““Bohr”ing you with atomsBohr”ing you with atoms

The study of The study of chemistry begins with chemistry begins with the basic unit of the basic unit of matter, the atommatter, the atom..

What is matter?What is matter? Anything that has Anything that has

mass and takes up mass and takes up space.space.

The subatomic particles that make The subatomic particles that make up atoms are up atoms are

Protons (+) are Protons (+) are positivepositive located in thelocated in the center center of of atomatom

Neutrons (=) Neutrons (=) neutralneutral located in the located in the centercenter of of the atomthe atom

Electrons (-) Electrons (-) negativenegative and are located and are located in space in space around the nucleus.around the nucleus. They They are 1/1840 the size of a are 1/1840 the size of a proton.proton.

Because protons and Because protons and electrons have equal and electrons have equal and opposite charges, atoms opposite charges, atoms are neutral.are neutral.

Elements and IsotopesElements and Isotopes

Element is one type Element is one type of atom.of atom.

Their are over 100 Their are over 100 elements in elements in existence, but only a existence, but only a few are fond in living few are fond in living organisms.organisms.

Atom BuilderAtom Builder

C6

12.011Carbon

IsotopesIsotopes Are atoms of the Are atoms of the

same element with a same element with a different number of different number of neutrons.neutrons.

All 3 isotopes have All 3 isotopes have the same chemical the same chemical properties, because properties, because they all have the they all have the same number of same number of electrons.electrons.

6 electrons6 protons6 neutrons

Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14

6 electrons6 protons7 neutrons

6 electrons6 protons8 neutrons

How radioactive isotopes workHow radioactive isotopes work

When an organism is When an organism is alive it constantly alive it constantly absorbing (C-14).absorbing (C-14).

However when an However when an organism dies the C-organism dies the C-14 begins to break 14 begins to break down, ½ the quantity down, ½ the quantity of death every 5,730 of death every 5,730 years. years.

Web site (ingest) Web site (ingest)

Radio Active IsotopesRadio Active Isotopes

Have unstable nuclei Have unstable nuclei and break down at a and break down at a constant rate over constant rate over time.time.

Geologist use Geologist use radioactive isotopes radioactive isotopes to determine the age to determine the age of a fossil. of a fossil. (C-14)(C-14)

Other Radioactive IsotopesOther Radioactive Isotopes

Can be used Can be used To treat cancerTo treat cancer Kill bacteriaKill bacteria As “tracers”As “tracers”

Chemical CompoundsChemical Compounds

Are formed when Are formed when molecules of two or molecules of two or more atoms are more atoms are joined together.joined together.

The chemical The chemical properties of a properties of a compound are very compound are very different from the different from the elements it is made elements it is made up of.up of.

Two Types of CompoundsTwo Types of Compounds

Inorganic compoundsInorganic compounds Lack CarbonLack Carbon Non livingNon living For example water is For example water is

made up of 2 made up of 2 hydrogen’s and 1 hydrogen’s and 1 oxygen. oxygen.

Organic compoundsOrganic compounds Contain CarbonContain Carbon Must come from other Must come from other

living thingsliving things..

Sodium and ChlorideSodium and Chloride

Are very different Are very different elements.elements.

Chlorine (Cl) is a Chlorine (Cl) is a poisonous green gas poisonous green gas that was used to kill that was used to kill soldiers in WWI.soldiers in WWI.

Sodium (Na) – is a Sodium (Na) – is a silvery metal. silvery metal.

Chemical BondsChemical Bonds

Atoms in compounds Atoms in compounds are held together by are held together by chemical bonds.chemical bonds.

Bond formation Bond formation involves the electrons involves the electrons that surround each that surround each nucleus known as nucleus known as valance electrons.valance electrons.

Ionic BondsIonic Bonds An Ionic bond is formed An Ionic bond is formed

when one or more when one or more electrons are electrons are transferredtransferred from one from one atom to the other.atom to the other.

An atom that loses an An atom that loses an electron has a (+) charge.electron has a (+) charge.

An atom that gains an An atom that gains an electron has a (-) charge.electron has a (-) charge.

