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Chapter 1: Fundamentals

Textbook chapter 3

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•Introduction to matter•Properties of matter

•Physical and chemical properties•Extensive and intensive properties•Temperature and density

•Composition of the atom•Atomic model•Atomic mass•Isotopes

•The periodic table and periodicity of elements’ properties•Naming molecular and ionic substances•The mole and molar mass•Percent composition

Outline

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Introduction to Matter• Physical material of the universe

• Anything that occupies space and has mass• Exists in three physical states (solid, liquid, gas)

• Matter is made up of atoms

Atom: Basic unit of any chemical element

Element:• substance made up of atoms of the same kind (same atomic number)• Represented by symbols of 1 or 2 letters (Co, Cu, H, O, …)• To date: 118 elements (periodic table)•Allotropes are two or more distinct forms of an element (O, O2, O3)

Sodium Metal

Chlorine Gas

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Introduction to Matter•Compound: substance made up of atoms of 2 or more elements chemically united (H2O, CO2, NaCl, …)

• Substance: a form of matter (element or compound) having a fixed composition and distinct identity (water, iron, glucose, …)

• Mixture:• Combination of 2 or more substances (tea, salted water, vinegar, mixture of sand + iron filling, air, …)•Homogenous mixture (or solution): composition is uniform throughout the sample (salted water, tea …)•Heterogeneous mixture: composition is not uniform throughout the sample (sand + iron filling, water + sand, …)

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ChemistryStudy of elements composing matter and the changes they

undergo(Composition, Characteristics, Reactions)

Sodium Metal Chlorine Gas Sodium Reacting with

Chlorine

Crystals ofSodium Chloride

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Chemists Interact with Others

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Physical and Chemical Properties of matter

• Physical property:•Can be measured without changing the identity

color, melting point, boiling point, optical density….

• Chemical property (reactivity): •Describes the way a substance may change into another

CH4 + 2O2 → CO2 + 2H2O

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Extensive and intensive properties

• Extensive property:Is additive depends on the amount of matter

mass, volume, length, …

• Intensive property:

Not additive does not depend on the amount of matter

density, concentration, pressure, viscosity, melting point, …

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TemperatureA measure of the motion of particles in a system

Three systems for measuring the temperature:

• The Celsius scale (oC):

•under 1 atm: zero is the freezing point and 100 is the boiling point of water

•The Kelvin scale (K):

•Zero is the lowest temperature that can be attained theoretically = - 273.15oC Tk = TC + 273.15

Celsius and Kelvin scales have the same degree size but differ in the zero point.

• Remark:The Fahreinheit scale: under 1 atm:32 is freezing point of water; 212: boiling point of water (TF = (TC x 9/5) + 32)

Used in engineering sciencesDiffers from the Celsius and Kelvin scale in the zero point and in the degree size

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Density

The mass of a substance per unit of volume of the substance: d = m/V

Unit: g/cm3 or (g/L for gases)

Remark: The mass of an object is measured by comparing it to a standard mass of 1 kg, which is the basic SI unit for mass.1 kg is the mass of I liter of water at 4oC.The weight is a measure of the gravitational force (pull) on a given mass by the gravity.

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Atoms

“Atomos” = Indivisible Definition: the smallest particle of an element that retains the properties of that element

Modern theory assumptions of the atom (John Dalton, in 1803)1. Matter is made up of atoms that are indivisible and indestructible2. All atoms of a given element are identical3. Atoms of different elements combine in simple whole numbers

to form compounds4. Atoms of different elements have different weights and different

chemical properties5. Atoms cannot be created nor destroyed. When a compound

decomposes, the atoms are recovered unchanged

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Composition of the atom

An atom is composed of a nucleus (protons + neutrons) surrounded by an electronic cloud

Representation of atoms:A ------> mass number (nb of p+ + nb of no)

XZ ------> atomic number (nb of p+)

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Alpha-Particle Bombardment

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IsotopesIsotopes: atoms of a given element having the same Z but different A

Differ in the number of neutrons

e.g.: C-12 and C-13 ; H-1, H-2 and H-3

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Atomic Mass

Based on the mass of carbon: carbon-12 (the most common isotope of carbon)

C-12 is assigned a mass of exactly 12 atomic mass units (amu)

Masses of other atoms are given relative to C-12 Relative Atomic masses

Relative atomic masses are easily calculated by mass spectrometry.

