General Chemistry Placement Test, With Complete Solutions Updated | .

General Chemistry Placement Test, With Complete Solutions Updated | . molecule two nonmetal atoms combined form a covalent compound called a diatomic molecules H2,O2,F2 Matter Anything that has mass and takes up space Element A substance that cannot be broken down into simpler substances Compound A pure substance made of two or more elements CHEMICALLY combined. Compound Can be decomposed by chemically Mixture A PHYSICAL blend of two or more components (aq) aqueous mixture, a substance is dissolved in water homogeneous mixture A mixture that is so evenly mixed that you can't see all of the different parts. Ex. Air, kool-aid heterogeneous mixture A mixture in which different materials can be seen easily. Ex. soil, chocolate chip cookies filtration process to separate a solid "precipitate" from a liquid sublimation phase change from (s) --> (g) empirical formula A formula showing the lowest whole number ratio of atoms in a compound. Can't be reduced. solid A state of matter that has a definite shape and a definite volume liquid A form of matter that flows, has constant volume, and takes the shape of its container Bromine (Br) and Mercury (Hg) only two liquids on the periodic table gas A state of matter with no definite shape or volume gas will uniformly and completely fill a container gases physical property most all nonmetals and group 18 physical property A characteristic of a substance that does not involve a chemical change. Ex. melting/boiling point, solubility, density, color, or hardness. properties used to identify or recognize matter (objects). chemical property describes how matter reacts when it changes chemically into another substances. Ex. reactivity with acid, base or with air to rust, flammability, decomposition. physical/phase change (s)-->(l)-->(g), diluting, crush, cut. Still same substance. Density A physical property. Specific to every element. Chemical symbol One capital letter, or a capital letter and a lower case letter together. Mass on upper left side, and atomic # on lower left side. Conservation of Mass Equal # of atoms on both sides of a chemical equation Democritus Greek philosopher that said all matter is made of tiny particles called "atomos" or atoms JJ Thomson used the cathode ray tube to discover electrons Rutherford Gold foil experiment: (atom is mostly empty space, atoms contains a dense, positively charged nucleus); discovered protons. Wave Mechanical Model Modern model of the atom, atoms have electrons in "orbitals" that are like clouds around the nucleus Bohr Model A model resembling planets revolving around the sun in orbits, useful in visualizing the structure of atoms. Proton A subatomic particle that has a positive charge and that is found in the nucleus of an atom. Mass = 1 amu Atomic number Equals the number of protons in the nucleus (never changes) Electron A tiny, negatively charged particle that moves around the nucleus of an atom. # of protons Equals # of electrons in a neutral atom Nucleus A region that is located at the center of an atom and contains most of the atom's mass (protons and neutrons) Neutrons neutral partical that has the same mass as a proton and is found in an atom's nucleus. Isotopes Atoms of the same element having different masses because they contain different numbers of neutrons. Principle Energy Levels energy levels of an atom "shells". Energy increases further from the nucleus valence electrons Electrons on the outermost energy level of an atom Lewis dot structures diagrams that show valence electrons as dots Bright line spectrum colors produced when electrons fall to a lower energy level and release energy in the form of light. Ions Atom or group of atoms(polyatomic) with a positive or negative electrical charge due to a loss or gain of electrons. Ex: Na+, Cl- , NO3- Mendeleev Created the first periodic table. Arranged elements by increasing atomic mass Modern Periodic Table elements are arranged in order of increasing ATOMIC NUMBER Groups of Periodic Table Columns represent elements that have the same number of valence electrons and share similar chemical and physical properties Periods of periodic Table Rows correspond with # of total principle energy levels "shells" (rings) Ionization Energy (IE) Energy required to remove an electron from an atom Electronegativity (EN) Atom's ability to attract and hold electrons. Metals malleable (made into thin sheets) and lustrous (shiny) good conductors of electricity and heat. Low IE and Low EN Metals High IE and High EN Nonmetals Nonmetals Elements that are poor conductors of heat and electric current. Most are gases, dull & brittle Metalloids Elements along the staircase. Have properties of both metals and nonmetals. Ex: Silicon Alkali Metals Group 1 on PT. One valence electron that is easily removed to form a POSITIVE IONS. Highly reactive and form stable compounds. Alkali Earth Metals Group 2 on PT. Two valence electrons, form +2 ions. reactive Halogens Group 17: Nonmetals 7 valence electrons in it's outermost shell. Very reactive. Many diatomic gases and Iodine solid