**CHEMISTRY MIDTERM STUDY GUIDE** Student Copy – Flashcards
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Chemistry
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the study of matter and the changes it undergoes
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Matter
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anything that has mass and takes up space
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Mass
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the amount of matter contained
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Volume
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the amount of space the object occupies
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Density
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relationship between mass and volume
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pure substance
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matter with a uniform and definite composition
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element
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simplest form of matter; cannot be broken down
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compound
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two or more elements chemically combined
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atom
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smallest unit of matter
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Elements have unique ____ and are represented by ____ ____.
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properties, chemical symbols
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Symbols of elements are 1-2 ____.
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letters
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If there are 2 letters representing an element only the 1st is ____.
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capitalized
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Compounds have a fixed ____ and are represented by _____ _____.
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proportion; chemical formulas
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Subscripts of compounds show the ___ of elements in the compound.
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proportion
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Compounds can't be broken down ______, only _____.
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physically, chemically
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physical properties
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properties observed without changing the substance's composition
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The state of matter is a _____ property.
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physical
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physical change
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doesn't change the identity of the substance (ex: grinding, melting, boiling)
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chemical properties
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properties that describe how substances react to form new substances
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mixture
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physical blend of 2 or more substances
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heterogeneous mixture
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composition is not uniform throughout
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homogeneous mixture
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composition is uniform throughout
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Separating mixtures can be done based on ____ properties.
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physical
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Filtration
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separation technique involving solid & liquid; based on size; pass through pores
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Distillation
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separation technique involving different liquids based on boiling points
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Crystallization
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separation technique involving solid & liquid; based on evaporation; one thing evaporated leaving solid behind
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chemical change
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forming of new substances (iron --> rust)
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Alchemy
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...a form of chemical science and philosophy practiced in the Middle Ages
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Conductivity
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...ability to transmit heat or electricity
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Ductile
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...ability to be shaped into wires
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intermolecular forces
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...forces of attraction between molecules
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Malleability
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...ability to be shaped or changed
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Solubility
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...ability to dissolve in water
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Atomic Mass Unit
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A unit of mass that describes the mass of an atom or molecule. (amu)
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Atomic Number
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Number of protons in an atom
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Average Atomic Mass
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weighted average of the atomic masses for the isotopes of an element
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Isotopes
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Atoms of the same element that have different numbers of neutrons.
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Mass number
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Sum of protons and neutrons (the rounded atomic #)
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Bohr
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Came up with the Planetary Model
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Compound
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A substance made up of atoms of two or more different elements joined by chemical bonds
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Dalton's atomic theory
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1-Elements are made up of atoms 2-All atoms of a given element are identical 3- the atoms of an element are different from every other element 4-atoms of an element can combine to form a compound 5-atoms are invisible in the chemical process and they are not created or destroyed
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Electron
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A subatomic particle that has a negative (-1) charge and almost no mass
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Electron configuration
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The arrangement of electrons in an atom 2 in the first shell, eight in the second shell, 8 in the 3rd shell
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Group/family
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Column of the periodic table read from top to bottom Elements of the same group have similar properties and have the same number of valence electrons
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Ion
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An atom with a charge
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An ion with the SAME number of p+ and e- charges is a...
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Neutral atom
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Metal
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Elements that are good conductors of heat and electric current because their electrons are loosely bound Positive charge Lose electrons
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Metalloid
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Elements with properties that fall between those of metals and nonmetals
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Modern atomic model
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Atom consists of a nucleus that contains protons and neutrons surrounded by an electron cloud
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Neutron
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A subatomic particle that has no charge and is found in the nucleus of an atom Has a mass of 1 amu
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Nonmetals
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Group of elements that may be solids, liquids, or gases at room temp and tend to be poor conductors of heat and electricity, and NOT malleable, ductile, or lustrous Negative charge Gain electrons
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Nucleus
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The positively charged center of an atom Contains protons and neutrons
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Period
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Runs horizontally Read from left to right Elements in any period are putting electrons in the same valence shell
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PEriodic Table
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A chart of elements showing the repeating pattern of their properties, arranged in order of increasing atomic number
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A positive ion has
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More protons (positive charges) than electrons (negative charges)
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Rutherford
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Experimented with gold foil and discovered that a particle inside the nucleus could deflect the beam directed at it -Positive nucleus (because some alpha particles bounced back) -Mostly empty space (because most particles kept going through)
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Stable Octet
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8 valence electrons (unless the element only has one shell, then it's 2)
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Thompson
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Scientist from Britain who thought the electrons in his model reminded him of plum pudding
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Three classes of elements
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metal, nonmetal, metalloid
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To find the # of neutrons in an atom...
