Regents Chemistry Test Preparation Practice

    Atomic Concepts

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    Base your answers to questions 12 on the information below and on your knowledge of chemistry.

    Before atomic numbers were known, Mendeleev developed a classification system for the 63 elements known in 1872, using oxide formulas and atomic masses. He used an R in the oxide formulas to represent any element in each group. The atomic mass was listed in parentheses after the symbol of each element. A modified version of Mendeleev’s classification system is shown in the table below.

    periodic-table, elements-in-the-periodic-table, atomic-concepts, atomic-models, historic-models fig: chem62013-exam_g16.png

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    Base your answers to questions 13 on the information below and on your knowledge of chemistry.

    A student compares some models of the atom. These models are listed in the table below in order of development from top to bottom.

    atomic-concepts, atomic-models, historic-models fig: chem62014-exam_g11.png

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    Base your answers to questions 14 on the information below and on your knowledge of chemistry.

    In the late 1800s, Dmitri Mendeleev developed a periodic table of the elements known at that time. Based on the pattern in his periodic table, he was able to predict properties of some elements that had not yet been discovered. Information about two of these elements is shown in the table below.

    physical-behavior-of-matter, states-of-matter fig: chem62018-exam_g25.png

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    Base your answers to questions 15 on the information below and on your knowledge of chemistry.

    Many scientists made observations of the elements that led to the modern Periodic Table. In 1829, Dobereiner found groups of three elements that have similar properties and called each of these groups a triad. Dobereiner noticed a relationship between the atomic masses of the elements in each triad. Triad 1, shown in the table below, consists of sulfur, selenium, and tellurium. The middle element, selenium, has an atomic mass that is close to the sum of the atomic masses of sulfur and tellurium, divided by 2.

    periodic-table, elements-in-the-periodic-table fig: chem82017-exam_g18.png

    The other triads shown in the table below demonstrate the same mathematical relationship.

    periodic-table, elements-in-the-periodic-table fig: chem82017-exam_g17.png

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