Chemistry Chapter 2 Test Questions – Flashcards
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| Atom |
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| extremely small particle of matter that retains its identity during a chemical reaction |
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| Dalton's atomic theory (1803) part 1 true/false |
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| "all matter is composed of indivisible atoms" false, atoms can be subdivided into electron, protons, neutrons |
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| Dalton's atomic theory (1803) part 2 true/false |
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| "an element is a type of matter composed of only one kind of atom, each atom of which has the same properties" false: isotopes of an element have different properties |
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| Dalton's atomic theory (1803) part 3 true/false |
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| "a compound is a type of matter composed of atoms of two or more elements and chemically combined in fixed proportions" true |
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| Dalton's atomic theory (1803) part 4 true/false |
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| atoms are not created, destroyed, or broken into smaller particles by any chemical rxn true |
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| Applications of Dalton's atomic theory: Law of conservation of mass |
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| total mass doesn't change during a chemical rxn |
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| Deductions from Dalton's atomic theory: Law of multiple proportions |
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| when 2 elements can form more than one compound, the masses of one element in these compounds (for a fixed mass of the other element) are in small whole number ratios ex: carbon monoxide has 1.3321g O for 1g C carbon dioxide has 2.6642g O for 1g C |
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| discovery of the electron (1897) by whom? how? significance? |
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| JJ Thompson with the cathode ray tube; -cathode rays composed of negatively charged particles (deflected toward positive plate) -cathode rays are independent of the gas and material of electrodes -determined mass-to-charge ration, Me/e=5.6x10^-12 kg/C; called particle electron |
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| Oil drop experiment (1909) who? significance? |
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| -Robert Millikan -determined value of charge of electron: e=1.602x10^-19 C -w/ Thomson's data, mass of electron is determined to be approximately 1/1800 other mass of the lightest atom (H, a proton) mH = 1.674x10^-27 kg |
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| nuclear model of the atom: rocks and photographic plates (1896); who? significance? |
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| Henri Bequerel rocks overexposed his photographic plates, therefore the rocks were producing light, therefore were radioactive |
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| nuclear model of the atom: Marie Curie said? |
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| "radioactivity" shows that atoms are made of smaller particles |
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| nuclear model of the atom: splitting radiation (1903) who? significance? |
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| Rutherford; showed alpha particles were He2+ ions and B-rays were electrons -alpha radiation showed nucleus changing, therefore atoms are not unchangeable atoms |
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| nuclear model of the atom: Gold foil experiment (1909) who? sig? |
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| hans geiger and ernest marsden; found approx. 1 in 8,000 a-particles scattered. this was used for the basis of Rutherford's nuclear model |
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| Rutherford's nuclear model (1911) |
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| -nucleus is positively charged -nucleus is small compared to the atomic diameter (10^-10 m versus 10^-15m) |
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| Rutherford (1911): when a-particles collide w nitrogen and other gases, ______ form? |
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| hydrogen nuclei (protons) |
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| Bothe and Becker (1930) |
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| when a-particles struck beryllium target, strongly penetrating radiation was produced |
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| James Chadwick (1932) |
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| showed that some radiation consistes of a neutral particle with a mass approx. that of a proton (neutrons) |
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| nucleus |
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| core of atom comprises most of the mass of atom, along w one or more units of positive charge |
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| electron |
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| neg charge particle very light exists in region around positive nucleus |
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| proton |
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| positively charged particle equal in magnitude but opposite charge of electron mass is 1836 times that of electron, nearly the same as neutron's |
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| neutron |
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| no charge mass nearly identical to proton's |
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| atomic number: symbol, definition |
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| Z number of protons in nucleus (determines chemical identity of the atom) |
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| mass number: symbol; def |
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| A number of protons + neutrons (protons and neutrons give particle its mass) |
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| isotopes |
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| atoms of a element with same number of protons but differing number of neutrons |
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| nuclide symbol |
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| distinguishes isotopes of an element A/Z X X= element symbol |
