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| 7373174769 | Atom | Smallest unit of matter that still retains properties of an element | 0 | |
| 7373211936 | Neutrons | No charge, in nucleus | 1 | |
| 7373220425 | Protons | Positive charge, in nucleus, number determines atomic number | 2 | |
| 7419818693 | Electrons | Negative charge, orbit nucleus, when the number of them is different from number of protons the atom becomes an ion | 3 | |
| 7419825005 | Atomic number | Number of protons | 4 | |
| 7419827062 | Mass number | Number of protons plus neutrons | 5 | |
| 7419828907 | Essential elements | Required by organisms, 20-25% of 92 natural elements, CHON make up 96% of living matter and other include Ca, P, K, S, and others | 6 | |
| 7419846863 | Trace elements | Only required in minute quantities | 7 | |
| 7419849707 | Compound | 2+ elements combined in a fixed ratio | 8 | |
| 7419860163 | Ions | Atoms that have a charge | 9 | |
| 7419862088 | Cation | Positive charge (lost electrons) | 10 | |
| 7419862089 | Anion | Negative charge (gained electrons) | 11 | |
| 7419865118 | Isotopes | Atoms with a different number of neutrons, radioactive ones are used in biological research | 12 | |
| 7419873324 | Electron shell/energy level | Electron's state of potential energy, electrons can move up/down levels by absorbing/releasing energy | 13 | |
| 7419878520 | Valence shell | number of electrons in it determines chemical behavior, reactivity of an atom arises from the presence of 1+ unpaired electrons in valence shell | 14 | |
| 7419891405 | Covalent bonds | 2+ atoms held together by valence bonds to make a molecule | 15 | |
| 7419896398 | Electronegativity | an atom's attraction for the electrons in a covalent bond | 16 | |
| 7419900547 | Nonpolar covalent bond | atoms share electron equally | 17 | |
| 7419900549 | Polar covalent bond | 1 atom is more electronegative, electrons not shared equally (causes partial positive/negative charge) | 18 | |
| 7419909316 | Ionic bond | Transfer of electrons from one atom to another to result in full valence shells gives them opposite charges (anion and cation), the are attracted and bond together | 19 | |
| 7419917569 | Hydrogen bond | Hydrogen atom covalently bonded to one electronegative atom has a partial charge, attracts to other nearby electronegative atoms with opposite partial charges | 20 | |
| 7419935381 | Van der Waals interaction | asymmetrical electrons can result in "hot spots" of +/- charge, this is when these charges cause molecules that are close together to attract | 21 | |
| 7419942141 | Molecular shape | determines how biological molecules recognize and respond to one another, molecules with similar shapes can have similar biological effects (e.g. pain relievers bind to endorphin receptors, artificial sweeteners) | 22 | |
| 7419949185 | Chemical reactions | making and breaking of chemical bonds, reactants become products, always reversible | 23 | |
| 7419955382 | Chemical equilibrium | The forward and reverse reaction rates are equal | 24 | |
| 7419958060 | Polarity of water | Oxygen has a partial negative charge and hydrogen has a slight positive charge, two water molecules are held together by hydrogen bonds | 25 | |
| 7419972716 | 4 properties of water that make earth suitable for life | cohesive behavior, ability to moderate temperature, expansion upon freeing, versatility as a solvent | 26 | |
| 7419980135 | cohesion/adhesion | Water is linked by hydrogen bonds and therefore stay close together, used to "walk up" the trunk of a tree | 27 | |
| 7419985444 | Ability to moderate temperature | water absorbs heat from warmer air and releases stored heat to cooled air, resists changing its temperature because of its high specific heat | 28 | |
| 7419998610 | Water as a solvent | Water is a versatile solvent because of its polarity (easily forms hydrogen bonds), dissolves ionic compounds by surrounding ions in hydration shell, can also dissolve nonionic polar molecules | 29 | |
| 7420006043 | Hydration shell | Ions surrounded by a sphere of water molecules | 30 | |
| 7420008217 | Hydrophilic | Has an affinity for water; polar | 31 | |
| 7420010567 | Hydrophobic | Doesn't have affinity for water; nonpolar (e.g. oil) | 32 | |
| 7420018050 | Acids and bases | Disrupt balance between H+ and OH- in pure water, acids increase H+ concentration in water while bases reduce concentration of H+ | 33 | |
| 7420032275 | pH of a solution | negative logarithm of H+ concentration (e.g. 10^-4), acids have pH<7 and bases have pH>7 (STD is 7) | 34 | |
| 7420043191 | Buffers | substances that minimize changes in concentration of H+ and OH- in a solution (e.g. pancreas releases substances that neutralizes acid chyme) | 35 |
