The Components of Matter

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The Components of MatterThe Components of Matter

ChapterChapter 2 2


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MATTER

PURE SUBSTANCES MIXTURES

ELEMENTS COMPOUNDS HOMOGENOUS

HETEROGENEOUSComposed only of atoms of the same element.

Two or more elements

chemically combined.

(See definitions in slide after next.)


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Compound - a substance

composed of two or more elements

which are chemically combined.

Mixture - a group of two or more elements and/or compounds which are physically intermingled.

Definitions for Components of Matter

Figure 2.1


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Allowed to react chemically therefore cannot be separated by physical means.

Figure 2.19

The distinction between mixtures and compounds.

S

Fe

Physically mixed therefore can be separated by physical means; in this case by a magnet.

MIXTURE COMPOUND


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Mixtures

Heterogeneous mixtures : have one or more visible boundaries between the components. Ex: water and oil

Homogeneous mixtures : have no visible boundaries because the components are mixed as individual atoms, ions, and molecules.Ex: water and dissolved salt.

Solutions : A homogeneous mixture is also called a solution. Solutions in water are called aqueous solutions, and are very important in chemistry. Although we normally think of solutions as liquids, they can exist in all three physical states.


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Filtration : Separates components of a mixture based upon differences in particle size. Normally separating a precipitate from a solution, or particles from an air stream.

Crystallization : Separation is based upon differences in solubility of components in a mixture.

Distillation : separation is based upon differences in volatility.

Extraction : Separation is based upon differences in solubility in different solvents (major material).

Chromatography : Separation is based upon differences in solubility in a solvent versus a stationary phase.

Basic Separation Techniques

Tools of the Laboratory


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Basic Separation Techniques

Figure B2.3 Filtration Figure B2.4 Crystallization

From full-size Silberberg text


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Physical Properties: color, texture, odor, density, BP, MP, etc.

Chemical Properties: how a substance reacts with other substances


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Chemical

Physical properties: MP, BP, color, density, solubility in water. (*Except Na reacts with water.)

PhysicalProperties*:


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Identify the type of matter in four ways: element, compound, homogenous mixture, or heterogeneous mixture

Know the three states of matter Separate physical properties from chemical

properties


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The total mass of substances does not change during a chemical reaction.

reactant 1 + reactant 2 product

total mass total mass=

calcium oxide + carbon dioxide calcium carbonate

CaO + CO2CaCO3

56.08g + 44.00g 100.08g

Law of Mass Conservation:


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No matter the source, a particular compound is composed of the same elements in the same parts (fractions) by mass.

Calcium carbonate Calcium carbonate

Analysis by MassAnalysis by Mass(grams/20.0g)(grams/20.0g)

Mass FractionMass Fraction(parts/1.00 part)(parts/1.00 part)

Percent by MassPercent by Mass(parts/100 parts)(parts/100 parts)

8.0 g calcium8.0 g calcium2.4 g carbon2.4 g carbon9.6 g oxygen 9.6 g oxygen

20.0 g20.0 g

40% calcium40% calcium12% carbon12% carbon48% oxygen 48% oxygen

100% by mass100% by mass

0.40 calcium0.40 calcium0.12 carbon0.12 carbon0.48 oxygen 0.48 oxygen

1.00 part by mass1.00 part by mass

Law of Definite (or Constant) Composition:

Figure 2.3 (4th ed.)


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If elements A and B react to form two compounds, the different masses of B that combine with a fixed mass of A can be expressed as a ratio of small whole numbers.

Example: There are two “Carbon Oxides,” A & BCarbon Oxide I : 57.1% oxygen and 42.9% carbonCarbon Oxide II : 72.7% oxygen and 27.3% carbon

Assume that you have 100 g of each compound. That means that Oxide I has 57.1 g of oxygen and 42. 9 g of carbon; Oxide II has 72.7 g of oxygen and 27.3 g of carbon.

g O

g C=

57.1

42.9= 1.33

= g O

g C

72.7

27.3= 2.66

2.66 g O/g C in II

1.33 g O/g C in I

2

1=

Law of Multiple Proportions:


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Dalton’s Atomic Theory (MEMORIZE!) Dalton’s Atomic Theory (MEMORIZE!)

