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The Structure of The Structure of MatterMatter

Chapter 2: Chemical Basis of Chapter 2: Chemical Basis of LifeLife

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What is Matter?What is Matter?

MatterMatter is anything that has is anything that has weight and takes up space.weight and takes up space.

– This includes the solids, liquids, and This includes the solids, liquids, and gases in our surroundings, as well as gases in our surroundings, as well as inside our bodies.inside our bodies.

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What is it Made of?What is it Made of?

All matter is composed of All matter is composed of substances called substances called ElementsElements..

– At present, 111 elements are known, At present, 111 elements are known, although naturally occurring matter although naturally occurring matter on Earth includes only 92 of them.on Earth includes only 92 of them.

Although some of these elements exist in Although some of these elements exist in a pure form, they occur more frequently a pure form, they occur more frequently in mixtures of chemical combinations.in mixtures of chemical combinations.

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Elements We NeedElements We Need

Living organisms require about 20 Living organisms require about 20 elements.elements.

– Of these carbon, hydrogen, oxygen, Of these carbon, hydrogen, oxygen, phosphate, nitrogen, sulfur make up phosphate, nitrogen, sulfur make up more than 98% (by weight) of the more than 98% (by weight) of the human body.human body.

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ElementsElements

Elements are composed of tiny Elements are composed of tiny particles called particles called AtomsAtoms, which are , which are the smallest complete units of the smallest complete units of elements.elements.

– All the atoms of an element look All the atoms of an element look nearly identical to one another, but nearly identical to one another, but different from atoms of another different from atoms of another element.element.

Atoms vary in size, weight, and the ways Atoms vary in size, weight, and the ways they interact with each other.they interact with each other.

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How are they How are they different?different?

Oxygen Carbon

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Atomic StructureAtomic Structure

An atom consists of a central An atom consists of a central portion, called the portion, called the NucleusNucleus, and , and one or more one or more ElectronsElectrons that move that move around it.around it.

– The nucleus contains one or more The nucleus contains one or more relatively large particles called relatively large particles called ProtonsProtons..

The nucleus also usually contains one or The nucleus also usually contains one or more more NeutronsNeutrons, which are similar in size , which are similar in size to protons.to protons.

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More on Atomic More on Atomic StructureStructure ElectronsElectrons (extremely tiny) each (extremely tiny) each

carry a single, negative electrical carry a single, negative electrical chargecharge

ProtonsProtons each carry a single, each carry a single, positive electrical charge.positive electrical charge.

NeutronsNeutrons are uncharged and are are uncharged and are electrically neutral.electrically neutral.

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Chemistry Vocab. Chemistry Vocab. ReviewReview

Atomic Atomic NumberNumber: the : the number of number of protons in the protons in the atoms of a atoms of a particular particular element.element.

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Chemistry Vocab. Chemistry Vocab. ReviewReview

Atomic WeightAtomic Weight: : Approximately Approximately the number of the number of protons plus the protons plus the number of number of neutrons in each neutrons in each of an element’s of an element’s atoms.atoms.

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Let’s Bond!Let’s Bond!

When atoms combine with other When atoms combine with other atoms, they either gain electrons, atoms, they either gain electrons, lose electrons, or share electrons.lose electrons, or share electrons.

– The electrons of an atom occupy one The electrons of an atom occupy one or more areas of space called or more areas of space called ShellsShells around the nucleus.around the nucleus.

The outermost shell of an atom The outermost shell of an atom determines its chemical behavior.determines its chemical behavior.

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Stability vs. InstabilityStability vs. Instability

Atoms whose outermost electron shells Atoms whose outermost electron shells are filled, have stable structures and are filled, have stable structures and are chemically inactive (are chemically inactive (inertinert)- )- ExampleExample: Helium: Helium

Atoms whose outermost electron shells Atoms whose outermost electron shells are incompletely filled, tend to gain, are incompletely filled, tend to gain, lose, or share electrons in ways that lose, or share electrons in ways that empty or fill their outer shells.empty or fill their outer shells.

In this way, they achieve stable structures.In this way, they achieve stable structures.

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Types of BondsTypes of Bonds

1.1. Ionic BondsIonic Bonds

2.2. Covalent BondsCovalent Bonds

3.3. Hydrogen BondsHydrogen Bonds

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Ionic BondingIonic Bonding An An Ionic BondIonic Bond is a chemical bond formed is a chemical bond formed

between two (oppositely charged) ions by between two (oppositely charged) ions by

the transferring of the transferring of electronselectrons..

– ExampleExample: Sodium ions (Na: Sodium ions (Na++) and chloride ions ) and chloride ions (Cl(Cl--) uniting in this manner form the compound ) uniting in this manner form the compound sodium chloride (NaCl), or table salt.sodium chloride (NaCl), or table salt.

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Covalent BondingCovalent Bonding

Nature likes filled levels for Nature likes filled levels for stability, why not share?stability, why not share?

– A A Covalent BondCovalent Bond is a is a chemical bond formed by chemical bond formed by electron sharing between electron sharing between atoms.atoms.

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Hydrogen BondingHydrogen Bonding A A Hydrogen BondHydrogen Bond

is a weak electrical is a weak electrical attraction between attraction between a hydrogen atom a hydrogen atom (covalently bound (covalently bound to a nitrogen or to a nitrogen or oxygen atom) and oxygen atom) and another nitrogen another nitrogen or oxygen atom or oxygen atom nearbynearby..

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Hydrogen BondingHydrogen Bonding

Hydrogen bonds Hydrogen bonds only occur with only occur with molecules that molecules that are are polarpolar..

Water is polar Water is polar because the because the oxygen atom & oxygen atom & hydrogen atoms hydrogen atoms share electrons share electrons unevenly.unevenly.