Positively or negatively Positively or negatively charged atoms are known charged atoms are known as as ions.ions.

Ionic bonds are Ionic bonds are not very not very strong. strong.

Ionic Bonds: One big greedy thief Ionic Bonds: One big greedy thief dogdog Ionic bonding can be best Ionic bonding can be best

imagined as one big imagined as one big greedy dog steeling the greedy dog steeling the other dog’s bone.other dog’s bone.

The bones represent the The bones represent the electrons up for grabs.electrons up for grabs.

When the big dog gains When the big dog gains an electron he becomes an electron he becomes negative, and when the negative, and when the little dog looses an little dog looses an electron he becomes electron he becomes positive.positive.

The two ions are The two ions are attracted very strongly to attracted very strongly to each other as a result of each other as a result of the opposite charges.the opposite charges.

Covalent BondsCovalent Bonds

Covalent bond is Covalent bond is formed when formed when electrons are shared electrons are shared between atoms. between atoms.

Very strong bond.Very strong bond.

Covalent Bond: Dogs of equal Covalent Bond: Dogs of equal strengthstrength

Covalent bonds can Covalent bonds can be thought as two or be thought as two or more dogs with equal more dogs with equal attraction to the attraction to the bones. Since the bones. Since the dogs (atoms) are dogs (atoms) are identical, then the identical, then the dogs share the pairs dogs share the pairs of available bones of available bones evenly.evenly.

MoleculesMolecules

When atoms are When atoms are joined together by a joined together by a covalent bondcovalent bond, they , they form molecules.form molecules.

The molecule is the The molecule is the smallest unit of most smallest unit of most compounds.compounds.

Van der Waals forcesVan der Waals forces Some atoms have a Some atoms have a

stronger attraction fore stronger attraction fore electrons than do other electrons than do other atoms. There for, when atoms. There for, when atoms in a covalent bond atoms in a covalent bond share electrons their not share electrons their not always equal. always equal.

A slight attraction can A slight attraction can develop between the develop between the oppositely charged oppositely charged regions of nearby regions of nearby molecules.molecules.

The results are ever The results are ever changing “hot spots” of changing “hot spots” of positive and negative positive and negative charge that enable all charge that enable all atoms to stick togetheratoms to stick together. .

Van der Waals forces in ActionVan der Waals forces in Action A geckos foot is covered by as A geckos foot is covered by as

many as a ½ a million tiny hair many as a ½ a million tiny hair like projections. like projections.

Each projection is divided into Each projection is divided into hundreds of tiny flat –surfaced hundreds of tiny flat –surfaced fibers.fibers.

This design allows the gecko’s This design allows the gecko’s foot to come in contact with an foot to come in contact with an extremely large area of the wall extremely large area of the wall at the molecular level allowing at the molecular level allowing Van’s forces to occur.Van’s forces to occur.

The combined strength of all The combined strength of all the Van der Waals froces allows the Van der Waals froces allows the gecko to walk up walls.the gecko to walk up walls.

Polar Covalent BondsPolar Covalent Bonds

A type of covalent A type of covalent bond that differs in bond that differs in electronegativityelectronegativity..

The electrons are The electrons are pulled closer to the pulled closer to the larger atom, making it larger atom, making it slightly negative and slightly negative and the other slightly the other slightly positivepositive

An example of a polar An example of a polar molecule is water.molecule is water.

Hydrogen BondingHydrogen Bonding

Water is a polar Water is a polar molecule.molecule.

Water has a partial Water has a partial positive an negative positive an negative charge. The (O) is (-) charge. The (O) is (-) and the hydrogen’s and the hydrogen’s are (+). are (+).

Hydrogen bonds are Hydrogen bonds are weak.weak.

Shock wave demoShock wave demo

Match the BondsMatch the Bonds

Water has strong cohesion and Water has strong cohesion and high surface tensionhigh surface tension

Cohesion- is the Cohesion- is the attraction between attraction between molecules of the same molecules of the same substance.substance.

