best available experimental data at that time His theory has been modified since then with the discovery of other data but his work was the initial ground ID: 491490
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Slide1
1
Topic 2Atoms, Elements, Molecules, Ions, and Compounds
Early in the 19
th
century John Dalton developed atomic theory. His theory explained the best available experimental data at that time. His theory has been modified since then with the discovery of other data, but his work was the initial ground work that we will examine first.Slide2
Atomic Theory of Matter
Postulates of Dalton’s Atomic Theory1.)All matter is composed of indivisible atoms. An atom is an extremely small particle of matter that retains its identity during chemical reactions. 2.)An element is a type of matter composed of only one kind of atom, each atom of a given element having the same properties. Mass is one such property. Thus the atoms of a given element have a characteristic mass. 2
Protons, neutrons, electrons
Atoms have different isotopes that have the same # protons but different # neutrons and hence different mass. Note: #protons gives identity of atom.
Later found indivisible to be untrue.
Later found all atoms of the same element does not have to have the same mass.Slide3
Atomic Theory of Matter
Postulates of Dalton’s Atomic Theory33.) A compound is a type of matter composed of atoms of two or more elements chemically combined in fixed proportions. The relative numbers of any two kinds of atoms in a compound occur in simple ratios.
Water, for example, consists of hydrogen and oxygen in a 2 to 1 ratio (2H: 1O
) for all molecules of water.Slide4
Atomic Theory of Matter
Postulates of Dalton’s Atomic Theory44.) A chemical reaction consists of the rearrangements of the atoms present in the reacting substances to give new chemical combinations present in the substances formed by the reaction (new chemical with different properties).
5.) Atoms are not created, destroyed, or broken into smaller particles by any chemical reaction.
Na
(s)
+ Cl
2
(g)
2
2 NaCl
(s)
Protons, neutrons, electrons
i.e., solid sodium mixed with chlorine gas forms a new substance, salt, with totally different properties from the starting materials.
Once again, later found indivisible to be untrue.Slide5
Atomic Theory of Matter
The Structure of the Atom5Although Dalton postulated that atoms were indivisible, experiments at the beginning of the 1900’s showed that atoms themselves consist of particles.
Experiments by Ernest Rutherford in 1910 showed that the atom was mostly “empty space.”Slide6
Atomic Theory of Matter
6These experiments showed that the atom consists of two kinds of particles: a nucleus, the atom’s central core, which is positively charged and contains most of the atom’s mass, and one or more electrons.
Electrons
are very light, negatively charged particles that exist in the region around the atom’s positively charged nucleus.
Nucleus
(
+
)
e
-Slide7
Atomic Theory of Matter
7In 1897, the British physicist J. J. Thompson conducted a series of experiments that showed that atoms were not indivisible particles but instead made of smaller particles.From his experiments, Thompson calculated the ratio of the electron’s mass,
m
e
, to its electric charge,
e
. Slide8
Atomic Theory of Matter
8In 1909, U.S. physicist, Robert Millikan obtained the charge on the electron (1.602 x 10-19 C).
These two
discoveries (Millikan and Thompson)
combined provided us with the electron’s mass of
9.109 x 10
-31
kg, which is more than 1800 times smaller than the mass of the lightest atom (hydrogen) thereby proving that the atom is made up of smaller particles.
These experiments showed that the electron was indeed a subatomic particle.Slide9
Atomic Theory of Matter
The nuclear model of the atom.9Ernest Rutherford, a British physicist, put forth the idea of the nuclear model of the atom in 1911, based on experiments done in his laboratory by Hans Geiger and Ernest Morrison. Rutherford’s famous gold leaf experiment gave credibility to the theory that the majority of the mass of the atom was concentrated in a very small nucleus. Positively charged alpha particles were directed at a metal foil. Only 1/8000 were deflected indicating that the nucleus was extremely small and positively charged. Only those alpha particles that directly hit the nucleus were deflected; the rest passed through.Slide10
Atomic Theory of Matter
10Most of the mass of an atom is in the nucleus; however, the nucleus occupies only a very small portion of the space in the atom.The diameter of an atom is approximately 100 pm while the diameter of the nucleus is approximately 0.001 pm. For comparison, if an atom was 3 miles in diameter, the nucleus would be the size of a golf ball.The nucleus of an atom is composed of two different kinds of particles: protons (+) and neutrons (neutral).
