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slide1

Topic 2

Atoms, Elements, Molecules, Ions, and Compounds

Early in the 19th 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.

atomic theory of matter
Atomic Theory of Matter

Protons, neutrons, electrons

Later found indivisible to be untrue.

  • Postulates of Dalton’s Atomic Theory

1.)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.

Later found all atoms of the same element does not have to have the same mass.

Atoms have different isotopes that have the same # protons but different # neutrons and hence different mass. Note: #protons gives identity of atom.

atomic theory of matter1
Atomic Theory of Matter
  • Postulates of Dalton’s Atomic Theory
  • 3.) 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.
atomic theory of matter2
Atomic Theory of Matter

i.e., solid sodium mixed with chlorine gas forms a new substance, salt, with totally different properties from the starting materials.

  • Postulates of Dalton’s Atomic Theory
  • 4.) 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) + Cl2(g)

2 NaCl (s)

2

Once again, later found indivisible to be untrue.

Protons, neutrons, electrons

atomic theory of matter3
Atomic Theory of Matter
  • The Structure of the Atom
  • Although 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.”
atomic theory of matter4
Atomic Theory of Matter
  • These 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, andone or more electrons.
  • Electrons are very light, negatively charged particles that exist in the region around the atom’s positively charged nucleus.

Nucleus

(+)

e-

atomic theory of matter5
Atomic Theory of Matter
  • In 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, me, to its electric charge, e.
atomic theory of matter6
Atomic Theory of Matter
  • In 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.
atomic theory of matter7
Atomic Theory of Matter

The nuclear model of the atom.

  • Ernest 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.
atomic theory of matter8
Atomic Theory of Matter
  • Most 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.
atomic theory of matter9
Atomic Theory of Matter
  • A 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.

H Z=1 1p, 1e-

neutral species: #p = #e-

Na Z=11 11p, 11e-

Cl Z=17 17p, 17e-

Na+ Z=11 11p, 10e-

Cl- Z=17 17p, 18e-

+ charge, more p than e-

- charge, more e- than p

#p remains constant in species;

#e- can vary and dictates the charge of species

atomic theory of matter10
Atomic Theory of Matter
  • An 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:
slide13

The mass number (A) is the total number of protons and neutronsin a nucleus.

A = #p + #n = Z + #n

How many neutrons does sodium 23 have?

A = 23, Z = 11(number on periodic table)

#n = 23 - 11 = 12

A = Z + #n

23 = 11 + #n

  • 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.

+

11p, 12 n, 11e-

11p, 12 n, 10e-

slide14

What’s the element?

17 p  atomic number on periodic table for chorine

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

A = #p + #n = 17 + 18 = 35

Note: #e- = #p; therefore, neutral species

35 p

45 n

36 e-

A = #p + #n

35e- + one additional e- based on -1 charge = 36 e-

80 = 35 + #n

#n = 80 – 35 = 45 n

code for both:proton

HW 9

HW 10

Note: #e- > #p;

therefore, negatively charged species

atomic theory of matter11
Atomic Theory of Matter
  • Isotopesare 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.

Frac abund = 24.229%

Mass = 36.97 amu

Frac abund = 75.771%

Mass = 34.97 amu

17p, 20 n, 17e-

  • The fractional abundanceis the fraction of a sample of atoms that is composed of a particular isotope.

17p, 18 n, 17e-

(0.75771)(34.97 amu) + (0.24229) (36.97 amu) = 35.45 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.

atomic weights
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%)

Note: fractional abundances must add to 1 (100%)

B-10: 10.013 amu x 0.1978 = 1.980

B-11: 11.009 amu x 0.8022 = 8.831

10.811 = 10.811 amu

( = atomic wt.)

Note: mass on periodic table matches 10.811 amu (weighted average of isotopes)

code: amu

HW 11

atomic weights1
Atomic Weights

Dalton’s Relative Atomic Masses

  • Since 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).
atomic weights2
Atomic Weights

Dalton’s Relative Atomic Masses

  • Dalton’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 weightof 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 sodium

the periodic table
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.