1. All matter consists of atoms.

2. Atoms of one element cannot be converted into atoms of another element.

3. Atoms of an element are identical in mass and other properties and are different from atoms of any other element.

4. Compounds result from the chemical combination of a specific ratio of atoms of different elements.


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Fig 2.4 Experiments to Determine the Properties of Cathode Rays

OBSERVATION

1. Ray bends in magnetic field.

2. Ray bends towards positive plate in electric field.

CONCLUSION

consists of charged particles

consists of negative particles3. Ray is identical for any cathode.

particles found in all matter

This led to the discovery of Electrons.


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Figure 2.5 Millikan’s oil-drop experiment

for measuring an electron’s charge.

(1909)(1909)


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Millikan used his findings to also calculate the mass of an electron.

mass of electron =mass

chargeX

charge

= (-5.686x10-12 kg/C) X (-1.602x10-19 C)

determined by J.J. Thomson and others

= 9.109x10-31 kg = 9.109x10-28 g


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At the beginning of the 20th Century: scientists knew an atom contained both positive and negative particles. One model was “plum pudding” – like raisins in rice pudding.

Rutherford’s experiment showed that an alpha particle (a Helium nucleus with 2 protons and 2 neutrons) aimed at gold foil was deflected almost straight back. NOT WHAT HE EXPECTED: HAD TO REVISE THEIR MODEL!!!

Led to modern nuclear atom model.


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Figure 2.6


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Figure 2.7 General features of the nuclear atom (Know these!)

Atom is electrically neutral, spherical & composed of a positively charged central nucleus surrounded by one or more negatively charge electrons.

Nucleus consists of protons and neutrons.


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Properties of the Three Key Subatomic Particles

Charge Mass

Relative

1+

0

1-

Absolute(C)*

+1.60218x10-19

0

-1.60218x10-19

Relative(amu)†

1.00727

1.00866

0.00054858

Absolute(g)

1.67262x10-24

1.67493x10-24

9.10939x10-28

Location in the Atom

Nucleus

Outside Nucleus

Nucleus

Name(Symbol)

Electron (e-)

Neutron (n0)

Proton (p+)

Table 2.2

* The coulomb (C) is the SI unit of charge.

† The atomic mass unit (amu) equals 1.66054x10-24 g.

You memorize what’s boxed above.


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From Figure 2.8

Atomic Symbols, Isotopes, Numbers

X = Atomic symbol of the element

A = mass number; A = Z + N

Isotope = atoms of an element with the same number of protons, but a different number of neutrons

A

Z

Z = atomic number (the number of protons in the nucleus)

N = number of neutrons in the nucleus

X The Symbol of the Atom or Isotope


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Sample Problem 2.4 Determining the Number of Subatomic Particles in the Isotopes of an Element

PROBLEM: Silicon has three naturally occurring isotopes: 28Si, 29Si, and 30Si. Determine the number of protons, neutrons, and electrons in each silicon isotope.

SOLUTION: The atomic number of silicon is 14. Therefore

28Si has 14p+, 14e- and 14n0 (28-14)

29Si has 14p+, 14e- and 15n0 (29-14)

30Si has 14p+, 14e- and 16n0 (30-14)

Now you try these uranium isotopes: 234, 235, 238, and 239.


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REMEMBER: In an atom of the same element

# protons never changes (except for nuclear decay)

# neutrons can be different ISOTOPES

# electrons can change IONS


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Figure B2.2The Mass Spectrometer and Its DataThe Mass Spectrometer and Its DataTools of the Laboratory

2.9


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Fig 2.9 is a simple schematic, but the mass spec determines the actual mass of each isotope to many sig figs and its percent abundance, usually to six or more sig figs.