An important property of the nucleus is its
positive electric charge
.Slide11
Atomic Theory of Matter
11A proton is the nuclear particle having a positive charge equal to that of the electron’s (a “unit” charge) and a mass more than 1800 times that of the electron. It is for this reason that we refer to H as a pure proton.The number of protons in the nucleus of an atom is referred to as its
atomic number
(
Z
)
and
gives the identity of an element. All species that have same #p have the same properties.
neutral species: #p = #e
-
#p remains constant in species;
#e
-
can vary and dictates the charge of species
H Z=1 1p, 1e
-
Na Z=11 11p, 11e
-
Cl Z=17 17p, 17e
-
Cl
-
Z=17 17p,
18e
-
Na
+
Z=11 11p,
10e
-
+ charge, more p than e
-
-
charge,
more e
-
than pSlide12
Atomic Theory of Matter
12An element is a substance whose atoms all have the same atomic number (Z). The #protons
defines the identity of an atom and can be found on the periodic table (
large number in top of element box
).
The
neutron
is a nuclear particle having a mass almost identical to that of a proton, but
no electric charge. The charge of the nucleus comes from the #protons. The atoms may have different masses because of different #neutrons (
isotopes).
Summary of masses and charges of the three fundamental particles:particlemass, kgcharge, Crelative chargelocationelectron, e-9.109 x 10-31
-1.602 x 10-19-1
outside nucleusproton, p
1.6726 x 10
-27
1.602 x 10
-19
+1
nucleus
neutron, n
1.6749 x 10
-27
0
0
nucleusSlide13
13
The mass number (A) is the total number of protons and neutrons in a nucleus.
A
nuclide
is an atom characterized by a definite atomic number and mass number.
The shorthand notation for a nuclide consists of its symbol with the atomic number, Z, as a subscript on the left and its mass number, A, as a superscript on the left.
A
=
#p
+ #n =
Z + #n
How many neutrons does sodium 23 have?
A = 23
,
Z = 11
(number on periodic
table)
A
=
Z
+ #n
23
=
11
+ #n
#n =
23
-
11
= 12
11p, 12 n,
11e
-
+
11p, 12 n,
10e
-Slide14
What is the nuclide symbol for a nucleus that consists of
17 protons, 18 neutrons, and 17 electrons?How many protons, neutrons, and electrons are in the following nucleus
14
HW
9
HW
10
What’s the element?
17 p
atomic number on periodic table for chorine
A = #p + #n = 17 + 18 = 35
35 p
45 n
A = #p + #n
80 = 35 + #n
#n = 80 – 35 = 45 n
36 e
-
Note: #e
-
= #p; therefore, neutral species
Note: #e
-
> #p;
therefore, negatively charged species
35e
-
+ one additional
e
-
based on -1 charge = 36 e
-
code for both:
protonSlide15
Atomic Theory of Matter
15The fractional abundance is the fraction of a sample of atoms that is composed of a particular isotope. Isotopes
are atoms whose nuclei have the same atomic number (Z) but different mass numbers (A); that is, the nuclei have the same number of protons but different numbers of
neutrons thereby causing them to have different masses.
Chlorine, for example, exists as two isotopes: chlorine-35 and chlorine-37.
17p,
18 n
, 17e
-
17p,
20 n
, 17e
-
(0.75771)(34.97 amu) + (0.24229) (36.97 amu) = 35.45 amu
Frac abund = 75.771%
Mass = 34.97 amu
Frac abund = 24.229%
Mass = 36.97 amu
Note: The mixture of isotope masses make up the actual mass of the element given on periodic table.
Cl
has a mass of 35.45
amu
which is based on the two isotopes of Cl-35 and Cl-37.Slide16
Atomic Weights
Calculate the atomic weight of boron, B, from the following data: ISOTOPE ISOTOPIC MASS (amu) FRACTIONAL ABUNDANCE B-10 10.013 0.1978 (19.78%) B-11 11.009 0.8022 (80.22%)16
B-10: 10.013
amu
x 0.1978 =
1.98
0
B-11: 11.009
amu
x 0.8022 = 8.831 10.811 = 10.811 amu ( = atomic wt.)
