POGIL Answer Keys

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Average Atomic Mass1. 122. 24, 25, and 263. No, some have more mass that the others4. Mass 24 – 16

Mass 25 – 2Mass 26 – 2

5. 24Mg6. Mass 24 – 8

Mass 25 – 1Mass 26 – 1

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7a. Mass 24 – 16Mass 25 – 2Mass 26 – 2

7b. It matches the model in Model 18. 24 amu – as that has the greatest

abundance9a. 24.3069b. No10a. It would be too much to squeeze into one box10b. As the physical and chemical properties of isotopes are the same it is not usually important to scientists.

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11. Mary’s method = 24.305 amuJack’s method = 24.305 amuAlan’s method = 24.984 amu

12a. Mary and Jack12b. Alan’s method incorrectly weights all the isotopes the same13. 15.999 amu14a. 24Mg14b. As 24Mg is the most abundant the weighted average will be closest to 24Mg15. As the average mass is 10.81 boron-11 must be most abundant.

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16a. Yes16b. No, as the composition is identical16c. The bonding between the atoms makes the difference.17. Allotrope – same composition, but different characteristics because of different bonding

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Coulombic Attraction1. + = proton, - = electron2. Attraction3. As distance increases the force of

attraction decreases.4. Less than5. Greater than6a. The force of attraction6b. The strength7a. It increases7b. In decreases8. More protons make for a larger force9. 11.5 x 10-8 N10. It should decrease

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11. Row12. 13. Chlorine14a. No14b. No14c. Na = 11, Al = 13, Cl = 1714d. Yes – more protons means more attraction15a. Ca15b. Cu15c. Ar16a. Li = 3, Na = 11, K = 1916b. Distance as the force of attraction decreases while also having more protons

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17a. Inverse17b. Direct 2 / x

Electron Energy and Light1. Shades of the color2. Yes3. Violet = highest4. red = lowest5a. Red5b. Violet5c. Wavelength is inversely related to frequency6. There are lines that are different7. Attract8. Attraction, stonger9. Gain10.Lose

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11. Absorbed to travel farther fromthe nucleus

12a. Picture B12b. Releases12c. Higher, lower12d. Released13.

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14a. n = 6 to n = 214b. The greater change in distance means the greater change in energy.15. It only has 1 electron16. Many, many H atoms each with their electrons making different transitions.17a. n = 7, 6, 5, 4, 3, or 2 to n=117b. n = 7, 6, 5, or 4 to n = 318a. Li and Na are not present18b. H and He are present19. Emission and absorption spectrum would have lines at the same energies (wavelengths) but one is emitted lines (bright lines of color) and one absorbed lines (lines of black within the rainbow)

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Periodic Trends1a. The first number1b. pm1c. The size of the atom (from center of nucleus to valence energy level)2. Atomic radius increases3. The atomic radius increases as the number of energy levels increases4. Atomic radius decreases5. The effective nuclear charge increases and pulls the electrons closer6a. It takes energy to pull apart attracted particles6b. Tight = more energy

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7. Ionization energy decreases8. The farther distance between the nucleus and the electrons means less energy needed to remove the electron.9. Ionization energy increases10. The greater effective nuclear charge requires more energy to remove electrons11. Metals should have low ionization energy, so the electrons are easy to move allowing for high conductivity, malleability, and ductillity.12. Diagram B

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13a. Electronegativity decreases13b. The increased distance means the nucleus of one atom is farther from the electrons of the other atom, so it has a weaker attraction.13c. It increases13d. The greater effective nuclear charge allows the nucleus to pull with greater attraction.14. (on the left)= Electronegativity and I.E.

(on the right)= atomic radius

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15a. Skip(IE of O is less than N)

15b. Skip(Oxygen’s last electron is in an orbital

already containing an electron, so the increase of electron-electron repulsion between the electrons make it easier to remove, even with more effective nuclear charge)16. Ba, Fe, Br

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