Matter and Atomic Matter and Atomic StructureStructure

Text ref. Ch.3, (pg. 52)Text ref. Ch.3, (pg. 52)

ContentsContents

What are elements?What are elements?

How atoms combineHow atoms combine

3.1: What Are Elements?3.1: What Are Elements?

Text ref. 52-59 Text ref. 52-59

ObjectivesObjectives

Describe the particles within atoms and Describe the particles within atoms and the structure of atoms.the structure of atoms.

Relate the energy levels of atoms to the Relate the energy levels of atoms to the chemical properties of elements.chemical properties of elements.

Define the concept of isotopes.Define the concept of isotopes.

ElementsElements

Defined as a substance that cannot be Defined as a substance that cannot be broken down into simpler substances by broken down into simpler substances by physical or chemical means.physical or chemical means.

92 naturally occurring elements 92 naturally occurring elements

Elements are organized using the Periodic Elements are organized using the Periodic Table of ElementsTable of Elements

H1

Hydrogen

1.008

Element name

Atomic number

Element symbol

Average atomic number

Text ref. 917, appendix G

Elements and the AtomElements and the Atom

Smallest particle of an element that retains the Smallest particle of an element that retains the properties and characteristics of that element.properties and characteristics of that element.

Composed of subatomic particlesComposed of subatomic particles Nucleus: center or atom, composed of protons and Nucleus: center or atom, composed of protons and

neutronsneutrons Proton: tiny particle having a positive chargeProton: tiny particle having a positive charge Neutron: particle having no charge, but about the Neutron: particle having no charge, but about the

same masssame mass Electron: much smaller mass than proton or neutron, Electron: much smaller mass than proton or neutron,

but has a negative charge equal to a protonbut has a negative charge equal to a proton

Electrons in Energy LevelsElectrons in Energy Levels

Electrons occupy regions of space around the Electrons occupy regions of space around the nucleus of an atom known as energy levels.nucleus of an atom known as energy levels.

Each energy level contains a number of orbitals.Each energy level contains a number of orbitals.

The number of electrons that may be found at an The number of electrons that may be found at an energy level can be detemined by the following energy level can be detemined by the following formula.formula.

#electrons = 2n#electrons = 2n22

The electrons in the outermost energy The electrons in the outermost energy level of an atom determine in chemical level of an atom determine in chemical properties. These outermost electrons are properties. These outermost electrons are known as known as valence electronsvalence electrons..

Isotopes and IonsIsotopes and Ions

The identity of an atom (what element it is) The identity of an atom (what element it is) is determined the # of protons in its is determined the # of protons in its nucleus.nucleus.

An An ionion is an atom of an element which has is an atom of an element which has gained or lost electrons.gained or lost electrons.

An An isotopeisotope is an atom of an element which is an atom of an element which has greater or fewer neutrons.has greater or fewer neutrons.

H2

1

Mass number

Atomic number

RadioactivityRadioactivity

Nuclear decay as particles are lost in an Nuclear decay as particles are lost in an atom leads to the emission of radiation. atom leads to the emission of radiation. Types of radiation include…Types of radiation include… Alpha: helium nucleusAlpha: helium nucleus Beta: electronBeta: electron Gamma: high energy EM radiationGamma: high energy EM radiation

Elemental AbundancesElemental Abundances

Elements are not Elements are not found in equal found in equal numbers in the numbers in the universe or on Earth. universe or on Earth. Some are more Some are more common than others.common than others.

ElementElement Parts per millionParts per million

HydrogenHydrogen 739,000739,000

HeliumHelium 240,000240,000

OxygenOxygen 10,70010,700

CarbonCarbon 4,6004,600

NeonNeon 1,3401,340

IronIron 1,0901,090

NitrogenNitrogen 950950

SiliconSilicon 650650

MagnesiumMagnesium 580580

SulfurSulfur 440440

All OthersAll Others 650650

Abundance of Elements in the Universe

Elemental composition of Earth's ocean water (by mass)

ElementElement PercentPercent ElementElement PercentPercent

OxygenOxygen 85.8485.84 SulfurSulfur 0.0910.091

HydrogenHydrogen 10.8210.82 CalciumCalcium 0.040.04

ChlorineChlorine 1.941.94 PotassiumPotassium 0.040.04

SodiumSodium 1.081.08 BromineBromine 0.00670.0067

MagnesiumMagnesium 0.12920.1292 CarbonCarbon 0.00280.0028

ElementElement Percent Percent by massby mass

OxygenOxygen 6565

CarbonCarbon 1818

HydrogenHydrogen 1010

NitrogenNitrogen 33

CalciumCalcium 1.51.5

PhosphorusPhosphorus 1.21.2

PotassiumPotassium 0.20.2

SulfurSulfur 0.20.2

ChlorineChlorine 0.20.2

SodiumSodium 0.10.1

MagnesiumMagnesium 0.050.05

IronIron, , CobaltCobalt, , CopperCopper, , ZincZinc, , IodineIodine

<0.05 <0.05 eacheach

Selenium, Selenium, FluorineFluorine

<0.01 <0.01 eacheach

Human Body

CompoundsCompounds

Substance composed of atoms of two or Substance composed of atoms of two or more different elements that are more different elements that are chemically combined.chemically combined. Ex. water (HEx. water (H22O)O)

baking soda (NaHCObaking soda (NaHCO33))

Emerald (BeEmerald (Be33AlAl22(SiO(SiO33))66) )

Why do atoms form chemical Why do atoms form chemical bonds?bonds?