HW
11
Note: fractional abundances must add to 1 (100%)
Note: mass on periodic table matches 10.811
amu
(weighted average of isotopes)
code:
amuSlide17
Atomic Weights
Dalton’s Relative Atomic Masses17Since Dalton could not weigh individual atoms, he devised experiments to measure their masses relative to the hydrogen atom.Hydrogen was chosen as it was believed to be the lightest element. Daltons assigned hydrogen a mass of
1 (1 Dalton = mass of H).
For example, he found that carbon weighed 12 times more than hydrogen. He therefore assigned carbon a mass of
12 ( mass of carbon = 12 Daltons).Slide18
Atomic Weights
Dalton’s Relative Atomic Masses18Dalton’s atomic weight scale was eventually replaced in 1961, by the present carbon–12 mass scale.One atomic mass unit (amu
)
is, therefore, a mass unit equal to exactly
1/12 the mass of a carbon–12 atom
.
On this modern scale, the atomic weight of an element is the average atomic mass for the naturally occurring element, expressed in atomic mass units. Periodic table is based on atom mass with units of amu
.
Na - 23.1
amu mass of 1 atom of sodiumSlide19
The Periodic Table
In 1869, Dmitri Mendeleev discovered that if the known elements were arranged in order of atomic mass (A), they could be placed in horizontal rows such that the elements in the vertical columns had similar properties.19periodic table - tabular arrangement of elements in rows and columns, highlighting the regular repetition of properties of the elements. periodic law – states that certain sets of physical and chemical properties recur at regular intervals (periodically) when the elements are arranged according to increasing
atomic number (Z
).
Note: eventually changed from atomic mass to atomic number because of a couple of anomalies.Slide20
Figure: A modern form of the periodic table.
20
anomaliesSlide21
The Periodic Table
Periods and Groups21A period consists of the elements in any one horizontal row of the periodic table.
A
group
consists of the elements in any one column of the periodic
table (similar properties/structure).
The groups are usually
numbered (North American uses roman numbers and A/B; IUPAC 1-18).The eight “A
” groups are called main group (or representative) elements. Slide22
The Periodic Table
Periods and Groups22The “B” groups are called transition elements.
The two rows of elements at the bottom of the table are called
inner transition elements
.
Elements in any one group have similar
properties because their outer shells have the same number of valence electron (discuss in later sections). Slide23
The Periodic Table
Periods and Groups23The elements in group IA (except H) - alkali metals
The group VIIA elements -
halogens
The elements in group IIA -
alkaline earth metals,
The group VIIIA elements –
noble gases (monoatomic)
Diatomic elements –
H
2, N2
, O2, F2
, Cl
2
, Br
2
, I
2
Most
species
are solids at room temperature; H
2
, N
2
, O
2
, F
2, Cl2, and noble gases are gases; Br2 and Hg are liquids.Slide24
24
HW 12
metals
nonmetals
Metallic character
Metallic character
Metals, Nonmetals, and Metalloids
– generally, left of
staircase
are metals
,
touching staircase are metalloids
, right of staircase
are nonmetals
. This is important for determining bond type, using proper terminology, and making decisions.
code:
tableSlide25
Chemical Formulas; Molecular and Ionic Substances
The chemical formula of a substance is a notation using atomic symbols with subscripts to convey the relative proportions of atoms of the different elements in a substance.25aluminum oxide, Al2O3 2Al:3O ratio
sodium chloride,
NaCl
1Na:1Cl
ratio
calcium nitrate, Ca(NO3
)2 1Ca:2NO
3- ratio or 1Ca:2N:6O ratioSlide26
26
A
molecule
is a definite group of atoms that are chemically bonded together through sharing of electrons (covalent bonding, generally nonmetal-nonmetal including H).
Chemical Formulas;
Molecular
and
Ionic Substances
Molecular substances
A
molecular substance is a substance that is composed of molecules, all of which are alike.A molecular formula gives the exact number of atoms of elements in a molecule (i.e. C2H6O).Structural formulas show how the atoms are bonded to one another in a molecule. i.e.
ethanol (C2H
6O) has a structural formula of CH
3
CH
2
OH
involves
covalent bond
– share electrons between atoms – typically nonmetal/nonmetal
involves
ionic bond
– transfer electrons between atoms – attraction between charged particles – typically metal/nonmetal or polyatomic ions
C : C
Na
+
Cl
-Slide27
27
Although many substances are molecular, others are composed of
ions
(
charged
particles)
that
have
transferred electrons and have ionic bonding; occurs generally with metal-nonmetal interactions.