Chart B = the mass charge ratio, which determines the mass to many sig figs (look at fluorine on per table)

Chart C = a count of each isotope which is reported as percent abundance, again to many sig figs

By using a mass spectrometer, an atom’s isotopes can be counted, establishing relative abundance of each isotope and its exact mass. From this data we can calculate a weighted average atomic mass:

Weighted average atomic mass = fract1*mass1 + fract2*mass2 + ...


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We put boron in a mass spectrometer, and find there are just two isotopes, with these results: 19.91% Boron-10 with mass 10.0129 amu and 80.09% Boron-11 mass with11.0093 amu

Average atomic mass = (0.1991 * 10.0129) + (0.8009 * 11.0093)

= 1.994 + 8.817 = 10.811 (sig fig rules)

Do problem 33 for practice on this method. (Magnesium has three naturally occurring isotopes. 24Mg has a mass of 23.9850 amu and 78.99% abundance, 25Mg has a mass of 24.9868 amu and 10.00% abundance, and 26Mg has a mass of 25.9826 amu and 11.01% abundance.)


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You have just practiced determining the weighted average atomic mass. How is that different from mass number?

ATOMIC MASS IS NOT THE SAME AS MASS NUMBER!ATOMIC MASS IS NOT THE SAME AS MASS NUMBER!ATOMIC MASS IS NOT THE SAME AS MASS NUMBER!

Think you can remember this?


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The Modern Reassessment of the Atomic Theory

1. All matter is composed of atoms. The atom is the smallest body that retains the unique identity of the element.

2. Atoms of one element cannot be converted into atoms of another element in a chemical reaction. Elements can only be converted into other elements in nuclear reactions.

3. All atoms of an element have the same number of protons and electrons, which determines the chemical behavior of the element. Isotopes of an element differ in the number of neutrons, and thus in mass number. A sample of the element is treated as though its atoms have an average mass.

4. Compounds are formed by the chemical combination of two or more elements in specific ratios.


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Figure 2.10 The modern periodic table.The modern periodic table.


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Write down group names, locations for metal, nonmetals and metalloids.

(Alkali metals, alkaline earth metals, halogens, noble gases, metalloids along stairs, metals to lower left, nonmetals to upper right)

What trends do you know?(Fr is largest, He is smallest)Where are the transition metals and the inner

transition metals?(Be able to locate them.)


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You need to memorize the first 36 elements’ symbols and names, plus ten more: Ag, Sn, I, Ba, Pt, Au, Hg, Pb, Rn, and U.


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Figure 2.11 from 4th ed. Metals, metalloids, and nonmetals.

Chromium

CopperCadmium

Lead

Bismuth

Boron

Silicon

Arsenic

Antimony

TelluriumCarbon(graphite)

Sulfur

Chlorine Bromine

Iodine

Stop here and go to chapter 7!


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Figure 2.14 from 4th ed.

The relationship between ions formed and the nearest noble gas.


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Formation of a covalent bond between two H atoms.Figure 2.13

Covalent bonds form when elements share electrons, which usually occurs between nonmetals.


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Use the lecture notes, the textbook AND the lab manual’s Dry Lab on Nomenclature.

All the tables in the dry lab will be very useful!


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The seven common diatomic elements: H2, O2, N2, F2, Cl2, Br2, I2

(Memory aid: HON+Halogens)


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Types of Chemical Formulas

An empirical formula indicates the relative number of atoms of each element in the compound. It is the simplest type of formula.

A molecular formula shows the actual number of atoms of each element in a molecule of the compound.

A structural formula shows the number of atoms and the bonds between them, that is, the relative placement and connections of atoms in the molecule.

A chemical formula is comprised of element symbols and numerical subscripts that show the type and number of each atom present in the smallest unit of the substance.

The empirical formula for hydrogen peroxide is HO.

The molecular formula for hydrogen peroxide is H2O2.

The structural formula for hydrogen peroxide is H-O-O-H.


