2.9: Key Terms
- Page ID
- 452418
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| Words (or words that have the same definition) | The definition is case sensitive | (Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages] | (Optional) Caption for Image | (Optional) External or Internal Link | (Optional) Source for Definition |
|---|---|---|---|---|---|
| (Eg. "Genetic, Hereditary, DNA ...") | (Eg. "Relating to genes or heredity") |  | The infamous double helix | https://bio.libretexts.org/ | CC-BY-SA; Delmar Larsen |
| Word(s) | Definition | Image | Caption | Link | Source |
|---|---|---|---|---|---|
| actinide | inner transition metal in the bottom of the bottom two rows of the periodic table | ||||
| alkali metal | element in group 1 | ||||
| alkaline earth metal | element in group 2 | ||||
| alpha particle (α particle) | positively charged particle consisting of two protons and two neutrons | ||||
| anion | negatively charged atom or molecule (contains more electrons than protons) | ||||
| atomic mass | average mass of atoms of an element, expressed in amu | ||||
| atomic mass unit (amu) | (also, unified atomic mass unit, u, or Dalton, Da) unit of mass equal to of the mass of a 12C atom | ||||
| atomic number (Z) | number of protons in the nucleus of an atom | ||||
| binary acid | compound that contains hydrogen and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water) | ||||
| binary compound | compound containing two different elements. | ||||
| cation | positively charged atom or molecule (contains fewer electrons than protons) | ||||
| chalcogen | element in group 16 | ||||
| chemical symbol | one-, two-, or three-letter abbreviation used to represent an element or its atoms | ||||
| covalent bond | attractive force between the nuclei of a molecule’s atoms and pairs of electrons between the atoms | ||||
| covalent compound | (also, molecular compound) composed of molecules formed by atoms of two or more different elements | ||||
| Dalton (Da) | alternative unit equivalent to the atomic mass unit | ||||
| Dalton’s atomic theory | set of postulates that established the fundamental properties of atoms | ||||
| electron | negatively charged, subatomic particle of relatively low mass located outside the nucleus | ||||
| empirical formula | formula showing the composition of a compound given as the simplest whole-number ratio of atoms | ||||
| fundamental unit of charge | (also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 10−19 C | ||||
| group | vertical column of the periodic table | ||||
| halogen | element in group 17 | ||||
| hydrate | compound containing one or more water molecules bound within its crystals | ||||
| inert gas | (also, noble gas) element in group 18 | ||||
| inner transition metal | (also, lanthanide or actinide) element in the bottom two rows; if in the first row, also called lanthanide, or if in the second row, also called actinide | ||||
| ion | electrically charged atom or molecule (contains unequal numbers of protons and electrons) | ||||
| ionic bond | electrostatic forces of attraction between the oppositely charged ions of an ionic compound | ||||
| ionic compound | compound composed of cations and anions combined in ratios, yielding an electrically neutral substance | ||||
| isomers | compounds with the same chemical formula but different structures | ||||
| isotopes | atoms that contain the same number of protons but different numbers of neutrons | ||||
| lanthanide | inner transition metal in the top of the bottom two rows of the periodic table | ||||
| law of constant composition | (also, law of definite proportions) all samples of a pure compound contain the same elements in the same proportions by mass | ||||
| law of definite proportions | (also, law of constant composition) all samples of a pure compound contain the same elements in the same proportions by mass | ||||
| law of multiple proportions | when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small whole numbers | ||||
| main-group element | (also, representative element) element in groups 1, 2, and 13–18 | ||||
| mass number (A) | sum of the numbers of neutrons and protons in the nucleus of an atom | ||||
| metal | element that is shiny, malleable, good conductor of heat and electricity | ||||
| metalloid | element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals | ||||
| molecular compound | (also, covalent compound) composed of molecules formed by atoms of two or more different elements | ||||
| molecular formula | formula indicating the composition of a molecule of a compound and giving the actual number of atoms of each element in a molecule of the compound. | ||||
| monatomic ion | ion composed of a single atom | ||||
| neutron | uncharged, subatomic particle located in the nucleus | ||||
| noble gas | (also, inert gas) element in group 18 | ||||
| nomenclature | system of rules for naming objects of interest | ||||
| nonmetal | element that appears dull, poor conductor of heat and electricity | ||||
| nucleus | massive, positively charged center of an atom made up of protons and neutrons | ||||
| oxyacid | compound that contains hydrogen, oxygen, and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water) | ||||
| oxyanion | polyatomic anion composed of a central atom bonded to oxygen atoms | ||||
| period | (also, series) horizontal row of the periodic table | ||||
| periodic law | properties of the elements are periodic function of their atomic numbers. | ||||
| periodic table | table of the elements that places elements with similar chemical properties close together | ||||
| pnictogen | element in group 15 | ||||
| polyatomic ion | ion composed of more than one atom | ||||
| proton | positively charged, subatomic particle located in the nucleus | ||||
| representative element | (also, main-group element) element in columns 1, 2, and 12–18 | ||||
| series | (also, period) horizontal row of the period table | ||||
| spatial isomers | compounds in which the relative orientations of the atoms in space differ | ||||
| structural formula | shows the atoms in a molecule and how they are connected | ||||
| structural isomer | one of two substances that have the same molecular formula but different physical and chemical properties because their atoms are bonded differently | ||||
| transition metal | element in groups 3–12 (more strictly defined, 3–11; see chapter on transition metals and coordination chemistry) | ||||
| unified atomic mass unit (u) | alternative unit equivalent to the atomic mass unit |