University:
Cornell University
Course:
CHEM 1150 | The Language of Chemistry
Academic year:

2020
Views:

193

Pages:

3
Author:

Clint W.

Use this Review along with your NOTES and ASSIGNMENTS to study for the quest. Why were early ideas about matter often wrong? The philosophers/scientists did not have the tools or technology to test their ideas. True or False. If False, EXPLAIN why on the line below! 1 F Matter is indivisible. Atoms can be divided into protons, electrons, and neutrons. T Atoms of a specific element are different than those of another element. F In a chemical reaction, new atoms are made. Atoms are rearranged. T Ions are atoms with the same atomic number, but different charges. T Atoms combine to form compounds in simple whole-number ratios. F Isotopes are atoms with different atomic numbers and different number of electrons. Same atomic numbers and different number of neutrons. F An atom of nitrogen with 10 electrons has a +3 charge. 7 protons, 10 electrons = 3- charge F An atom's atomic number is always equal to the number of electrons it has. protons T To find the number of neutrons in a certain isotope, subtract the atomic number from the mass number. F ⁶³Cu (Copper-63) has 29 protons and 36 neutrons. 63 - 29 = 34 Why do scientists use the atomic mass unit (amu) instead of grams when expressing atomic mass? 13. Complete the following table: Subatomic Particle Mass (amu) Charge Proton 1 + Neutron 1 0 Electron 1/1840 - 14. Draw an atom of sodium below including a key for subatomic particle symbols. sodium atom with 11 protons, 12 neutrons, and 11 electrons 15. What is the difference between the mass number and the average atomic mass? Mass number is the total number of protons and neutrons in an atom (whole number). Average atomic mass is the average mass of all of the isotopes of an element (decimal). 16. Calculate the atomic mass of the element X and identify the element from the periodic table, knowing that it has the following isotopes: 1 ⁵⁴X (abundance: 5.9%) ⁵⁶X (abundance: 91.72%) ⁵⁷X (abundance: 2.1%) ⁵⁸X (abundance: 0.28%) (0.059 * 54) + (0.9172 * 56) + (0.021 * 57) + (0.0028 * 58) = 3.186 + 51.3632 + 1.197 + 0.1624 = 55.91 amu Element X is Iron (Fe) 17. Explain why certain elements go through the process of radioactive decay. Their nucleus is unstable. 18. The half-life of calcium-47 is about 5 days. About how much of a 100-gram sample of this isotope remains after 15 days? 15 days ÷ 5 days/half-life = 3 half-lives Half-lives 0 1 2 3 Amount remaining 100g 50g 25g 12.5g Answer: 12.5g 19. Complete the following table Chemical Symbol # of protons # of electrons # of neutrons Atomic # Mass # $^{55}_{25}Mn $ 25 25 30 25 55 35 80 Br + 35 34 45 35 80 11 23 Na 11 11 12 11 23 12 36 Mg 2+ 12 10 24 12 36

Chem Atomic Structure Practice Key

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