Ionic substances
An ion is an electrically charged particle obtained from an atom or chemically bonded group of atoms by adding or removing electrons.Sodium chloride is a substance made up of ions.
Na
Cl
+
1e
-
-
Na
+
Cl
-Slide28
28
The
formula
of an ionic compound is written by giving the smallest possible whole-number ratio of different ions in the substance.
Chemical Formulas; Molecular and Ionic Substances
Ionic substances
The
formula unit
of the substance is the group of atoms or ions explicitly symbolized by its formula.
Covalent bond (share e
-)Ionic bond (transfer e-/ attraction charged particlesnm –nm m – nm and charged ionsMoleculesFormula unitMolecular substanceIonic substance
Molecular formulaformula
C :
O
Na
+
Cl
-Slide29
29
When an atom gains extra electrons, it becomes a negatively charged ion, called an
anion (more electrons than protons
)
.
i.e
,
Cl-
Ionic substances
An atom that loses electrons becomes a positively charged ion, called a
cation (more protons than electrons). i.e., Na+An ionic compound is a compound composed of cations and anions.
NaCl
CaBr
2
Na
2
SO
4
CO
2
Answer the following questions for species below:
ionic
or
molecular substance;
formula unit or molecule; ionic or covalent bonds involved?
ionic substance; formula unit; ionic bond
ionic substance; formula unit; ionic bonds
ionic substance; formula unit; ionic and covalent
bonds in SO
4
2-
molecular substance; molecule; covalent bondsSlide30
30
Ions in Aqueous Solution
Many (not all) ionic compounds (ionic bond/m-nm) dissociate into independent ions when dissolved in water
NaCl
(s)
Na
+(aq) + Cl-(aq
) Soluble ionic compounds
dissociate 100% - referred to as strong electrolytes – breaks into charged particles until reaches saturation point.
Soluble salt
charges particlesSlide31
31
Ions in Aqueous Solution
Most molecular (covalent bond/nm-nm) compounds dissolve but do not dissociate into ions, exception acids.
C
6
H
12
O6 (s) C6H12O6 (aq)
These compounds are referred to as nonelectrolytes; no charged particles; soluble to saturation point but no ions formed.
How would
sodium sulfate dissolve based on bonding?
Na2SO
4
(s)
2Na
+
(
aq
) +
SO
4
2-
(
aq
)
no charges particles; remains whole
ionic bond dissociates while covalent bonds in sulfate remain intactSlide32
32
Most ionic compounds
contain
metal
and nonmetal
atoms (as well as polyatomic ions)
;
for example, NaCl.
Chemical Substances; Formulas and Names
Ionic compounds
You name an ionic compound by giving the name of the cation followed by the name of the anion with -ide.Sodium chloride, NaCl Calcium Iodide
, CaI2Potassium Brom
ide, KBr
We give the monatomic ion name for the
cations
and anions when naming compounds. A
monatomic ion
is an ion formed from a single atom.Slide33
33
Most of the main group metals form cations with the charge
equal
to their
roman group
number
.
How do we get the charge for ions?
Rules for predicting charges on monatomic ions
The charge on a monatomic anion for a nonmetal equals the
roman group number minus 8.Most transition elements form more than one ion, each with a different charge (exceptions Cd2+, Zn2+, Ag+). Other important elements with variable chargePb4+, Pb2+
Sn4+, Sn
2+ As5+, As
3+
Sb
5+
, Sb
3+
1+
2+
3+
4+
0
1-
2-
3-
4-
variesSlide34
34
Monatomic cations are named after the element. For example, Al
3+
is called the aluminum ion.
Rules for naming monatomic ions
If there is
more than one
cation
of an element (
charge
), a Roman numeral in parentheses denoting the charge on the ion is used. This often occurs with transition elements.Na+ sodium ion Ca2+ calcium ionFe2+ iron (II) ion Fe3+ iron (III) ion
Older name: higher ox state (charge) –
ic, / lower, -
ous
Fe
3+
ferr
ic
ion Fe
2+
ferr
ous
ion Cu
2+
cupric ionCu
+ cupr
ous ion Hg2+ mercuric ion Hg22+ mercurous ionalso done with Pb4+, Pb2+
; Sn4+
, Sn2+
;
As
5+
,
As
3+
;
Sb
5+
,
Sb
3
+
.
