Chem121 StudyGuide Ch1_2

Chem121 StudyGuide Ch1_2 - Chemistry 121 Study Guide...

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Chemistry 121 Study Guide Chapters 1&2 1. Briefly distinguish between the following pairs of terms(define, compare/contrast: A. Mass and Weight Mass is the quantity of matter in an object, weight is the force mass experiences under the pull of gravity. B. Pure compound and Mixture Pure compounds are made up of two or more elements in fixed combination and composition. Mixtures have no fixed composition and may be composed of elements and/or compounds. C. Mass Number and Atomic Weight Mass number is the sum of the protons and neutrons in the nucleus of an atom. Atomic weight is the weighted average of all the naturally occurring isotopes of an element; know how to do this kind of calculation. D. Mass number and Atomic number Mass number is stated above. Atomic number is the number of protons in the nucleus of an element. E. Nucleon and Nucleus Nucleons are the particles found in the nucleus - protons and neutrons. The Nucleus is where the nucleons are found which represents the majority of all the mass of an atom. F. Density and Specific Gravity Density is the mass/unit volume of a material. Specific gravity is the density of an object compared to the density of water at the same temperature. Specific gravity is therefore unitless. G. Element and Compound Both are pure substances. Elements cannot be broken down further by chemical means, while compounds can be broken down into their component elements using chemical processes. H. Electron Affinity and Ionization Energy In one sense they are opposites, as ionization refers to : “ the loss of the outermost valence electron in a gas phase neutral atom”, whereas electron affinity is: “ The gaining of one electron by a gas phase neutral atom”. They are not truly opposites as they both start from the neutral atom state, ionization always requires the input of energy, affinity usually releases energy but not for column 2A and 8A. Both are essentially a measure of the strength to which an atom holds onto or attracts outermost electrons. 2. Dalton claimed that all atoms of a particular element are identical. This is both true and not true. Explain why
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Chem121 StudyGuide Ch1_2 - Chemistry 121 Study Guide...

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