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Figure 2.16Figure 2.16 Some common monatomic ions of the elements.Some common monatomic ions of the elements.Can you see any patterns?

Be2+

See large Periodic Table handout for variety of charges of metals.


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Remember that metals like iron or tin with more than one possible charge have to show which one by using Roman numerals for the charge in parentheses.

Sn2+ is tin (II) ionSn4+ is tin (IV) ion


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Naming binary ionic compounds: see rules in your packet

The name of the cation is the same as the name of the metal.

Many metal names end in -ium.

The name of the anion takes the root of the nonmetal name and adds the suffix -ide.

Calcium ion and bromide ion form calcium bromide.

The name of the cation is written first, followed by that of the anion.


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EXAMPLE: Form an ionic compound of Al & Br and then Al & O.

Al forms Al3+ and Br forms Br-, so the ratio will be 1:3 or AlBr3 aluminum bromide.

Again, Al forms Al3+ and O forms O2-, so the ratio will be 2:3 or Al2O3 aluminum oxide.

Special trick called the criss-cross rule: Xa+ & Yb- XbYa but if b=a, reduce formula to 1:1 ratio (unless mercury (I) ion is involved)


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Naming Binary Ionic Compounds (sample problems 2.7 & 2.8

PROBLEM: Write formulas and name the ionic compound formed from the following pairs of elements:

(a) magnesium and nitrogen

SOLUTION:

(b) iodine and cadmium(c) strontium and fluorine (d) sulfur and cesium

(a) Mg2+ & N3-; three Mg2+(6+) & two N3-(6-); Mg3N2

magnesium nitride(b) Cd2+ & I-; one Cd2+(2+) & two I-(2-); CdI2

cadmium iodide(c) Sr2+ & F-; one Sr2+(2+) & two F-(2-); SrF2

strontium fluoride(d) Cs+ & S2-; two Cs+(2+) and one S2- (2-); Cs2S

cesium sulfide

Now do the follow-up problems.


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Sample Problem 2.9 Determining Names and Formulas of Ionic Compounds of Elements That Form More Than One Ion

SOLUTION:

PROBLEM: Give the systematic names for the formulas or the formulas for the names of the following compounds:

(a) tin(II) fluoride (b) CrI3

(c) Iron (III) oxide (d) CoS

(a) Tin (II) is Sn2+; fluoride is F-; so the formula is SnF2.

(b) The anion I is iodide(I-); 3I- means that Cr(chromium) is +3. CrI3 is chromium(III) iodide

(c) Iron (III) is the name for Fe3+; oxide is O2-, therefore the formula is Fe2O3.

(d) Co is cobalt; the anion S is sulfide(2-) so cobalt must be +2; the compound is cobalt (II) sulfide.


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Hydrates are ionic crystals of salts with water molecules incorporated in their crystal structures.

Write "formula unit name - dash - Greek prefix (representing # of water molecules) hydrate"

BaCl2.2H2O is barium chloride dihydrate

You try: Name CuSO4

.5H2O:

Give the formula for sodium sulfate decahydrate:


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Naming oxoanions

Prefixes Root Suffixes Examples

rootper ate ClO4- perchlorate

ateroot ClO3- chlorate

iteroot ClO2- chlorite

itehypo root ClO- hypochlorite

No

. of

O a

tom

sFigure 2.17

Numerical Prefixes for Hydrates and Binary Covalent Compounds

Number Prefix Number Prefix Number Prefix

1 mono

2 di

3 tri

4 tetra

5 penta

6 hexa

7 hepta

8 octa

9 nona

10 deca

Table 2.6


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Sample Problem 2.10 Determining Names and Formulas of Ionic Compounds Containing Polyatomic Ions

SOLUTION:

PROBLEM: Give the systematic names or the formula or the formulas for the names of the following compounds:

(a) Fe(ClO4)2(b) sodium sulfite

(a) ClO4- is perchlorate; iron must have a 2+ charge. This is

iron(II) perchlorate.