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| mass spectrometer |
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| can separate different isotopes of an element; one can obtain percent abundance of isotopes by calculating the relative peak areas |
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| C-12 = X atomic mass units? |
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| c-12 has a mass of exactly 12 amu |
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| 1 amu= ? |
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| 1/12 mass of C-12 atom |
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| atomic weight |
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| the weighted average of the isotopic weights of an element, based on the isotope's relative natural abundance |
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| mole: def; number |
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| number of C-12 atoms in exactly 12g of C-12; 6.022x10^23 |
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| molar mass (MM) |
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| mass of one mol of a substance; is mass is in grams, MM is numerically equal to atomic weight in amu's. |
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| types of decay: alpha emission (a) symbol? changes in A or Z? |
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| 4/2 He, 2 protons, 2 neutrons daughter has 2 less protons (Z parent-2), and 2 less neutrons (A parent -4) |
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| beta emission (B) equivalent to? change in A or Z? |
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| 0/-1 e, one electron, equivalent to the conversion of a neutron to a proton (therefore, atomic number goes up one (Z parent +1); mass number does not change, A parent= A daughter) |
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| positron emission (B+) equivalent to? change in A or Z? |
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| 0/1 e a positively charged electron, equivalent to the conversion of a proton to a neutron; daughter has one less proton (therefore Z parent-1 = Z daughter), and A doesn't change (A parent = A daughter) |
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| electron capture (EC) |
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| 1/1 P + 0/-1 e --> 1/0 n occurs when a nucleus captures an inner orbital e- equivalent to proton and electron combining to make a neutron; A parent = A daughter; Z daughter = Z parent-1; will see emission of X ray photon |
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| Gamma emission (Y) |
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| 0/0 Y (a photon) radioactive decay may result in a daughter nucleus in an excited state (metastable nucleus); nucleus relaxes to a lower energy state by emission of a Y-photon; |
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| metastable nucleus (m) |
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| nucleus with an excited state lifetime less than or equal to 10^-9s |
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| substances |
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| cannot use physical means to separate a substance into other kinds of matter; possess definite intensive physical and chemical properties |
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| element |
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| cannot be decomposed by any chemical means into simpler substances |
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| compounds |
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| composed of more than one element, chemically combined; law of definite proportions: a pure compound, no matter its source always contains definite, constant proportions of the elements by mass ex: NaCl from china is the same as NaCl from clinton |
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| mixtures |
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| can be separated with psychical means into two or more substances |
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| heterogenous mixture |
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| a mixture consisting of physically distinct parts (phases) ex: oil and vinegar |
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| homogenous mixture (SOLUTION) |
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| a mixture that is uniform throughout ex: salt water |
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| chemical formulas |
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| notation for chemical compounds based on atomic symbols with subscripts indicating the relative proportions of the atoms in the substance; recall law of definite proportions; ex: Fe2O3 = 2Fe: 3O; H2O = 2H: 1O; NaCl= 1Na:1Cl |
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| molecular substance |
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| a definite group of atoms that are chemically bonded together; covalent bond (2/more atoms sharing electrons, usually a pair); can be notated by molecular formulas, structural formulas, molecular models |
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| some elements are molecular substances; list them. |
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| H. Bronclif; H2, Br2, O2, N2, Cl2, I2, F2 |
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| ionic substance |
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| composed of ions held together in a regular arrangement in space by the attraction of their opposing charges (Ionic bond) ex: NaCl crystal |
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| ion |
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| electrically charged particle obtained by adding or removing electrons from an atom or chemically bonded group of atoms |
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| cation |
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| positively charged ion formed by the loss of electrons from neutral atoms |
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| anion |
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| negatively charged ion formed by the gain of electron by a neutral atom |
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| ionic substance |
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| expressed in terms of smallest unit (formula unit); given that all substances are electrically neutral, we can deduce the formula for an ionic compound; ex: Cl- ions + Ba2+ ions formula unit = BaCl2 |