  • periodic 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.
the periodic table1
The Periodic Table

Periods and Groups

  • A 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.
the periodic table2
The Periodic Table
  • Periods and Groups
  • The “B” groups are called transitionelements.
  • 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).
the periodic table3
The Periodic Table
  • The elements in group IA (except H) - alkali metals
  • Periods and Groups
  • The elements in group IIA - alkaline earth metals,
  • The group VIIA elements - halogens
  • The group VIIIA elements – noble gases (monoatomic)
  • Diatomic elements – H2, N2, O2, F2, Cl2, Br2, I2
  • Most species are solids at room temperature; H2, N2, O2, F2, Cl2, and noble gases are gases; Br2 and Hg are liquids.
slide24

Metals, Nonmetals, and Metalloids – generally, left of staircaseare metals, touching staircase are metalloids, right of staircase are nonmetals. This is important for determining bond type, using proper terminology, and making decisions.

Metallic character

HW 12

nonmetals

Metallic character

metals

code:

table

chemical formulas molecular and ionic substances
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.

  • aluminum oxide, Al2O3 2Al:3O ratio
  • sodium chloride, NaCl 1Na:1Cl ratio
  • calcium nitrate, Ca(NO3)2 1Ca:2NO3- ratio
  • or1Ca:2N:6O ratio
chemical formulas molecular and ionic substances1
Chemical Formulas; Molecular and Ionic Substances

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-

  • Molecular substances
  • A molecule is a definite group of atoms that are chemically bonded together through sharing of electrons (covalent bonding, generally nonmetal-nonmetal including H).
  • 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 formulasshow how the atoms are bonded to one another in a molecule.
  • i.e. ethanol (C2H6O) has a structural formula of CH3CH2OH
slide27

Although many substances are molecular, others are composed of ions (charged particles) thathavetransferred electrons and have ionic bonding; occurs generally with metal-nonmetalinteractions.

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-

chemical formulas molecular and ionic substances2
Chemical Formulas; Molecular and Ionic Substances

Ionic substances

  • The formula of an ionic compound is written by giving the smallest possible whole-number ratio of different ions in the substance.
  • The formula unit of the substance is the group of atoms or ions explicitly symbolized by its formula.

C : O

Na+Cl-

slide29

When an atom gains extra electrons, it becomes a negatively charged ion, called an anion (more electrons than protons). i.e, Cl-

  • 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
  • CaBr2
  • Na2SO4
  • CO2

Ionic substances

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 SO42-

molecular substance; molecule; covalent bonds

ions in aqueous solution
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 particles

ions in aqueous solution1
Ions in Aqueous Solution

Most molecular (covalent bond/nm-nm) compounds dissolve but do not dissociate into ions, exception acids.

C6H12O6 (s)  C6H12O6 (aq)

These compounds are referred to as nonelectrolytes; no charged particles; soluble to saturation point but no ions formed.

no charges particles; remains whole

How would sodium sulfate dissolve based on bonding?

Na2SO4 (s) 

2Na+(aq) + SO42-(aq)

ionic bond dissociates while covalent bonds in sulfate remain intact

chemical substances formulas and names
Chemical Substances; Formulas and Names

Ionic compounds

  • Most ionic compounds contain metal and nonmetal atoms (as well as polyatomic ions); for example, NaCl.
  • 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, CaI2
  • Potassium Bromide, 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

Most of the main group metals form cations with the charge equal to their roman group number.

  • 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 charge
  • Pb4+, Pb2+ Sn4+, Sn2+ As5+, As3+ Sb5+, Sb3+

How do we get the charge for ions?

Rules for predicting charges on monatomic ions

0

1+

4-

2+

3+

4+

3-

2-

1-

varies

slide34

Monatomic cations are named after the element. For example, Al3+ is called the aluminum ion.

  • 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 ion
  • Fe2+ iron (II) ion Fe3+ iron (III) ion
  • Older name: higher ox state (charge) – ic, / lower, -ous
  • Fe3+ferric ion Fe2+ferrous ion Cu2+cupric ion
  • Cu+ cuprous ion Hg2+mercuric ion Hg22+mercurousion
  • also done with Pb4+, Pb2+; Sn4+, Sn2+; As5+, As3+; Sb5+, Sb3+.
  • For the names of the monatomic anions, use the stem name of the element followed by the suffix – ide. For example bromine, the anion is called bromide ion, Br-.

