Chemistry Review

Atoms

Atom - basic unit of matter smallest unit of an

element Three subatomic particles

make up atoms:1.protons2.neutrons3.electrons

Protons and Neutrons

• about the same mass• protons are positively

charged (+) • neutrons carry no charge

at all (0)• Nucleus: center of the

atom, where strong forces bind protons and neutrons together

Electrons Electron is negatively (–)

charged atommuch smaller mass than protons attracted to the positively charged

nucleus and orbit (spin) around it

atoms are electrically neutral:proton # = electron # (same!)(+) + (-) = neutral +3 + -3 = ???

Carbon atom has 6 p’s and 6 e’s

ElementsElement – pure substance that consists entirely of one type of atom 119 known elements

elements are represented by 1-2 letter symbols:C stands for carbonH for hydrogenNa for sodium

Hg for mercury

ElementsAtomic number - # of protons/electrons in the element’s nucleuscarbon’s atomic number is 6therefore: each atom of

carbon has:6 protons and 6 electrons

Mass number - total number of protons plus neutrons in the nucleuscarbon’s mass number is

12.01 (6 protons + 6 neutrons)

NeutronsHow to figure out neutron number:

mass # - atomic # = neutron #

carbon’s mass # is 12.01 (round, 12)carbon’s atomic # is 612 – 6 = ???Carbon has 6 p’s, 6 e’s, and 6 n’s

Let’s try I (iodine)iodine’s mass # is 126.9 (round, 127)iodine’s atomic # is 53127 – 53 = ???Iodine has 53 p’s, 53 e’s, and 74 n’s

Atoms ReviewProtons Neutrons Electrons

Mass

Charge

Location

Chemical CompoundsCompound - a substance formed by the chemical combination of 2 or more elements

displayed in a chemical formula:H2O = water = 2 atoms hydrogen and 1 atom oxygenNaCl = table salt = 1 atom sodium and 1 atom chlorineC6H12O6 = sugar = 6 atoms carbon, 12 atoms

hydrogen, 6 atoms oxygen

Ionic Bonds atoms can gain of lose electrons to become stable Ionic bond - formed when one or more electrons are

transferred from one atom to anotherogain electron – negative chargeo lose electron – positive charge

o Ions - positively and negatively charged atoms

Covalent Bonds sometimes electrons are shared by atoms instead of being

transferred

Covalent bond – occurs through sharing of valence electrons and does not involve charged atoms

when the atoms share:o two electrons single bondo four electrons double bondo six electrons triple bond

Bonding Review

LecturePLUS Timberlake

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LecturePLUS Timberlake

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LecturePLUS Timberlake

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LecturePLUS Timberlake

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Polar and Non-Polar

LecturePLUS Timberlake18

+ +--

Non-Polar Covalent Bond

+ +--

Ionic Bond

Cation Anion

+ +--

Polar Covalent Bond

More Electronegative

Element

Less Electronegative

Element

The Water Molecule

Water is a polarmolecule.

POLAR: a molecule in which the opposite ends have opposite electric charges

Polar Covalent Bonding

Electrons unequally shared between atoms

Atom that pulls on the e- more strongly slightly negative

Atom that has a weaker pull on the e- slightly positive

Produces an uneven charge across the molecule polar

Non-Polar Covalent Bonding

Electrons equally shared between atoms

Produces no charge across the molecule non-polar

Oils are non-polar

Like Dissolves LikePolar substances dissolve in other polar

substancesIonic Compounds are polarExample: Salt in Water

Non-polar substances dissolve in other non-polar substancesExample: Oil based paint and turpentine

Polar and non-polar won’t mixExample: Oil and Water

Like Dissolves Like

Solvent Polarity Solute

Ethyl acetate Non-polar Iodine

Water Polar Copper (II) sulfate

Chloroform Non-polar Iodine