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Mass Spectrometry

Finding the mass of an element:

From mass spectrometery: mass of 13C / mass of 12C = 1.0836129

So the mass of a 13C atom is: (1.0836129) (12 amu) = 13.003355 amu

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Average Atomic Mass

Elements occur in nature as mixtures of isotopes

Atomic mass is based on the relative abundance of isotopes

E.g.: carbon in nature:98.89% 12C, 1.11% 13C and <0.01% 14C (negligable)

Average atomic mass of natural carbon =(98.89 /100x 12 amu) + (1.11/100 x 13.003 amu) =

12.01 amu

The average atomic mass is often called the atomic weight

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Isotopic Composition of Ne

The mass spectrum of neon

20Ne = 0.907

22Ne = 0.09

21Ne = 0.003

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Exercise

Calculate the average atomic weight of Boron (B) from the following data:

Isotope Isotopic mass (amu) Fractional abundance10B 10.013 0.197811B 11.009 0.8022

10B = 10.013 x 0.1978 = 1.9806

11B = 11.009 x 0.8022 = 8.8314

10.812 amu

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Exercise

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The Periodic Table

Matter elements were classified according to their chemical behavior

This effort resulted in the development of the Periodic Table (1869)

Where,

Elements with similar properties fall within the same column called group or family

The horizontal rows within the periodic table are called period

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Z increases

Z increases

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Periodicity of Elements Properties

Within a group

Elements show similar chemical and physical properties

Example:Li, Na, and K are all soft, very reactive metals He, Ne, and Ar are very non-reactive gasses

ANDEach of the soft reactive metals comes immediately after one of the

nonreactive gases

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Major Groups of the Periodic Table

Group Name Elements Properties

1A Alkali metals (wood ashes) Li, Na, K, Rb, Cs, Fr Monovalent cations

2A Alkaline earth metals Be, Mg, Ca, Sr, Ba, Ra Divalent cations

6A Chalcogens ("chalk formers") O, S, Se, Te, Po Divalent anions

7A Halogens ("salt formers") F, Cl, Br, I, At Monovalent anions

8A Noble gases (rare gases) He, Ne, Ar, Kr, Xe, Rn Inert

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The Three Categories of the Periodic Table

Metals (everything on the left of the Al - Po diagonal):Good conductor of electricity and heat

Ductile and malleableLustrous

Solid at room temperature

Non-metals (to the right of the Al – Po diagonal):Poor conductor of electricity and heat

Not ductile nor malleableNon-lustrous

Metalloides (elements found along the Al – Po diagonal:(Al, Si, Ge, As, Sb, Te, Po, At):

Have properties of both metals and nonmetals

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Molecules (Molecular Substances)

• Neutral aggregates of at least two atoms• Can be diatomic (H2, N2, O2, Cl2, Br2, I2, CO, HCl…)

OrPolyatomic (H2O, CH4, N2O4, C6H12O6).

• Molecular formula shows the exact number of atoms of each element in the molecule

• Empirical formula the simplest whole number ratio of atoms Examples:Substance Molecular formula Empirical formulaWater H2O H2O

Hexane C6H14 C3H7

Glucose C6H12O6 CH2O

Ammonia NH3 NH3

• Molecules are usually composed of nonmetallic elements

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Naming Molecular Formula

• First word: name of the first element with a Greek prefix to denote the number of atoms

• Second word: Name of the second element with a Greek prefix for the number of atom and the suffix -ide attached • The prefixes are: di: 2 - tri: 3 - tetra: 4 - penta: 5 - hexa: 6 - hepta: 7 - octa: 8 – nona: 9 - deca 10 Examples:PCl5 : phosphorus pentachloride ; N2O4: dinitrogen tetroxide ; Cl2O7: dichlorine heptoxide; N2H4: dinitrogen tetrahydride