For the
names of the
mona
tomic
anions
,
use the stem name of the element followed by the suffix
–
ide
. For
example brom
ine
, the anion is called brom
ide
ion,
Br
-
. Slide35
35
The formula of an ionic compound is written by giving the smallest possible whole-number ratio of different ions in the substance.
Sodium chloride
Na
+
Cl
- Iron (III) sulfate Fe3+
SO42-
Chromium (III) oxide
Cr3+ O2-Calcium nitrate Ca2+ NO3-Sodium phosphate Na+ PO43-
Strontium oxide Sr
2+ O2-
NaCl
SrO
Na
3
PO
4
Ca(NO
3
)
2
Cr
2
O
3
Fe
2
(SO
4
)
3
Based on the charge of the ions and balancing the overall charge on the compound by adjusting the number of ions, a formula is written. Note the sum of all the charges must equal zero, and you do not display the charges in the final formula.
ions and charges
formula
2
Fe
3+
=
6+
charge
3
SO
4
2-
=
6-
charge
balanced
1
Na
+
=
1+
charge
1
Cl
-
=
1-
charge
balanced
Generally, you can crisscross the charge of one ion
as
the subscript on the second
ion,
reducing when possible.
Roman number tells charge of transition metal
2
3
HW
13 & 14
code for both:
formulaSlide36
36
Naming Ionic Binary Compounds
NaF
-
- lithium chloride
MgO
-
MnBr2 -- cobalt (III) oxide
- copper (II) chloride or cupric chloride
sodium fl
uoride
LiCl
magnesium oxide
manganese (
II
) bromide
Co
2
O
3
CuCl
2
To name a compound, you must know if it is a molecular or ionic compound so that you know which rules to follow. If you have a metal-nonmetal (or polyatomic ion), it is an ionic compound where you name the metal first then the nonmetal with changing the ending to –ide. If it is a transition metal, you must include the charge of the metal (Roman numbers).
If you have nonmetal-nonmetal, it is a molecular compound which we haven’t discussed yet.
The charge on
Mn
must be 2+ to balance out the 2Br
-
charges.
The Roman number 3 tells us the charge on Co is 3+ which helps us determine the formula knowing that O is 2-.Slide37
37
A
polyatomic ion
is an ion consisting of two or more atoms chemically bonded together and carrying a net electric charge
. We name the compounds the same way we just discussed except each polyatomic ion has a particular name.
Books typically have a table that lists common
polyatomic ions. Most are
oxo anions – consists of oxygen with another element (central element).
Chemical Substances; Formulas and Names
Polyatomic ions
NO3- nitrate
SO42- sulf
ate
NO
2
-
nitr
ite
SO
3
2-
sulf
ite
Most
groups have
–ate, -ite endings and differ by #O.Mn, Br, Cl,
I have per- -ate, -ate
, -ite, hypo- -ite.Slide38
38
Ions You Should Know
Polyatomic ions
NH
4
+
- Ammonium
OH- - HydroxideCN- - CyanideSO42- - Sulfate
SO32- - Sulfite
ClO4- - perchlorate
ClO3- - chlorateClO2- - chloriteClO- - hypochloriteHg22+ - mercury (I) or mecurous S2O32- - thiosulfateSCN- - thiocyanate
CNO- - cyanateMnO
4- - permanganate
O
2
2-
- Peroxide
PO
4
3-
- Phosphate
PO
3
3-
-
Phosphite
CO32- - CarbonateHCO3- - Bicarbonate or Hydrogen CarbonateN3- - azideNO3-
- nitrateNO2- - nitriteC
2H3O2- or CH3COO- - acetateCr2O72- - dichromateCrO42- - chromateC2O42- - oxalateHSO4- - bisulfate or hydrogen sulfate
H2PO4- - dihydrogen
phosphate Slide39
39
SnSO
4
sodium sulfite
Ca
(
ClO)2 barium hydroxide potassium perchlorateCr2(SO4)
3 magnesium nitride
Fe3(PO4)2
titanium (IV) nitrate
tin (II) sulfate or stannous sulfate
Na
2
SO
3
calcium hypochlorite
Ba(OH)
2
KClO
4
chromium (III) sulfate
Mg
3
N
2
iron (II) phosphate or ferrous phosphate
Ti(NO
3
)
4
Note: Not a polyatomic ion; monoatomic anion of N.Slide40
40
Molecular compounds
Binary compounds composed of two nonmetals are usually
molecular
and are named using a
prefix system (name same as ionic except must indicate how many atoms are present using mono, di, tri, etc.)
