Problem+Set+9

PROBLEM SET 9 SOLUTIONS

1. a) Down a group- atomic radius increases b) Across a group- atomic radius decreases (Shoshi Center) //Shoshi, change 1b to across a period, not a group (Matt C.)//

2a. When you move down to the next element in the group, another energy level is added because of the subsequent amount of protons added. This causes the 'n' value to increase which means that the electrons move farther away from the nucleus, thus increasing the radius. 2b. As you move across each period on the periodic table, the radius decrease. This is because the energy level remains the same, however you are adding more protons to the nucleus, so the electromagnetic force pulling the electrons in becomes larger, decreasing the size of the radius. (Daniel Newman)

3. a) Down a group- ionic radius increases b) Across a group- ionic radius decreases (Shoshi Center) //Shoshi, change 3b to across a period, not a group (Matt C.)//

4. Na-1s^2 2s^2....3s^1 Na+-1s^2 2s^2...2p^6 There is a missing orbital for the sodium ion. The energy level of 2 on the outer orbital for a sodium ion indicates a smaller atomic radius than a sodium atom with an outer orbital energy level of 3. (Matt C.)

5. Mg+2: 12-2=10 O-2: 8+2=10 So Mg ion and O ion have the same number of electrons but electrons will be pulled closer to the Mg+2 nucleus because it has more protons, causing them to be more attracted. Therefore Mg ion will have a smaller radius and O ion will have a larger radius. (Nadia H.)

6. a) Down a group- ionization energy decreases b) Across a group- ionization energy increases (Shoshi Center) //Shoshi, change 6b to across a period, not a group (Matt C.)// 7. a. We thought it was because the most stable were those with the fewest boxes? Not positive though - feel free to change. (Unknown contributor) Ionization potentials tend to increase while one progresses across a period because the greater number of protons (higher nuclear charge) attract the orbiting electrons more strongly, thereby increasing the energy required to remove one of the electrons. (Andrew Blank) Maybe elements near the top of the periodic table have fewer electrons that are repelling each other, and are therefore more stable than elements at the bottom. Heavier elements have more electrons that repel each other, so they "want" to form an ion more. (Kevin Ray) b. Ionization energy increases because the boxes become full. For example, 1s^2 2s^2 2p^2 has less ionization energy than 1s^2 2s^2 2p^6 because the last level is more complete, or in this case complete. (Natalie) Good thinking there! Just to add on, like you said, the Ne atom with a configuration of 1s^2 2s^2 2p^6 has a higher ionization energy because it is stable; it takes more energy to remove an electron than it would for a C atom with the configuration 1s^2 2s^2 2p^2, because Carbon isn't as stable. The atoms will all have protons pulling the electrons towards the nucleus, so it always takes some energy to remove them. However, on the left side of the table it takes the least energy because removing electrons brings the atom closer to having filled orbitals and being stable, but as you move to the right atoms need to gain electrons to become stable (with filled orbitals), not lose them, so it takes more energy. (Kathryn J.) To add another idea, perhaps it takes more energy to form ions on the right side of the periodic table because there are more protons. These protons are attracted to the electrons in the atom, making atoms with more protons require more energy to form an ion. (Kevin Ray)

8. a) Down a group-electronegativity tends to decrease b) Across a period-electronegativity tends to increase

9. The noble gases do not have values for electronegativities because they are very stable. The orbitals of each level for noble gases are filled, so they are in a stable state. Therefore they are extremely unlikely to gain electrons and form negative ions, which is what electronegativity measures. (Kathryn J.)