Rules for naming monatomic ions

slide35

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.

formula

ions and charges

NaCl

Roman number tells charge of transition metal

1Na+= 1+ charge

1Cl- = 1- charge

balanced

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 Sr2+ O2-

Fe2(SO4)3

2 3

2Fe3+ = 6+ charge

3SO42- = 6- charge

balanced

Cr2O3

Ca(NO3)2

Generally, you can crisscross the charge of one ion as the subscript on the second ion, reducing when possible.

Na3PO4

HW 13 & 14

code for both: formula

SrO

naming ionic binary compounds
Naming Ionic Binary Compounds

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.

sodium fluoride

NaF -

- lithium chloride

MgO -

MnBr2 -

- cobalt (III) oxide

- copper (II) chloride or cupric chloride

LiCl

magnesium oxide

The charge on Mn must be 2+ to balance out the 2Br- charges.

manganese (II) bromide

The Roman number 3 tells us the charge on Co is 3+ which helps us determine the formula knowing that O is 2-.

Co2O3

CuCl2

chemical substances formulas and names1
Chemical Substances; Formulas and Names
  • A polyatomic ionis 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).

Polyatomic ions

NO3- nitrate SO42- sulfate

NO2- nitrite SO32- sulfite

Most groups have –ate, -iteendings and differ by #O.

Mn, Br, Cl, I have per- -ate, -ate, -ite, hypo- -ite.

ions you should know
O22- - Peroxide

PO43- - Phosphate

PO33- - Phosphite

CO32- - Carbonate

HCO3- - Bicarbonate or Hydrogen Carbonate

N3- - azide

NO3- - nitrate

NO2- - nitrite

C2H3O2-or CH3COO-- acetate

Cr2O72- - dichromate

CrO42- - chromate

C2O42- - oxalate

HSO4- - bisulfate or hydrogen sulfate

H2PO4- - dihydrogen phosphate

Ions You Should Know

Polyatomic ions

  • NH4+ - Ammonium
  • OH- - Hydroxide
  • CN- - Cyanide
  • SO42- - Sulfate
  • SO32- - Sulfite
  • ClO4- - perchlorate
  • ClO3- - chlorate
  • ClO2- - chlorite
  • ClO- - hypochlorite
  • Hg22+ - mercury (I) or mecurous
  • S2O32- - thiosulfate
  • SCN- - thiocyanate
  • CNO- - cyanate
  • MnO4- - permanganate
slide39

tin (II) sulfate or stannous sulfate

Na2SO3

calcium hypochlorite

SnSO4

sodium sulfite

Ca(ClO)2

barium hydroxide

potassium perchlorate

Cr2(SO4)3

magnesium nitride

Fe3(PO4)2

titanium (IV) nitrate

Ba(OH)2

KClO4

chromium (III) sulfate

Note: Not a polyatomic ion; monoatomic anion of N.

Mg3N2

iron (II) phosphate or ferrous phosphate

Ti(NO3)4

chemical substances formulas and names2
Chemical Substances; Formulas and Names

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?

NF3 F3N

chemical substances formulas and names3
Chemical Substances; Formulas and Names

Binary molecular compounds

  • The name of the compound has the elements in the order given in the formula.
  • 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.)
slide42

N2O3

  • SF4
  • chlorine dioxide
  • sulfur hexafluoride
  • Cl2O7
  • HCl (g)
  • Name this compound but think about bonding:
  • MgCl2
  • Older names: water - H2O, ammonia – NH3,
  • hydrogen sulfide – H2S, nitric oxide – NO, hydrazine – N2H4

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.

dinitrogen trioxide

sulfur tetrafluoride

  • Binary molecular compounds

ClO2

SF6

Drop the “a” on prefix if you encounter double vowel in name.

dichlorineheptoxide

Since this is a gas, we name using molecular rules; however, if acid we have other rules.

hydrogen chloride

magnesium chloride; ionic comp, no prefix

chemical substances formulas and names4
Chemical Substances; Formulas and Names

Acids

  • Acids are traditionally defined as compounds with a potential H+ as the cation.
  • Binary acids consist of a hydrogen ion and any single anion in aqueous solution. For example, HCl (aq) is hydrochloric acid. Binary acid: hydrostemicacid
  • An oxoacidis 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.
slide44

If you learn the oxoanions, you can easily adapt to naming the oxoacids:

-ate  -ic and –ite  -ous

oxoacids

Anion prefix/suffixacid 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 acid

NO2- nitrite ion HNO2 nitrous acid

ClO4- perchlorate ion HClO4perchloric acid

For some species there is a change in spelling in the name.