.
No charges
(share electrons) involved with molecular compounds, but we typically put more metallic compound first
.Which way is the correct way to write the following formula based on putting the more metallic compound first?
Chemical Substances; Formulas and Names
NF3
F3NSlide41
41
The name of the compound has the elements in the order given in the formula.
Binary molecular compounds
You name the first element using the exact element name.
Name the second element by writing the stem name of the element with the suffix “–
ide
.”
If there is more than one atom of any given element, you add a prefix (
di
, tri, tetra,
penta, hexa, hepta, octa, etc.) Chemical Substances; Formulas and NamesSlide42
42
Binary molecular compounds
N
2
O
3
SF
4
chlorine dioxide
sulfur hexafluorideCl2O7HCl (g) Name this compound but think about bonding:MgCl2
Older names: water - H2O, ammonia – NH
3, hydrogen sulfide – H
2
S, nitric oxide – NO, hydrazine – N
2
H
4
di
nitrogen
tri
oxide
sulfur
tetra
fluoride
ClO
2
SF
6
di
chlorine
hept
oxide
hydrogen chloride
magnesium chloride; ionic
comp,
no prefix
To name a compound, you must know if it is a molecular or ionic compound so that you know which rules to follow. If you have a metal-nonmetal (or polyatomic ion), it is an ionic compound where you name the metal first then the nonmetal with changing the ending to –ide. If you have nonmetal-nonmetal, it is a molecular compound which you do similarly as the ionic compound except that you must use prefixes to indicate the number of atoms.
Drop the “a” on prefix if you encounter double vowel in name.
Since this is a gas, we name using molecular rules; however, if acid we have other rules
.Slide43
43
Acids
are traditionally defined as compounds with a potential H
+
as the cation.
Acids
Binary
acids
consist of a hydrogen ion and any single
anion in aqueous solution.
For example, HCl (aq) is hydrochloric acid. Binary acid: hydrostemic acidAn oxoacid is an acid containing hydrogen, oxygen, and another element. An example is HNO3
, nitric acid. The
oxoacids are a derivation of the oxoanions
we discussed earlier.
Chemical Substances; Formulas and NamesSlide44
44
oxoacids
Anion prefix/suffix
acid prefix/
suffic
per- -ate ion per- -ic acid -ate ion -ic acid -
ite ion -ous acid
hypo- -ite ion hypo- -ous acid
NO3- nitrate ion HNO3 nitric acidNO2- nitrite ion HNO2 nitrous acidClO4- perchlorate ion HClO4 perchloric acid
SO
4
2-
sulf
ate
ion H
2
SO
4
sulf
uric
acid
PO
4
3-
phosph
ate
ion H3PO4 phosphoric acidIf you learn the
oxoanions, you can easily adapt to naming the oxoacids:
-ate -ic and –
ite
-
ous
For some species there is a change in spelling in the name.Slide45
Chemical Substances; Formulas and Names
Hydrates45A hydrate is a compound that contains water molecules weakly bound in its crystals.
Hydrates are named from the anhydrous (dry) compound, followed by the word “hydrate” with a prefix to indicate the number of water molecules per formula unit of the compound.
CuSO
4
.
5
H2O Magnesium sulfate hepta
hydrate
HW 15 - 18
copper(II)sulfate
penta
hydrate
MgSO
4
.
7
H
2
O
code for all:
namesSlide46
Chemical Substances; Formulas and Names
Naming simple compounds46Chemical compounds are classified as organic or inorganic.
Organic compounds
are compounds that contain carbon combined with other elements, such as hydrogen, oxygen, and nitrogen.
Inorganic compounds
are compounds composed of elements other than carbon.Slide47
Chemical Formulas; Molecular and Ionic Substances
Organic compounds47An important class of molecular substances that contain carbon is the organic compounds.
Organic compounds make up the majority of all known compounds.
