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ChemistrySC:Ch. 2
Atoms, Molecules, and Ions
| Term | Definition |
|---|---|
| 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 unit, u, or Dalton, Da) unit of mass equal to 1/12 of the mass of a C-12 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 x 10 to the -9 C |
| group | vertical column of the periodic table |
| halogen | element in group 17 |
| 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 substance compound contain the same elements in the same proportions |
| 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 columns 1, 2, and 12-18 |
| 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 columns 3–11 |
| unified atomic mass unit (u) | alternative unit equivalent to the atomic mass unit |
| In the 5th century BC, what did Leucippus and Democritus argue? | They argued that all matter was composed of small, finite particles that they called atomos; thought of atoms as moving particles that differed in shape/size, and could join together. |
| What did Aristotle and other philosophers think about matter? | Concluded that matter consisted of various combinations of the four elements: fire, water, air, earth; these were philosophical concepts and were not tested |
| When was Dalton´s Atomic Theory published? | First published in 1807 |
| What was the first postulate of Dalton´s Atomic Theory? | Matter is composed of exceedingly small particles called atoms, which are the smallest unit of an element that can participate in a chemical change |
| What was the second postulate of Dalton´s Atomic Theory? | All elements consist of only one type of atom, which has a mass that is characteristic of the element and is the same for all atoms of that element |
| What was the third postulate of Dalton´s Atomic Theory? | Atoms of one element differ in properties from atoms of all other elements |
| What was the fourth postulate of Dalton's Atomic Theory? | A compound consists of atoms of two or more elements combined in a small, whole-number ratio; in a compound, the number of each of its elements are always present in the same ratio |
| What was the fifth postulate of Dalton´s Atomic Theory? | Atoms are neither created nor destroyed during a chemical change, but are instead rearranged to yield substances that are different from those present before the change |
| What does Dalton´s atomic theory provide? | It provides a microscopic explanation of the many macroscopic properties of matter |
| Who was responsible for the Law of Definite Proportions? | French chemist Joseph Proust |
| Are different compounds but same ratio the same substance? | No, samples that have the same mass ratio are not necessarily the same substance |
| Who invented the cathode ray tube? | English physicist J. J. Thomson |
| What was J. J. Thomson´s conclusion on his experiments with the cathode ray tube? | The particles are attracted by positive charges and repelled by negative charges (like charges repel and unlike charges attract) |
| What did J. J. Thomson´s cathode ray particle eventually turn into? | His cathode ray is what we now call an electron, a negatively charged, subatomic particle w/ a mass more than one thousand-times less that of an atom |
| Who uncovered more information about the electron in 1909? | In 1909, American physicist Robert A. Millikan uncovered more info. about the electron through his "oil drop" experiment |
| What did Millikan conclude in his "oil drop experiment"? |
Created by:
Siegmund_Agarrado
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