Common exceptions: CH4: methane; NH3: ammonia; H2O: water ; H2S: hydrogen sulfide

Others : B2H6: diborane ; SiH4: silane

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Ions

Atoms or groups of atoms that have a positive or negative charge

Examples:Monoatomic ions: Cl-, Na+, Mg2+…Polyatomic ions : OH-, SO4

2-, NH4+

Positively charged cationsNegatively charged anions

With very few exceptions:

metallic elements cationsNonmetallic elements anions

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Sodium Atom and Ion

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Chlorine Atom and Ion

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Naming Monoatomic Ions

Monoatomic cations: • Elements of groups 1A and 2A One ionic form (Type I): The name of the ion is the same as the name of the metal• E.g.: Na+ is sodium ion

• Transition Metals More than one ionic form (Type II) use Roman numeral.• Fe2+ is iron(II) or Ferrous ion• Fe3+ is iron(III) or Ferric ion

Monoatomic anions:• Add the suffix “ide” to the stem•E.g.: N3-: nitride ; O2-; oxide ; Cl-: chloride

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Naming Polyatomic Ions

Ions of nonmetals and oxygen:

1- If a nonmetal forms two possible anions with oxygen, the one with the largest number of oxygen has the suffix -ate attached to the root of the nonmetal. The one with the fewer number of oxygen atoms has the suffix -ite

SO42- is the sulfate ion SO3

2- is the sulfite ion

PO43- is the phosphate ion PO3

3- is the phosphite ion

2- If the nonmetal forms more than two, the prefix per- is attached to the ion with the most oxygens, the prefix hypo- to the one with the fewest

ClO4- is the perchlorate ion

ClO3- is the chlorate ion

ClO2- is the chlorite ion

ClO- is the hypochlorite ion

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Other Common Polyatomic Ions

OH-: hydroxide CN-; cyanide

SCN-: thiocyanate C2H3O2

-: acetate

CrO42-: chromate

Cr2O72-: dichromate

MnO4-: permanganate

NH4+ : Ammonium

Example: What are the names of the NO3- and NO2

- ions?

Solution: Here we have two ions that have a nonmetal (N) and oxygen. We use the root of the nonmetal, nitrogen to get nitr-, then attach a -ate to the one with

the most oxygens and a -ite to the one with the fewest NO3

-: nitrate

NO2-: nitrite

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Ionic Compounds

• Made of cations and anions attracted to each other

• Ions in pure ionic compounds have an organized three dimensional arrangement (a crystal) described using empirical formulas of formula unit

•The charges on the ions must balance•CaCl2: 1 calcium ion with +2 charge and 2 chloride ions with a -1 charge

•Al2(SO4)3: 2 aluminum ions with a +3 charge and 3 sulfate ions with -2 charge

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Naming Ionic Compounds

E.g.:NaCl : Sodium ChlorideNaNO2: Sodium Nitrite

E.g.:CuO: Copper (II) oxide or…Cu2O: Copper (I) oxide or…

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Naming Acids

• Acids are molecules that contain dissociable hydrogen atom (e.g., HCl, HBr, and HCN)• Acids are named by adding the prefix hydro- to the name of the compound and then replacing the suffix -ide with –ic

• Hydrogen chloride (HCl) Hydrochloric acid• Hydrogen bromide (HBr) Hydrobromic acid• Hydrogen cyanide (HCN) Hydrocyanic acid

• Many of the oxygen-rich polyatomic negative ions form acids that are named by replacing the suffix -ate with -ic and the suffix -ite with -ous

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Acids containing ions ending with -ide often become hydro -ic acid F- (fluoride) => HF hydrofluoric acid S2- (sulfide) => H2S hydrosulfuric acid