The simplest organic compounds are
hydrocarbons
- compounds containing
only hydrogen and carbon
.Common examples include methane, CH4, ethane, C2H
6, and propane, C3H
8.Slide48
Classifying CompoundsOrganic vs. Inorganic
in the 18th century, compounds from living things were called organic; compounds from the nonliving environment were called inorganicorganic compounds easily decomposed and could not be made in 18th century labinorganic compounds very difficult to decompose, but able to be synthesized48Slide49
Modern Classifying Compounds
Organic vs. Inorganictoday we commonly make organic compounds in the lab and find them all around usorganic compounds are mainly made of C and H, sometimes with O, N, P, S, and trace amounts of other elementsthe main element that is the focus of organic chemistry is carbon 49Slide50
Carbon Bonding
carbon atoms bond almost exclusively covalentlycompounds with ionic bonding C are generally inorganicwhen C bonds, it forms 4 covalent bonds4 single, 1 double + 2 singles, 2 double, or 1 triple + 1 singlecarbon is unique in that it can form limitless chains of C atoms, both straight and branched, and rings of C atoms50Slide51
Examples of Carbon Compounds
51Slide52
Classifying Organic Compounds
there are two main categories of organic compounds, hydrocarbons and functionalized hydrocarbonshydrocarbons contain only C and Hmost fuels are mixtures of hydrocarbons52Slide53
Classifying Hydrocarbons
hydrocarbons containing only single bonds are called alkaneshydrocarbons containing one or more C=C double bonds are called alkeneshydrocarbons containing one or more CC triple bonds are called alkyneshydrocarbons containing C6 “benzene” ring are called aromatic53Slide54
54Slide55
Naming Straight Chain Hydrocarbons
consists of a base name to indicate the number of carbons in the chain, with a suffix to indicate the class and position of multiple bondssuffix –ane for alkane, –ene for alkene, –yne for alkyne55Base Name
No. of C
Base Name
No. of C
meth-
1
hex-
6
eth-
2
hept-
7
prop-
3
oct-
8
but-
4
non-
9
pent-
5
dec-
10Slide56
Functionalized Hydrocarbons
functional groups are non-carbon groups that are on the molecule substitute one or more functional groups replacing H’s on the hydrocarbon chaingenerally, the chemical reactions of the compound are determined by the kinds of functional groups on the molecule56Slide57
Functional Groups
57Slide58
Chemical Reactions: Equations
Writing chemical equations58The reactants (consumed; left side of reaction) are starting substances in a chemical reaction. The arrow means “yields.” The formulas on the right side of the arrow represent the products (
produced)
.
A
chemical equation
is the symbolic representation of a chemical reaction in terms of chemical formulas.
For example, the burning of sodium and chlorine to produce sodium chloride is written
Reactants (consumed)
Products (produced)Slide59
Chemical Reactions: Equations
Writing chemical equations59In many cases, it is useful to indicate the states of the substances in the equation (s, g, l, aq).
When you use these labels, the previous equation becomes
We write above the arrow any conditions for the reaction such as pressure, catalyst, heat, etc. A reaction gives a recipe for the amount of reactants needed to produce the amount of products. Species with no coefficient have an understood coefficient of 1.Slide60
Chemical Reactions: Equations
Writing chemical equations60The law of conservation of mass dictates that the total number of atoms of each element on both sides of a chemical equation must match. The equation is then said to be balanced.
2
2
We must have the same number of atoms on both sides for a reaction to be considered balanced and obeying the law of conservation of mass. To balance a reaction:
First, balance the atoms for elements that occur in only one substance on each side of the reaction. In this problem, O is involved with two substances on the product side; therefore, I will wait on balancing O until later. C & H are only in one species on both sides so I will balance them first. C needs no changes because there are one on each side, but H needs a
2
in front of H
2
O to balance the 4H on the reactants side.
Now that we have changed the coefficient of one of the O on the product side, it is easier to balance the O. We determine that we need a
2
coefficient on the O
2
to balance the O on both sides at 4. Now the equation is balanced with 1C, 4O, and 4H on both sides.Slide61
Chemical Reactions: Equations
61
Fe
2
(SO
4
)
3: has 2-Fe, 3x1 = 3-S, 3x4 = 12-OCaution: For formulas that have subscripts, you must account for all atoms especially when dealing with parentheses for polyatomic species. For example,
Caution: Remember that you can’t change the subscripts in formulas to balance equations; you may only change coefficients. If you change the subscripts, you are changing the substance.Slide62
Chemical Reactions: Equations
62
HW
19
2
2
6
6
3
2
[
]
2
2
Technique to handle odd numbers: determine number needed and divide by subscript of species. Next, you multiple the entire equation by the subscript to obtain whole numbers.
code:
balance