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AP – Chemistry Review!. Atoms. Building blocks of all matter Atoms of same element share same chemical properties Made of subatomic particles. Subatomic Particles. Atoms contain three smaller particles: Protons (+1 charge) – inside nucleus Neutrons (no charge) – inside nucleus
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Atoms • Building blocks of all matter • Atoms of same element share same chemical properties • Made of subatomic particles
Subatomic Particles • Atoms contain three smaller particles: • Protons (+1 charge) – inside nucleus • Neutrons (no charge) – inside nucleus • Electrons (-1 charge) – outside nucleus • Valence Electrons – outer most electrons (used in bonding) Atomic # = # of protons C 6 Atomic mass = protons plus neutrons 12
Elements • Are made of only one type of atom • Most common elements we will use: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorous (P), Sulfur (S), Calcium (Ca), Potassium (K), Sodium (Na), Chlorine (Cl), Magnesium (Mg)
Trace Elements • Required by an organism in extremely minute quantities • Indispensable for life • B, Cr, Co, Cu, F, I, Fe, Mg, Mo, Se, Si, Sn, V, Zn
Isotopes • An element that has the same atomic number but different mass number • Same # of protons, different # neutrons • C-12, C-13 and C-14 • U-238 and U-240 • Radioactive isotopes can be used to date fossils
Isotopes of Carbon # of electrons, protons stay same!!! Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14 6 electrons 6 protons 6 neutrons 6 electrons 6 protons 8 neutrons 6 electrons 6 protons 7 neutrons
Electron Configuration • Distribution of electrons in an atom’s electron shells • Determines chemical behavior • Determined also by # of valence electrons • Remember: Octet Rule…
Compounds • Pure substance composed of 2 or more elements in a fixed ratio • i.e. NaCl, H2O • Have unique properties when atoms (with incomplete valence shells) combine
Ionic Bonding • Forms when atoms gain or lose electrons • Between M and NM • Creates an ion – an atom thathas a charge (ex: Ca+2, Cl -1) • Strong bonds in crystals (solid) , weak bonds in water (crystals readily dissociate in water) • Called “salts” • i.e. NaCl, CaCl2 • Loss of electron = (+) charge = Cation • Gain of electron = (-) charge = Anion
Covalent Bonding • Forms when atoms share electrons • Between NM and NM • 1 bond = 2 electrons are shared = Line • i.e. H2O, C6H12O6, NH4+, CH4 • Two types: Polar and Non-Polar
Non-Polar Covalent • A covalent bond in which electrons areshared equally • Electronegativity of atoms is about the same • Usually made of one type of atom • O2, H2, N2, Cl2
Polar Covalent • A covalent bond in which electrons are not shared equally • Electronegativities of atoms are different • Slightly oppositely charged ends attract other charged molecules • H2O – the Hydrogen end is (+) and the Oxygen end is (-)
Other Attractions • Hydrogen Attraction – between Hydrogen and another molecule – weaker than a covalent or ionic bond.
Function and Shape • A molecule has a characteristic size and shape • Function of many molecules depends upon their shape
Chemical Reactions • Making and breaking chemical bonds • Leads to changes in the composition of matter • Reactants undergo changes into products • Matter is conserved, so atoms are only rearranged to form products