Acids containing ions ending with -ate usually become -ic acid CH3CO2

- (acetate) => CH3CO2H acetic acid

CO32- (carbonate) => H2CO3 carbonic acid

BO33- (borate) => H3BO3 boric acid

NO3- (nitrate) => HNO3 nitric acid

SO42- (sulfate) => H2SO4 sulfuric acid

ClO4- (perchlorate) => HClO4 perchloric acid

PO43- (phosphate) => H3PO4 phosphoric acid

MnO4- (permanganate) => HMnO4 permanganic acid

CrO42- (chromate)=> H2CrO4 chromic acid

ClO3- (chlorate) => HClO3 chloric acid

Acids containing ions ending with -ite usually become -ous acid ClO2

- (chlorite) => HClO2 chlorous acid

NO2- (nitrite) => HNO2 nitrous acid

SO32- (sulfite) => H2SO3 sulfurous acid

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The Mole

Relates the atomic mass to a unit of gram for lab purposes

The number of carbon atoms in exactly 12 grams of pure 12C

Modern techniques have been used to define this number as 6.02214199 x 1023

This is called Avogadro’s number (NA) 1 gram = 6.022 1023 amu

Molar mass = Mass (in grams) of 1 mole = atomic mass (amu) x 6.022 1023 x 1g/ 6.022 1023 amu

Numerically equivalent to atomic mass

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Molar masses of some substances

Element Number of Atoms Mass of Sample (g)

AluminiumGoldIronSulfurBoronXenon

6.02214199 x 1023

6.02214199 x 1023

6.02214199 x 1023

6.02214199 x 1023

6.02214199 x 1023

6.02214199 x 1023

26.98196.9755.8532.0710.81131.30

Just like 1 dozen eggs is 12 eggs

1 mole of Copper is 63.5 grams and 6.022 x 1023 atoms

Comparison of 1 mole samples of various elements

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Molar Mass of Compounds

A substance’s molar mass (or molecular weight) is the mass in grams of one mole of the compound

Molar mass of CO2? CO2 = 44.01 grams per mole

1 C = 12.012 O: 2 x 16.00 = 32.00

Molar mass of Al2(SO4)3?

2 mol Al x 26.98 g/mol = 53.96 g Al3 mol S x 32.07 g/mol = 96.21 g S

12 mol O x 16.00 g/mol = 192.00 g OMass of 1 mol of Al2(SO4)3= 342.17 g

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C8H17OH HgI2

CH3OH

S8

One mole each of various substances

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ExerciseWhat amount (moles) is represented by each of these samples?a) 20.0 mg caffeine, C8H10N4O2.

b) 2.72 x 1021 molecules of ethanol, C2H5OH.

c) 1.50 g of dry ice, CO2.

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Percent Composition Percent composition:

Percentage by mass contributed by each element in a substance.Shows how many grams of each element exist in 100 g of a compound

mass of element in compoundmass of compound

Mass percent of an element:

Mass% = x 100%

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Percent Composition

For iron in iron (III) oxide, (Fe2O3)

Molar mass of Fe2O3 = 159.69 g

Mass of Fe = 2 mol x 55.85 g/mol = 111.7 g

Mass % Fe = x 100% = 69.95%111.7

159.69

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Sodium Hydrogen Carbonate, commonly called bicarbonate of soda, is used in many commercial products (antacids). It has the chemical formula NaHCO3. What are the mass percents of Na, H, C, and O.

Mass of Na = 1 mol x 22.99 g/mol = 22.99 g NaMass of H = 1 mol x 1.008 g/mol = 1.008 g HMass of C = 1 mol x 12.01 g/mol = 12.01 g CMass of O = 3 mol x 16.00 g/mol = 48.00 g O

84.01 g NaHCO3

Mass % Na: 22.99g/84.01g x 100% = 27.36%Mass % H: 1.008g/84.01g x 100 % = 1.200%Mass % C: 12.01g/84.01g x 100% = 14.30%Mass % O: 48.00g/84.01g x 100% = 57.14%

27.36% + 1.200% + 14.30% + 57.14% = 100%

Percent Composition