Question

1. please identify the violated rule in the orbital diagram below.

a. each orbital within a sublevel should get one electron of same spin before electrons are paired into the orbital.
b. electrons should fill from the lowest energy level and sublevel before filling higher energy levels and sublevels.
c. two electrons maximum can share an orbital if the electrons are spinning in opposite directions.
d. there are no violations – this diagram is correct.

1. which is the correct electron configuration for lead?

a. xe 6s² 4f¹⁴5d¹⁰ 6p²
c. xe 5s² 5f¹⁴5d¹⁰5p²
b. xe 6s² 5d⁹ 6p²
d. xe 6s² 4f¹⁴5d¹ 6p²

1. the idea of arranging the elements in the periodic table according to their chemical and physical properties is attributed to...

a. mendeleev.
c. bohr.
b. moseley.
d. ramsay.

1. what is the electron configuration for the al⁺³ ion?

a. 1s² 2s² 2p⁶ 3s²
d. 1s² 2s² 2p⁶
b. 1s² 2s² 2p¹
e. 1s² 2s² 2p⁶ 3s² 3p⁴
c. 1s² 2s² 2p⁶ 3s² 3p¹

1. as you move down the periodic table from carbon to tin, the ionization energy...

a. increases.
d. decreases.
b. remains the same.
e. is unpredictable.
c. increases then decreases.

1. how many significant figures are in 0.002080?

a. 4
c. 6
b. 5
d. 7

1. what is the percent of oxygen in h₂o?

a. .15.99%
c. 33%
b. 88.8%
d. 99.8%

1. which coefficients correctly balance the formula equation: nh₄no₂ → 1 n₂ + 2 h₂o?

a. 1, 2, 2
c. 2, 1, 1
b. 1, 1, 2
d. 2, 2, 2

Explanation:

1. Question 55: The 2p sublevel has paired electrons in two orbitals while the third 2p orbital is empty, violating Hund's Rule (option a), which requires single same-spin electrons in each orbital before pairing.
2. Question 56: Lead (Pb, atomic number 82) has a valid noble gas shorthand configuration of $[\text{Xe}] 6s^2 4f^{14}5d^{10} 6p^2$, so option a is correct.
3. Question 57: Mendeleev arranged elements by their chemical and physical properties into the first periodic table, so option a is correct.
4. Question 58: Neutral Al has configuration $1s^2 2s^2 2p^6 3s^2 3p^1$. $\text{Al}^{3+}$ loses 3 valence electrons, leaving $1s^2 2s^2 2p^6$, so option d is correct.
5. Question 59: Ionization energy decreases down a group as valence electrons are further from the nucleus, so option d is correct.
6. Question 60: Leading zeros are not significant; the digits 2,0,8,0 are significant, giving 4 total significant figures, so option a is correct.
7. Question 61:

Mass of oxygen in $\text{H}_2\text{O} = 16.00$ g/mol
Molar mass of $\text{H}_2\text{O} = 2(1.008)+16.00 = 18.016$ g/mol
Mass percent = $\frac{16.00}{18.016} \times 100 \approx 88.8\%$, so option b is correct.

1. Question 62: Balanced equation: $\text{NH}_4\text{NO}_2

ightarrow \text{N}_2 + 2\text{H}_2\text{O}$, so coefficients are 1,1,2, option b is correct.
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Answer:

1. 55. a. Each orbital within a sublevel should get one electron of same spin before electrons are paired into the orbital.
2. 56. a. $[\text{Xe}] 6s^2 4f^{14}5d^{10} 6p^2$
3. 57. a. Mendeleev.
4. 58. d. $1s^2 2s^2 2p^6$
5. 59. d. decreases.
6. 60. a. 4
7. 61. b. 88.8%
8. 62. b. 1, 1, 2