SO42- sulfate ion H2SO4 sulfuric acid

PO43- phosphateion H3PO4 phosphoric acid

chemical substances formulas and names5
Chemical Substances; Formulas and Names
  • A hydrateis a compound that contains water molecules weakly bound in its crystals.

Hydrates

  • 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.
  • CuSO4. 5H2O
  • Magnesium sulfate heptahydrate

copper(II)sulfate pentahydrate

MgSO4.7H2O

HW 15 - 18

code for all: names

chemical substances formulas and names6
Chemical Substances; Formulas and Names

Naming simple compounds

  • Chemical 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.
chemical formulas molecular and ionic substances3
Chemical Formulas; Molecular and Ionic Substances

Organic compounds

  • An 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, C2H6, and propane, C3H8.
classifying compounds organic vs inorganic
Classifying CompoundsOrganic vs. Inorganic
  • in the 18th century, compounds from living things were called organic; compounds from the nonliving environment were called inorganic
  • organic compounds easily decomposed and could not be made in 18th century lab
  • inorganic compounds very difficult to decompose, but able to be synthesized
modern classifying compounds organic vs inorganic
Modern Classifying CompoundsOrganic vs. Inorganic
  • today we commonly make organic compounds in the lab and find them all around us
  • organic compounds are mainly made of C and H, sometimes with O, N, P, S, and trace amounts of other elements
  • the main element that is the focus of organic chemistry is carbon
carbon bonding
Carbon Bonding
  • carbon atoms bond almost exclusively covalently
    • compounds with ionic bonding C are generally inorganic
  • when C bonds, it forms 4 covalent bonds
    • 4 single, 1 double + 2 singles, 2 double, or 1 triple + 1 single
    • carbon is unique in that it can form limitless chains of C atoms, both straight and branched, and rings of C atoms
classifying organic compounds
Classifying Organic Compounds
  • there are two main categories of organic compounds, hydrocarbons and functionalized hydrocarbons
  • hydrocarbons contain

only C and H

  • most fuels are mixtures of hydrocarbons
classifying hydrocarbons
Classifying Hydrocarbons
  • hydrocarbons containing only single bonds are called alkanes
  • hydrocarbons containing one or more C=C double bonds are called alkenes
  • hydrocarbons containing one or more CC triple bonds are called alkynes
  • hydrocarbons containing C6 “benzene” ring are called aromatic
naming straight chain hydrocarbons
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 bonds
    • suffix –ane for alkane, –ene for alkene, –yne for alkyne
functionalized hydrocarbons
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 chain
  • generally, the chemical reactions of the compound are determined by the kinds of functional groups on the molecule
chemical reactions equations
Chemical Reactions: Equations
  • A chemical equation is the symbolic representation of a chemical reaction in terms of chemical formulas.

Writing chemical equations

  • For example, the burning of sodium and chlorine to produce sodium chloride is written
  • The 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).

Products (produced)

Reactants (consumed) 

chemical reactions equations1
Chemical Reactions: Equations

Writing chemical equations

  • In 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.

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Chemical Reactions: Equations
  • The law of conservation of massdictates 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.

Writing chemical equations

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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 H2O 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 O2 to balance the O on both sides at 4. Now the equation is balanced with 1C, 4O, and 4H on both sides.

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Chemical Reactions: Equations

Caution: For formulas that have subscripts, you must account for all atoms especially when dealing with parentheses for polyatomic species.

For example,

Fe2(SO4)3: has 2-Fe, 3x1 = 3-S, 3x4 = 12-O

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.

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Chemical Reactions: Equations

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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.

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code: balance

HW 19