(b) The anion sulfite is SO32- therefore you need 2 sodiums per

sulfite. The formula is Na2SO3.

(c) Hydroxide is OH- and barium is a 2+ ion. When water is included in the formula, we use the term “hydrate” and a prefix which indicates the number of waters. So it is barium hydroxide octahydrate.

(c) Ba(OH)2 8H2O


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Naming Inorganic Acids

1) Binary acid solutions form when certain gaseous compounds dissolve in water. For example, when gaseous hydrogen chloride (HCl) dissolves in water, it forms a solution called hydrochloric acid. Prefix hydro- + anion nonmetal root + suffix -ic + the word acid - hydrochloric acid

Practice naming H2S(aq):

2) Oxoacid names are similar to those of the oxoanions, except for two suffix changes:

Anion “-ate” suffix becomes an “-ic” suffix in the acid. Anion “-ite” suffix becomes an “-ous” suffix in the acid. The oxoanion prefixes “hypo-” and “per-” are retained. Thus,

BrO4-

is perbromate, and HBrO4 is perbromic acid; IO2- is iodite, and

HIO2 is iodous acid.

Practice naming HClO3:


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Sample Problem 2.12 Determining Names and Formulas of Anions and Acids

SOLUTION:

PROBLEM: Name the following anions and give the names and formulas of the acids derived from them:

(a) Br - (b) IO3 - (c) CN - (d) SO4

2- (e) NO2 -

(a) The anion is bromide; the acid is hydrobromic acid, HBr.

(b) The anion is iodate; the acid is iodic acid, HIO3.

(c) The anion is cyanide; the acid is hydrocyanic acid, HCN.

(d) The anion is sulfate; the acid is sulfuric acid, H2SO4.

(e) The anion is nitrite; the acid is nitrous acid, HNO2.


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Very simple – you will know a compound is covalent if it's two nonmetals. Indicate how many of each atom in the compounds by using Greek prefix (mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca)

If first element is single, leave off mono. If first element is hydrogen, leave off any prefix.

‘Prefix'element name - 'prefix'element root - suffix 'ide'

Practice: CO, CO2, NO2, N2O4, P2O5, HF, H2S


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We still use old common names you'll have to memorize:

water H2O hydrogen peroxide H2O2

Ammonia NH3

Blood sugarTable sugar


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Learning the rules for naming organic compounds would take a month or more!

Just memorize these:Methane CH4 Ethane CH3CH3

Propane CH3CH2CH3 Butane CH3(CH2)2CH3

Octane CH3(CH2)6CH3 Benzene C6H6

Acetylene C2H2

Methanol CH3OH Ethanol CH3CH2OH1-Propanol CH3CH2CH2OHAcetic Acid CH3COOH Formaldehyde HCHOGlucose C6H12O6 Sucrose C12H22O11


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Look up the molar mass on the Periodic Table. Sum up all atoms in the compound.

(This part goes just before or with chapter 3.)


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Sample Problem 2.15 Calculating the Molecular Mass of a Compound

SOLUTION:

(a) tetraphosphorous trisulfide (b) ammonium nitrate

PROBLEM: Using the data in the periodic table, calculate the molecular (or formula) mass of the following compounds:

PLAN: Write the formula and then multiply the number of atoms(in the subscript) by the respective atomic masses. Add the masses for the compound.

(a) P4S3

molecular mass

= (4x atomic mass of P)

+ (3x atomic mass of S)

= (4x30.97 amu) + (3x32.07 amu)

= 220.09 amu

(b) NH4NO3

molecular mass

= (2x atomic mass of N)

+ (4x atomic mass of H)

+ (3x atomic mass of O) = (2x14.01 amu)+ (4x1.008 amu)

+ (3x16.00 amu)

= 80.05amu


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Do the follow-up problem for 2.15 in text:Determine the formula and the molecular (or

formula) mass for each of these:a. hydrogen peroxideb. cesium chloridec. sulfuric acidd. potassium sulfate

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The Components of Matter

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