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AP Biology - Chapter 2 Flashcards

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10411821484AnionA negatively charged ion.0
10411821485AtomThe smallest unit of matter that retains the properties of an element.1
10411822025Atomic MassThe total mass of an atom, numerically equivalent to the mass in grams of 1 mole of the atom.2
10411822886Atomic NucleusAn atom's dense central core, containing protons and neutrons.3
10411825132Atomic NumberThe number of protons in the nucleus of an atom, unique for each element and designated by a subscript.4
10411825723CationA positively charged ion.5
10411826385Chemical BondAn attraction between two atoms, resulting from a sharing of outer-shell electrons or the presence of opposite charges on the atoms. The bonded atoms gain complete outer electron shells.6
10411826697Chemical EquilibriumIn a chemical reaction, the state in which the rate of the forward reaction equals the rate of the reverse reaction, so that the relative concentrations of the reactants and products do not change with time.7
10411827357Chemical ReactionThe making and breaking of chemical bonds, leading to changes in the composition of matter8
10411827745CompoundA substance consisting of two or more different elements combined in a fixed ratio.9
10411828679Covalent BondA type of strong chemical bond in which two atoms share one or more pairs of valence electrons.10
10411829251DaltonA measure of mass for atoms and subatomic particles; the same as the atomic mass unit, or amu.11
10411829252Double BondA double covalent bond; the sharing of two pairs of valence electrons by two atoms.12
10411829669ElectronA subatomic particle with a single negative electrical charge and a mass about 1/2,000 that of a neutron or proton. One or more electrons move around the nucleus of an atom.13
10411830470Electron ShellAn energy level of electrons at a characteristic average distance from the nucleus of an atom.14
10411831271ElectronegativityThe attraction of a given atom for the electrons of a covalent bond.15
10411831272ElementAny substance that cannot be broken down to any other substance by chemical reactions.16
10411832927EnergyThe capacity to cause change, especially to do work (to move matter against an opposing force).17
10411833214Essential ElementA chemical element required for an organism to survive, grow, and reproduce.18
10411833215Hydrogen BondA type of weak chemical bond that is formed when the slightly positive hydrogen atom of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule or in another region of the same molecule.19
10411833576IonAn atom or group of atoms that has gained or lost one or more electrons, thus acquiring a charge.20
10411834108Ionic BondA chemical bond resulting from the attraction between oppositely charged ions.21
10411834917Ionic CompoundA compound resulting from the formation of an ionic bond; also called a salt.22
10411834918IsotopeOne of several atomic forms of an element, each with the same number of protons but a different number of neutrons, thus differing in atomic mass.23
10411835239Mass NumberThe sum of the number of protons and neutrons in an atom's nucleus.24
10411835630MatterAnything that takes up space and has mass.25
10411836080MoleculeTwo or more atoms held together by covalent bonds.26
10411836484NeutronA subatomic particle having no electrical charge (electrically neutral), found in the nucleus of an atom.27
10411837266Nonpolar Covalent BondA type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.28
10411837267OrbitalThe three-dimensional space where an electron is found 90% of the time.29
10411837607Polar Covalent BondA covalent bond between atoms that differ in electronegativity. The shared electrons are pulled closer to the more electronegative atom, making it slightly negative and the other atom slightly positive.30
10411838451Potential EnergyThe energy that matter possesses as a result of its location or spatial arrangement (structure).31
10411839099ProductA material resulting from a chemical reaction.32
10411839100ProtonA subatomic particle with a single positive electrical charge, found in the nucleus of an atom.33
10411839723Reactive IsotopeAn isotope (an atomic form of a chemical element) that is unstable; the nucleus decays spontaneously, giving off detectable particles and energy.34
10411840031ReactantA starting material in a chemical reaction.35
10411840032SaltA compound resulting from the formation of an ionic bond; also called an ionic compound.36
10411840336Single BondA single covalent bond; the sharing of a pair of valence electrons by two atoms.37
10411841303Trace ElementAn element indispensable for life but required in extremely minute amounts.38
10411841304ValenceThe bonding capacity of a given atom; usually equals the number of unpaired electrons required to complete the atom's outermost (valence) shell.39
10411841910Valence ElectronAn electron in the outermost electron shell.40
10411842572Valence ShellThe outermost energy shell of an atom, containing the valence electrons involved in the chemical reactions of that atom.41
10411842864Van der Waals InteractionsWeak attractions between molecules or parts of molecules that result from transient local partial charges.42

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