ch. 4 chemistry notes - oak park · pdf filech. 4 chemistry notes earth chemistry sections 4.1...
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Ch. 4 Chemistry Notes
Earth ChemistrySections 4.1 & 4.2
· anything that has mass and takes up space· distinguishing properties
physical - can be observed without changing the composition (color, hardness, boiling pt.)
chemical - describes how a substance reacts with another substance (oxidation, inertness)
Matter
Elements· all matter is composed of elements
currently 11292 occur naturallyliving organisms require about 20
· cannot be broken down into simpler parts· organized on the periodic table of elements· 8 elements make up more than 98% of Earth's crust
oxygen (O), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), potassium (K), magnesium (Mg)
Atoms
· # protons = # of electrons· atomic number = # protons· atomic mass = # protons + # neutrons
· atoms are the smallest unit of matter· atom = nucleus (core) + electron cloud· nucleus contain protons and neutrons
protons carry a positive charge (+)neutrons carry NO charge (0)
· electrons constantly move around the nucleuselectrons carry a negative charge (-)abbreviation = e-
protons + neutrons
number of protons
Identifying ELements
pull arrows for definitions
Isotopes
· atoms of the same element that have different #s of neutrons· slightly different properties because of slightly greater mass· carbon-14
found in all living thingsused to determine age of
things
Ch. 4 Chemistry Notes
Review Questions1. What is matter?2. Describe the structure of an atom.3. Compare atomic number and mass number.4. The # of electrons is equal to the # of what other subatomic particle?5. What is an isotope?
Compounds· compound = 2 or more elements bonded together· a compound's properties are often different from the properties of the elements that make them up
Energy Levels
· energy levels can only hold a specific # of electrons
1st = 2 electrons2nd = 8 electrons (octet)
· a partially filled energy level is not as stable as a full or empty energy level
atoms gain, lose or share electrons
Chemical Bonding· atoms are more stable when their outermost energy level is full...thus, the need for chemical bonding (attaching/joining)· 2 types
ionic - electrons gained or lostcovalent - electrons shared
Ions & Ionic Bonding· ion = an atom that has gained or lost 1 or more e-
nearly empty outer shell = lose electrons (+ ions)nearly full outer shell = gain electrons (- ions)
· ionic bonds form because of the electrical force between oppositely charged ions
Molecules & Covalent Bonds· molecule = two or more atoms held together by covalent bonds (H2O, CO2)· covalent bonds form when 2 atoms share 1 or more pairs of electrons
typically very strong· almost all substances that make up organisms are held together by covalent bonds
Ch. 4 Chemistry Notes
Mixtures· a combination of 2 or more substances that are not chemically combined· substances keep their individual properties· can be separated into parts by physical means· 2 types
heterogeneous - not uniformly mixed (oil and vinegar)homogeneous (aka solution) - uniformly mixed
(salt water)
Review Questions1. What is a compound?2. What are two ways electrons form chemical bonds? How are they different?3. What is a molecule? What kind of bonds do they form?4. What is a mixture?5. How are heterogeneous and homogeneous mixtures different?