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Round the atomic weight of the atom then subtract the # of protons (Mass-atomic number)
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Valence electrons
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Electrons in the last shell of an atom
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Radioactive
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When UNSTABLE isotopes give off radiation due to spontaneous decay of the nucleus
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Nuclear Reaction
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Protons and neutrons are rearranged or released from the nucleous, tremendous amount of energy released
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Natural Transmutation
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Elements that naturally emit energy without the absorption of energy from an outside source (can be found on table N) (The radioactive isotope will be a product, there will be only one reactant)
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Artificial transmutation
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Causes an otherwise stable nucleus to become radioactive (ex: nuclear fission and nuclear fusion) (The radioactive isotope will be a reactant/come before the arrow)
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Alpha particle
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A helium nucleus emitted by a radioactive isotope
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Beta particle
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A fast moving electron emitted by radioactive decay of substances
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Positron
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A subatomic particle that has the same mass as an electron but has a positive charge
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Half life
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The time it takes half of a radioisotope to disintegrate
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Nuclear fission
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Splitting of a heavy nucleus into 2 lighter nuclei
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Nuclear fusion
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Combining of 2 light nuclei to form 1 nucleus of larger mass
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Gamma radiation
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penetrating electromagnetic radiation emitted by radioactive decay of substances
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Transmutation
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The changing of one element into another radioactive decay or nuclear bombardment
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Bright Line Spectrum
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The light that is emitted due to electrons moving from excited state back down to ground state
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Electron Shell
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The energy level that an electron is in; shown as circles around the nucleus
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Ground State Electron Configuration
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representation of the arrangement of electrons around the nucleus when in ground state
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Excited State Electron configuration
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when one electron jumps from a lower shell to a higher shell ie: 2-8-5 in ground state could become 2-7-6 in the excited state
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Valence electron
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Electrons in the last shell that are involved in chemical reactions
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Octet rule
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All electron shells need 8 electrons in order to be stable (except the first shell, which needs 2)
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Lewis dot diagram
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Diagram that has the chemical symbol and the valence electrons around it
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Noble gases
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elements found in group 18 that are most stable (non reactive) because they have 8 valence electrons (full shell/octet)
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Ion
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A charged atom formed by the loss or gain of electrons -Loss of electrons: positive ion -Gain of electrons: negative ion
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Cation
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A positive ion due to the loss of electrons
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Anion
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A negative ion due to the gain of electrons
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Ionization Energy
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The amount of energy required to remove an electron from an atom to form a cation (found in table S)
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Atomic radius
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The size of an atom, meaning the distance from the center of the nucleus to the outermost stable electron shell
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Ionic radius
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the size of an ion, radius is smaller for cations and greater for anions
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Ionic Bond
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-Bond that is formed when a metal TRANSFERS electrons to a nonmetal
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Ionic Compound
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Metal atom and nonmetal atom that are chemically combined
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Chemical Formula
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A set of chemical symbols showing the elements and their number of atoms present in a compound
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Subscript
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Small number written slightly below element symbols that represent the number of atoms present
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Criss cross
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Method used to find the chemical formula for an ionic compound
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Polyatomic ion
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Two or more atoms covalently bonded that act as a single unit (family) and have a charge Table E
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Transition Metal
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Any of the metallic elements within group 12 through 12 on the Periodic table The Roman Numeral represents the charge!
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Covalent bond
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The bond created between two or more nonmetals by the SHARING of electrons
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Covalent Compound
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2 or more nonmetals that are chemically combined Also called MOLECULAR COMPOUND
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Molecular Compound
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Aka Molecule Another name for a covalent compound (2 or more nonmetals)
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Prefix
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-only used for covalent compounds -Mono (1) -Di (2) -Tri (3) -Tetra (4) -You don't put "mono" before the first element in the compound (ex: CO is carbon monoxide, NOT monocarbon monoxide)
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Lone pair
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A pair of valence electrons that are not shared with another atom in a covalent bond
