Basic ChemistryBasic Chemistry

Matter and EnergyMatter and Energy

Matter—anything that occupies Matter—anything that occupies space and has mass (weight)space and has mass (weight)

Energy—the ability to do workEnergy—the ability to do work– ChemicalChemical– ElectricalElectrical– MechanicalMechanical– RadiantRadiant

Composition of MatterComposition of Matter

Elements—fundamental units of Elements—fundamental units of mattermatter– 96% of the body is made from four 96% of the body is made from four

elementselements Carbon (C)Carbon (C) Oxygen (O)Oxygen (O) Hydrogen (H)Hydrogen (H) Nitrogen (N)Nitrogen (N)

Atoms—building blocks of elementsAtoms—building blocks of elements

Atomic StructureAtomic Structure

NucleusNucleus– Protons (pProtons (p++))– Neutrons (nNeutrons (n00))

Outside of Outside of nucleusnucleus– Electrons (eElectrons (e--))

Figure 2.1

Atomic Structure of Atomic Structure of Smallest AtomsSmallest Atoms

Identifying ElementsIdentifying Elements

Atomic number—equal to the Atomic number—equal to the number of protons that the atom number of protons that the atom containscontains

Atomic mass number—sum of the Atomic mass number—sum of the protons and neutronsprotons and neutrons

Isotopes and Atomic WeightIsotopes and Atomic Weight

IsotopesIsotopes– Have the same number of protonsHave the same number of protons– Vary in number of neutronsVary in number of neutrons

Figure 2.3

Isotopes and Atomic WeightIsotopes and Atomic Weight

Atomic weightAtomic weight– Close to mass number of most abundant Close to mass number of most abundant

isotopeisotope– Atomic weight reflects natural isotope Atomic weight reflects natural isotope

variationvariation

RadioactivityRadioactivity

RadioisotopeRadioisotope– Heavy isotopeHeavy isotope– Tends to be unstableTends to be unstable– Decomposes to more stable isotopeDecomposes to more stable isotope

Radioactivity—process of Radioactivity—process of spontaneous atomic decayspontaneous atomic decay

Molecules and CompoundsMolecules and Compounds

Molecule—two or more Molecule—two or more likelike atoms atoms combined chemicallycombined chemically

Compound—two or more Compound—two or more differentdifferent atoms combined chemicallyatoms combined chemically

Chemical ReactionsChemical Reactions

Atoms are united by chemical bondsAtoms are united by chemical bonds Atoms dissociate from other atoms Atoms dissociate from other atoms

when chemical bonds are brokenwhen chemical bonds are broken

Electrons and BondingElectrons and Bonding

Electrons occupy energy levels called Electrons occupy energy levels called electron shellselectron shells

Electrons closest to the nucleus are Electrons closest to the nucleus are most strongly attractedmost strongly attracted

Each shell has distinct propertiesEach shell has distinct properties– The number of electrons has an upper The number of electrons has an upper

limitlimit– Shells closest to the nucleus fill firstShells closest to the nucleus fill first

Electrons and BondingElectrons and Bonding

Bonding involves interactions Bonding involves interactions between electrons in the outer shell between electrons in the outer shell (valence shell)(valence shell)

Full valence shells do not form bondsFull valence shells do not form bonds

Inert ElementsInert Elements

Atoms are stable (inert) when the Atoms are stable (inert) when the outermost shell is completeoutermost shell is complete

How to fill the atom’s shellsHow to fill the atom’s shells– Shell 1 can hold a maximum of 2 Shell 1 can hold a maximum of 2

electronselectrons– Shell 2 can hold a maximum of 8 Shell 2 can hold a maximum of 8

electronselectrons– Shell 3 can hold a maximum of 18 Shell 3 can hold a maximum of 18

electronselectrons

Inert ElementsInert Elements

Atoms will gain, lose, or share Atoms will gain, lose, or share electrons to complete their outermost electrons to complete their outermost orbitals and reach a stable stateorbitals and reach a stable state

Rule of eightsRule of eights– Atoms are considered stable when their Atoms are considered stable when their

outermost orbital has 8 electronsoutermost orbital has 8 electrons– The exception to this The exception to this rule of eightsrule of eights is is

Shell 1, which can only hold 2 electronsShell 1, which can only hold 2 electrons

Inert ElementsInert Elements

Figure 2.5a

Reactive ElementsReactive Elements Valence shells are not full and are Valence shells are not full and are

unstableunstable Tend to gain, lose, or share electronsTend to gain, lose, or share electrons

– Allow for bond formation, which Allow for bond formation, which produces stable valenceproduces stable valence

Chemical BondsChemical Bonds

Ionic bondsIonic bonds– Form when electrons are completely Form when electrons are completely

transferred from one atom to anothertransferred from one atom to another IonsIons

– Charged particlesCharged particles Anions are negativeAnions are negative Cations are positiveCations are positive Either donate or accept electronsEither donate or accept electrons

Ionic BondsIonic Bonds

Figure 2.6

+ –

Sodium atom (Na)(11p+; 12n0; 11e–)

Chlorine atom (Cl)(17p+; 18n0; 17e–)

Sodium ion (Na+) Chloride ion (Cl–)

Sodium chloride (NaCl)

ClNaClNa

Chemical BondsChemical Bonds

Covalent bondsCovalent bonds– Atoms become stable through shared Atoms become stable through shared

electronselectrons– Single covalent bonds share one pair of Single covalent bonds share one pair of

electronselectrons– Double covalent bonds share two pairs Double covalent bonds share two pairs

of electronsof electrons

Examples of Covalent BondsExamples of Covalent Bonds

Figure 2.7a

Examples of Covalent BondsExamples of Covalent Bonds

Figure 2.7b

Examples of Covalent BondsExamples of Covalent Bonds

Figure 2.7c

PolarityPolarity

Covalently Covalently bonded moleculesbonded molecules– Some are non-Some are non-

polarpolar Electrically neutral Electrically neutral

as a moleculeas a molecule

– Some are polarSome are polar Have a positive Have a positive

and negative sideand negative side

Figure 2.8

Chemical BondsChemical Bonds

Hydrogen bondsHydrogen bonds– Weak chemical bondsWeak chemical bonds– Hydrogen is attracted to the negative Hydrogen is attracted to the negative

portion of polar moleculeportion of polar molecule– Provides attraction between moleculesProvides attraction between molecules

Hydrogen BondsHydrogen Bonds

Figure 2.9

Patterns of Chemical Patterns of Chemical ReactionsReactions

Synthesis reaction (A + BSynthesis reaction (A + BAB)AB)– Atoms or molecules combineAtoms or molecules combine– Energy is absorbed for bond formationEnergy is absorbed for bond formation

Decomposition reaction (ABDecomposition reaction (ABA + B)A + B)– Molecule is broken downMolecule is broken down– Chemical energy is releasedChemical energy is released

Synthesis and Synthesis and Decomposition ReactionsDecomposition Reactions

Figure 2.10a

Synthesis and Synthesis and Decomposition ReactionsDecomposition Reactions

Figure 2.10b

Patterns of Chemical Patterns of Chemical ReactionsReactions

Exchange reaction (AB + CExchange reaction (AB + CAC + B)AC + B)– Involves both synthesis and Involves both synthesis and

decomposition reactionsdecomposition reactions– Switch is made between molecule parts Switch is made between molecule parts

and different molecules are madeand different molecules are made

Patterns of Chemical Patterns of Chemical ReactionsReactions

Figure 2.10c