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Molecules & Molecules & CompoundsCompounds

When two or more atoms bond, they form a When two or more atoms bond, they form a new kind of particle called a new kind of particle called a MoleculeMolecule..

– If atoms of the same element combine, If atoms of the same element combine, they produce molecules of that element.they produce molecules of that element.

– Example: HExample: H22, O, O22

When atoms of different elements combine, When atoms of different elements combine, they form molecules called they form molecules called CompoundsCompounds..

– A molecule of a compound always contains A molecule of a compound always contains definite kinds and numbers of atoms.definite kinds and numbers of atoms.

– Example: COExample: CO66, H, H22O, CO, C66HH1212OO66

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Chemical ReactionsChemical Reactions

Chemical rxns form or break bonds Chemical rxns form or break bonds between atoms, ions, or molecules, between atoms, ions, or molecules, generating new chemical generating new chemical combinations.combinations.

1. Synthesis Reactions1. Synthesis Reactions

2. Decomposition Reactions2. Decomposition Reactions

3. Exchange Reactions3. Exchange Reactions

4. Reversible Reactions4. Reversible Reactions

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Synthesis Synthesis ReactionsReactions

When two or more atoms When two or more atoms (reactants) bond to form a more (reactants) bond to form a more complex structure (product).complex structure (product).

A + B A + B AB AB

Requires an input of energy Requires an input of energy (endergonic)(endergonic)

Important in the growth of body Important in the growth of body parts and the repair of worn or parts and the repair of worn or damaged tissues.damaged tissues.

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Decomposition Decomposition ReactionsReactions When the bonds within a reactant When the bonds within a reactant

molecule break so that simpler molecule break so that simpler molecules, atoms, or ions form.molecules, atoms, or ions form.

AB AB A + B A + B

Decomposition occurs when foods Decomposition occurs when foods are digested and energy is released are digested and energy is released (exergonic)(exergonic)

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Exchange ReactionExchange Reaction

Parts of two different types of Parts of two different types of molecules trade positions.molecules trade positions.

AB + CD AB + CD AD + CB AD + CB

An example is when an acid reacts An example is when an acid reacts with a base, producing water and with a base, producing water and a salt.a salt.– HCl + NaOH --> NaCl + HHCl + NaOH --> NaCl + H22OO

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Reversible ReactionsReversible Reactions

Most chemical reactions are Most chemical reactions are reversible.reversible.

– The product (or products) of the The product (or products) of the reaction can change back to the reaction can change back to the reactant (or reactants) that reactant (or reactants) that originally underwent the reaction.originally underwent the reaction.

A + B A + B AB AB

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Understanding Understanding ElectrolytesElectrolytes

Some compounds release ions Some compounds release ions when they dissolve in water or when they dissolve in water or react with water molecules. react with water molecules.

– ExampleExample: NaCl releases sodium ions : NaCl releases sodium ions (Na(Na++) and chloride ions (Cl) and chloride ions (Cl--) when it ) when it dissolves:dissolves:

NaCl NaCl Na Na++ + Cl + Cl--

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Understanding Understanding ElectrolytesElectrolytes

NaCl NaCl Na Na++ + Cl + Cl--

Since the resulting solution Since the resulting solution contains electrically charged contains electrically charged particles (ions), it will conduct an particles (ions), it will conduct an electric current.electric current.

– Substances that release ions in Substances that release ions in water are called water are called ElectrolytesElectrolytes..

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Acids & BasesAcids & Bases

Electrolytes that release hydrogen ions Electrolytes that release hydrogen ions in water (Hin water (H++) are called ) are called AcidsAcids..

– ExampleExample: In water, the compound : In water, the compound hydrochloric acid (HCl) releases hydrogen hydrochloric acid (HCl) releases hydrogen ions (Hions (H++) and chloride ions (Cl) and chloride ions (Cl--))

Electrolytes that release hydroxide Electrolytes that release hydroxide ions in water (OHions in water (OH--) are called ) are called BasesBases..

– ExampleExample: The compound sodium : The compound sodium hydroxide (NaOH) releases hydroxide ions hydroxide (NaOH) releases hydroxide ions (OH(OH--) when placed in water.) when placed in water.

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pH ScalepH Scale A value called A value called pHpH measures hydrogen ion measures hydrogen ion

concentration.concentration.

– The pH scale ranges from 0 to 14.The pH scale ranges from 0 to 14.

A solution that contains equal numbers of A solution that contains equal numbers of hydrogen and hydroxide ions is said to be hydrogen and hydroxide ions is said to be neutral, and has a pH of 7.neutral, and has a pH of 7.

A solution that contains more hydrogen than A solution that contains more hydrogen than hydroxide ions has a pH less than 7hydroxide ions has a pH less than 7

A solution that contains less hydrogen than A solution that contains less hydrogen than hydroxide ions has a pH more than 7hydroxide ions has a pH more than 7

Each whole number on the scale represents a Each whole number on the scale represents a tenfold difference in hydrogen ion tenfold difference in hydrogen ion concentration.concentration.

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Human ImplicationsHuman Implications

The pH of human blood is about The pH of human blood is about 7.4 (range is from 7.35 to 7.45)7.4 (range is from 7.35 to 7.45)

– If this pH value drops below 7.35, If this pH value drops below 7.35, the person is said to have the person is said to have AcidosisAcidosis

– If this pH value rises above 7.45, the If this pH value rises above 7.45, the person is said to have person is said to have AlkalosisAlkalosis

Without medical intervention, a person Without medical intervention, a person usually cannot survive if blood pH drops usually cannot survive if blood pH drops to 6.9 or rises to 7.8 for more than a few to 6.9 or rises to 7.8 for more than a few hours.hours.