Atoms and Molecules: An Introduction to Chemistry, Slides of Chemistry

Download Atoms and Molecules: An Introduction to Chemistry and more Slides Chemistry in PDF only on Docsity!

“Bohr”ing you with atoms  The study ofchemistry begins withthe basic unit ofmatter, the atom.  What is matter?  Anything that hasmass and takes upspace.

The subatomic particles that make

up atoms are

^ Protons (+) are

positive located in the center ofatom  Neutrons (=)

neutral located in the center ofthe atom  Electrons (-)

negative and are located in spacearound the nucleus. Theyare 1/1840 the size of aproton.

^ Because protons andelectrons have equal andopposite charges, atomsare neutral.

Isotopes

^ Are atoms of thesame element with adifferent number ofneutrons.

^ All 3 isotopes havethe same chemicalproperties, becausethey all have thesame number ofelectrons.

Nonradioactive carbon-12 Nonradioactive carbon-13^ 6 electrons6 protons6 neutrons

Radioactive carbon- 6 electrons6 protons7 neutrons

6 electrons6 protons8 neutrons

How radioactive isotopes work  When an organism isalive it constantlyabsorbing (C-14).  However when anorganism dies the C-14 begins to breakdown, ½ the quantityof death every 5,730years.  Web site (ingest)

Other Radioactive Isotopes  Can be used  To treat cancer  Kill bacteria  As “tracers”

Chemical Compounds

^ Are formed whenmolecules of two ormore atoms arejoined together. ^ The chemicalproperties of acompound are verydifferent from theelements it is madeup of.

Sodium and Chloride

^ Are very differentelements. ^ Chlorine (Cl) is apoisonous green gasthat was used to killsoldiers in WWI. ^ Sodium (Na) – is asilvery metal.

Chemical Bonds

^ Atoms in compoundsare held together bychemical bonds. ^ Bond formationinvolves the electronsthat surround eachnucleus known asvalance electrons.

Ionic Bonds: One big greedy thief

dog

^ Ionic bonding can be bestimagined as one biggreedy dog steeling theother dog’s bone. ^ The bones represent theelectrons up for grabs. ^ When the big dog gainsan electron he becomesnegative, and when thelittle dog looses anelectron he becomespositive. ^ The two ions areattracted very strongly toeach other as a result ofthe opposite charges.

Covalent Bonds

^ Covalent bond isformed when^ electrons are sharedbetween atoms. ^ Very strong bond.

Molecules

^ When atoms arejoined together by a^ covalent bond

, they form molecules.  The molecule is thesmallest unit of mostcompounds.

Van der Waals forces

^ Some atoms have astronger attraction foreelectrons than do otheratoms. There for, whenatoms in a covalent bondshare electrons their notalways equal. ^ A slight attraction candevelop between theoppositely chargedregions of nearbymolecules. ^ The results are everchanging “hot spots” ofpositive and negativecharge that enable allatoms to stick together.

Polar Covalent Bonds

^ A type of covalentbond that differs inelectronegativity. ^ The electrons arepulled closer to thelarger atom, making itslightly negative andthe other slightlypositive ^ An example of a polarmolecule is water.

Hydrogen Bonding

^ Water is a polarmolecule. ^ Water has a partialpositive an negativecharge. The (O) is (-)and the hydrogen’sare (+). ^ Hydrogen bonds areweak. ^ Shock wave demo