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COMPETENCY GOAL 3

The History of the Table. Dobereiner (early 1800's): triads.Newlands (1865): atomic mass and octaves.Meyers and Mendeleev (1869): based on atomic mass and columns with similar properties.Moseley (1913): based on atomic number.. The Periodic Law. When elements are arranged in order of increasi

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COMPETENCY GOAL 3

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    1. COMPETENCY GOAL 3 JACK BRITT HIGH SCHOOL

    2. The History of the Table Dobereiner (early 1800’s): triads. Newlands (1865): atomic mass and octaves. Meyers and Mendeleev (1869): based on atomic mass and columns with similar properties. Moseley (1913): based on atomic number.

    3. The Periodic Law When elements are arranged in order of increasing atomic number, their physical and chemical properties show a periodic pattern.

    4. The Organization Groups or families and periods. Family names. Groups – similar properties. Vertical columns vs. horizontal rows. Metals (transition & inner transition), nonmetals, and semi-metals.

    5. Electron Configuration Electrons in the highest principle energy level = Outermost electrons = Valence electrons Elements in a group have similar properties because they have valence electrons in a similar configuration. Abbreviated electron configuration using the noble gas inner core. Four blocks (s, p, d, and f).

    6. Periodic Trends A systematic variation in the properties of elements going down a group or across a period. Atomic radius. Ionic radius. Ionization energy. Electronegativity.

    7. Atomic Radius The distance from the center of an atom’s nucleus to its outermost electron. Atoms get larger going down a group. Atoms get smaller moving from left to right across each period.

    8. Ionic Radius Atom loses electrons = positive ion = smaller. Atom gains electrons = negative ion = larger. Ion trend (Left vs. Right side).

    9. Ionization Energy The energy needed to remove one of an atoms electrons. Measure of how strongly an atom holds onto its outermost electron. Ionization energies decrease as you move down a group. Ionization energies increase as you move from left to right across a period. Opposite the atomic radius trends.

    10. Electronegativity Reflects the ability to attract electrons in a chemical bond. Related to its ionization energy and electron affinity. Increases as you move from left to right and decreases as you move down.

    11. “The Bridge”

    12. Molar Mass Distribute the subscript outside the ( ). List the elements in the compound. List the number of atoms for each. Look up the atomic mass for each and multiply by the number of atoms. Include significant figures and scientific notation as required.

    13. Mole Conversions Mass to moles. Moles to mass. Moles to particles. Particles to moles. Volume.

    14. Diatomic Molecules H2 N2 O2 F2 Cl2 Br2 I2

    15. Indicators of a Chemical Reaction Formation of a precipitate. Evolution of a gas. Color change. Absorption or release of heat.

    16. STOICHIOMETRY - EQUATIONS Stoichiometry: the study of quantitative relationships that exist in chemical formulas and reactions.

    17. The Process Balance the equation. Identify the known and unknown. Convert the known units to moles Multiply by mole ratio. Moles of unknown / moles of known Convert the moles of unknown to the desired units.

    18. % Composition The mass of each element in a compound compared to the entire mass of the compound. Solve for the molar mass Solve for each element using the formula: part X 100 whole The sum of the percentages should equal 100%. Example.

    19. Empirical Formula A formula that gives the simplest whole number ratio of the atoms of the elements. %: Assume 100g and convert all % signs to grams. Convert grams of elements to moles. Divide all the elements by the lowest # of moles to get the ratio. Write the empirical formula. Rounding: 0.01-0.44 round DOWN 0.45-0.55 multiply by 2 0.56-0.99 round UP

    20. Empirical Formula A formula that gives the simplest whole number ratio of the atoms of the elements. Determine the empirical formula for the compound that contains 80.38 % Bi, 1.16 % H, and 18.46 % O.

    21. Molecular Formula The formula that gives the actual # of atoms of each element in a molecular compound. The molecular formula is a multiple of the empirical formula.

    22. Molecular Formula The formula that gives the actual # of atoms of each element in a molecular compound. The molecular weight is 466.0 g and the empirical formula is C2H4O1. Determine the molecular formula. A compound is analyzed and determined to have an empirical formula of C6H8O and a molar mass of 290 g/mol. What is the molecular formula?

    23. Empirical and Molecular Formulas Determine the empirical formula for compounds that have the following analyses: 60.9% As and 39.1% S. 76.89% Re and 23.12% O. A 2.65 g sample of a salmon-colored powder contains 0.70 g of chromium, 0.65 g of sulfur, and 1.30 g of oxygen. The molar mass is 392.2. What is the formula of the compound? Determine the molecular formulas for compounds having the following empirical formulas and molar masses: C2H4S; molar mass 179g. C2H3O2; molar mass 119g.

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