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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
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Polar and Non-Polar
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+ +--
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