To achieve stability.To achieve stability.

Electron configuration is the keyElectron configuration is the key

Full set of electrons in valence shell is Full set of electrons in valence shell is most stable arrangement.most stable arrangement.

Covalent bondingCovalent bonding

Bond formed when electrons are shared Bond formed when electrons are shared by atoms.by atoms. Ex. COEx. CO22

Usually forms between two nonmetalsUsually forms between two nonmetals

MoleculesMolecules

Composed of two or more atoms held Composed of two or more atoms held together by covalent bonds.together by covalent bonds. Have no overall electrical charge Have no overall electrical charge

Protons equal electronsProtons equal electrons

Polar MoleculesPolar Molecules

Unequal sharing of electrons results in Unequal sharing of electrons results in polar molecules.polar molecules.

Positive charge

Negative charge

IonsIons

Atom that has gained or lost electrons.Atom that has gained or lost electrons.

Loss or gain of electrons determined by Loss or gain of electrons determined by electron stability.electron stability.

Atoms gain or lose electrons as necssary, Atoms gain or lose electrons as necssary, in order to have a complete (full) valence in order to have a complete (full) valence electron shellelectron shell

Ionic BondingIonic Bonding

Bonding that occurs when electrons are Bonding that occurs when electrons are donated from one ion to another. donated from one ion to another.

Positive ions are always written first in Positive ions are always written first in chemical formula.chemical formula. Ex: NaCl where NaEx: NaCl where Na+ + and Cland Cl--

Ionic BondingIonic Bonding

The ratio of positive to negative ions in an The ratio of positive to negative ions in an ionic bond depends on the charge of each ionic bond depends on the charge of each ion.ion. MgMg+2+2 Cl Cl-1 -1 = MgCl= MgCl2 2 = Magnesium chloride= Magnesium chloride CaCa+2+2 S S-2-2 = CaS = Calcium sulfide = CaS = Calcium sulfide NaNa+1 +1 SOSO44

-2-2 = Na = Na22SOSO44 = Sodium sulfate = Sodium sulfate

Metallic BondsMetallic Bonds

Bonding that occurs between atoms of a Bonding that occurs between atoms of a metal.metal.

Accounts for the properties of metalsAccounts for the properties of metals Malleability: ability to be hammered into Malleability: ability to be hammered into

sheets or shapedsheets or shaped Ductility: ability to be pulled or stretched into Ductility: ability to be pulled or stretched into

wirewire Conductivity: ability to conduct electrical Conductivity: ability to conduct electrical

current and transfer thermal energycurrent and transfer thermal energy

Metallic bonding is characteristic of delocalized electrons

Chemical ReactionsChemical Reactions

Process where substances are changed Process where substances are changed by chemical meansby chemical means

Represented by chemical equations.Represented by chemical equations. Identify the reactants and products in a Identify the reactants and products in a

reactionreaction Identify relative numbers of each reactant and Identify relative numbers of each reactant and

product in the reactionproduct in the reaction Ex. 2HEx. 2H22 + O + O22 → 2H→ 2H22OO

2H2H22 + O + O22 → → 2H2H22OO

Coefficient: identifies the # of molecules needed for the reaction

reactantsproduct

Mixtures and SolutionsMixtures and Solutions

Mixtures are Mixtures are combinations of combinations of substances that can be substances that can be separated physically, separated physically, whereas chemical whereas chemical compounds cannot be compounds cannot be separated without separated without chemical processes.chemical processes.

Types of MixturesTypes of Mixtures

Homogeneous: mixture Homogeneous: mixture which is uniform (the which is uniform (the same) throughout.same) throughout.

Ex. SolutionsEx. Solutions

Heterogeneous: mixture Heterogeneous: mixture which is not uniform which is not uniform throughout (i.e. separate throughout (i.e. separate layers)layers)

Acids and BasesAcids and Bases

An acid is a solution containing a An acid is a solution containing a substance the produces Hydrogen ions substance the produces Hydrogen ions (H(H++) in water.) in water. Ex. = HCl, or hydrochloric acidEx. = HCl, or hydrochloric acid

HCl = HHCl = H++ + Cl + Cl--

Acids and BasesAcids and Bases

A base is a solution containing a A base is a solution containing a substance that produces hydroxide ions substance that produces hydroxide ions (OH(OH--) in water.) in water. Ex. NaOH, or sodium hydroxideEx. NaOH, or sodium hydroxide

NaOH = NaNaOH = Na++ + OH + OH--

pH scalepH scale

Measures the strength of acids and bases Measures the strength of acids and bases relative to each other.relative to each other.

pH identifies the % Hydrogen ions in a pH identifies the % Hydrogen ions in a solution.solution.

Acids and bases can be combined to Acids and bases can be combined to neutralize each other.neutralize each other.