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?