Semester Exam Review Foothill Chemistry

Basic Chemistry Definitions Element - substance that cannot be changed into simpler substances by chemical means Compound - substance composed of two or more substances chemically combined in a fixed proportion Mixture - a physical blend of two or more components Homogeneous Mixture - describes mixture with a uniform composition Heterogeneous Mixture – describes mixture with a non-uniform composition Phase - part of a sample having uniform composition and properties

More Basic Chemistry Chemical Reaction - process in which substances are changed into different substances Reactant - starting substance in a chemical reaction Product - a substance formed in a chemical reaction Vapor - gaseous state of substance that is a liquid or solid at room temperature Distillation - a process in which a liquid is boiled to produce a vapor that is condensed again into a liquid

Atoms Atom - the smallest particle of an element that retains the properties of that element Mass - amount of matter an object contains Proton – positively charged subatomic particle Electron – negatively charged subatomic particle Neutron – subatomic particle with no charge Nucleus - the central part of an atom, containing protons and neutrons

Mass Mass Number – Protons + Neutrons Atomic Mass Unit – 1/12 of carbon-12 mass Atomic Mass – Weighted average mass of the atoms in a naturally occurring sample of an element Molar Mass – Mass of one mole of a substance in grams

Isotope Notation (Element Symbol) 1H 1H 12C 6C 13C 6C 14C 6C Mass Number Charge (Element Symbol) Atomic Number 1H 1H 12C 6C 13C 6C 14C 6C Atomic Number = Number of Protons in an atom (the element # on the Periodic Table) Mass Number = Number of Protons + Number of Neutrons in an atom Charge = Number of Protons – Number of Electrons in an atom Isotope - atoms with the same number of protons, but different numbers of neutrons in the nucleus of an atom

Ionic Compound Formed by the attraction of oppositely charged ions (Usually between Metal and Non-Metal) High melting point Called Salts Total of positive and negative charged ions must = 0

Covalent Compound Formed when elements share electrons Shared electrons are found in between the two elements Usually between two or more non-metals Also called molecular compounds Naming uses the mono-, di-, tri-, etc. prefixes

Significant Figures Multiplication – Smallest number of significant figures of all the terms Addition – Smallest number of digits after the decimal point of all the terms Left zeroes are not significant. Right zeroes before the decimal point are not significant unless there is a decimal point Right zeroes after the decimal point are significant Zeroes in the middle are significant

Ions Cation – Positive Ion Anion – Negative Ion Roman numeral gives the charge -ic suffix higher charge number / - ous lower charge number Anion – Negative Ion Monoatomic anions – end in –ide Make hydro[root]ic acids Polyatomic anions – end in –ite or –ate -ate ions have more oxygen than –ite ions -ite makes [root]ous acids -ate makes [root]ic acids

Hard Test Question What is the energy of a microwave photon that has a frequency of 1.12 x 1012 Hz? (h = 6.63 x 10-34Js) ? Make sure that your answer includes the correct number of significant figures and the correct units. Show your work for full credit.

Essay Questions Positive ions are smaller than the atoms from which they are formed, but negative ions are larger than the atoms from which they are formed. Explain why this is so. Explain how atoms (ions) are held together in an ionic bond. Give an example of an ionic compound. Explain what a polar molecule is. Provide an example. Explain the difference between chemical properties and physical properties. Give an example of each.

Other things to know Atomic Mass Calculation Formula Mass Calculation Molecular Mass Calculation Percent Composition Calculation Electron Configuration (Aufbau Diagram) Representative Elements = Group A Elements Valence Electron Determination