A single water molecule A single water molecule may be involved in as may be involved in as many as 4 hydrogen many as 4 hydrogen bonds at the same time.bonds at the same time.

Cohesion explains why Cohesion explains why some insects can walk on some insects can walk on water.water.

Water adheres to other moleculesWater adheres to other molecules

Adhesion is an attraction Adhesion is an attraction between molecules of between molecules of different substancesdifferent substances..

The surface water in a The surface water in a graduate cylinder dips graduate cylinder dips slightly in the center slightly in the center because the adhesion because the adhesion between water molecules between water molecules and glass is stronger than and glass is stronger than the cohesion between the cohesion between water molecule.water molecule.

Ice FloatsIce Floats

Unlike most Unlike most substances when substances when water freezes it water freezes it expands, and expands, and becomes less dense.becomes less dense.

What effects would What effects would that have on life?that have on life?

Water is an excellent solventWater is an excellent solvent

Water is a solvent –Water is a solvent – the the substance in which the substance in which the solute is dissolved.solute is dissolved.

In a salt-water solution, In a salt-water solution, table salt is the solute.table salt is the solute.

Water is the solvent of Water is the solvent of life.life.

Dissolve demoDissolve demo

Water has a high heat capacityWater has a high heat capacity

Water changes Water changes temperature very temperature very slowly.slowly.

Thus the temperature Thus the temperature of large bodies of of large bodies of water are very stable. water are very stable.

Evaporative CoolingEvaporative Cooling

As water evaporates, As water evaporates, the surface of the the surface of the water that remains water that remains behind cools down.behind cools down.

Why do we sweat Why do we sweat more on a humid more on a humid day?day?

Mr. WalcottMr. Walcottbefore a job before a job

interviewinterview

What gives water its special What gives water its special propertiesproperties

Individual water Individual water molecules are polar and molecules are polar and they stick together by they stick together by means of hydrogen means of hydrogen bonds.bonds.

Hydrogen bonds are Hydrogen bonds are weak and only last a weak and only last a fraction of a second.fraction of a second.

It takes a lot of energy to It takes a lot of energy to overcome the combined overcome the combined attraction of many attraction of many hydrogen bonds.hydrogen bonds.

This explainsThis explains Waters great capacity to Waters great capacity to

store heatstore heat High boiling pointHigh boiling point Surface tensionSurface tension

Acid, Bases, and pHAcid, Bases, and pH

Hydrogen Ion (H+)Hydrogen Ion (H+) Hydroxide Ion (OH-)Hydroxide Ion (OH-)

WaterWater

Acids (H+)Acids (H+)

An acids from H+ ions in solutionsAn acids from H+ ions in solutions have more H+ ions than pure waterhave more H+ ions than pure water pH values below 7pH values below 7

Bases (OH-)Bases (OH-)

Produce hydroxide ions (OH-)Produce hydroxide ions (OH-) Have lower amounts of H+ ions then pure Have lower amounts of H+ ions then pure

water.water. pH values above 7pH values above 7

BuffersBuffers

Weak acids or bases Weak acids or bases that can react with that can react with strong acids or bases strong acids or bases to prevent sudden to prevent sudden changes in pH.changes in pH.

The human body has The human body has a buffer system.a buffer system.

The most common The most common buffer is the buffer is the bicarbonate ion.bicarbonate ion.

The pH scaleThe pH scale

The pH scale tells us how The pH scale tells us how many H+ ions there are in many H+ ions there are in a solution.a solution.

The higher the pH the The higher the pH the more basic the solutionmore basic the solution

The lower the pH the The lower the pH the more acidic a solution is.more acidic a solution is.

pH of 7 is neutralpH of 7 is neutral pH scale animationpH scale animation

What to do when you get stungWhat to do when you get stung

When a wasp stings it When a wasp stings it injects an alkali injects an alkali (base) into the victim(base) into the victim

You can neutralize You can neutralize the sting with vinegar the sting with vinegar (an acid)(an acid)

TumsTums

Are a baseAre a base Neutralize the Neutralize the

stomachs acids.stomachs acids.