Question

q1 chemistry u2l17.5 unit 2 mini review

1. write the preferred charges of the following element and calculate the number of electrons the ion would have (hint: refer to your annotated periodic table to find the preferred charges)

element preferred charge total number of electrons
o -2 10 electrons (8 + 2)
**na
*mg
f
**n
li

1. **fill in the table with the number of orbitals and total number of electrons found in each sublevel.

sublevel # of orbitals total # of electrons
s
p
d
f

1. examine the orbital diagrams for an element to the right to answer the following questions:

a. **circle the correct orbital diagram.
b. **why is that one correct?
1s 2s 2p

1. ↑↓ ↑↓ ↑↓ ↑↓
2. ↑↓ ↑↓ ↑↓ ↑ ↑
3. ↑↓ ↑ ↑↓ ↑↓ ↑
4. ↑↓ ↑↓ ↑↓ ↑

Explanation:

Step1: Determine preferred charges and electron - counts for elements

• Sodium (Na) is in Group 1 of the periodic table. It loses 1 electron to achieve a stable noble - gas configuration. So the preferred charge is +1. The atomic number of Na is 11. When it forms a +1 ion, the number of electrons is 11 - 1=10.
• Magnesium (Mg) is in Group 2. It loses 2 electrons to achieve a stable noble - gas configuration. The preferred charge is +2. The atomic number of Mg is 12. When it forms a +2 ion, the number of electrons is 12 - 2 = 10.
• Fluorine (F) is in Group 17. It gains 1 electron to achieve a stable noble - gas configuration. The preferred charge is - 1. The atomic number of F is 9. When it forms a - 1 ion, the number of electrons is 9+1 = 10.
• Nitrogen (N) is in Group 15. It gains 3 electrons to achieve a stable noble - gas configuration. The preferred charge is - 3. The atomic number of N is 7. When it forms a - 3 ion, the number of electrons is 7 + 3=10.
• Lithium (Li) is in Group 1. It loses 1 electron to achieve a stable noble - gas configuration. The preferred charge is +1. The atomic number of Li is 3. When it forms a +1 ion, the number of electrons is 3 - 1 = 2.

Element	Preferred charge	Total number of electrons
Mg	+2	10
F	- 1	10
N	- 3	10
Li	+1	2

Step2: Fill in the orbital - sublevel table

• The s sublevel has 1 orbital. Each orbital can hold a maximum of 2 electrons, so the s sublevel can hold 2 electrons.
• The p sublevel has 3 orbitals. Since each orbital can hold 2 electrons, the p sublevel can hold 6 electrons.
• The d sublevel has 5 orbitals. With 2 electrons per orbital, the d sublevel can hold 10 electrons.
• The f sublevel has 7 orbitals. With 2 electrons per orbital, the f sublevel can hold 14 electrons.

Sublevel	# of orbitals	Total # of electrons
p	3	6
d	5	10
f	7	14

Step3: Determine the correct orbital diagram

• According to Hund's rule, electrons fill degenerate (equal - energy) orbitals singly first before pairing up. For the 2p sublevel, the correct filling order is to have one electron in each of the three 2p orbitals before pairing.
• The correct orbital diagram is the one where the 1s and 2s orbitals are filled with 2 electrons each (spin - paired), and the 2p orbitals have one electron in each of the three orbitals. So the correct diagram is the second one.
• Reason: Hund's rule states that electrons in degenerate orbitals (like the three 2p orbitals) will occupy the orbitals singly with parallel spins before pairing up to minimize electron - electron repulsion.

Answer:

Element	Preferred charge	Total number of electrons
Mg	+2	10
F	- 1	10
N	- 3	10
Li	+1	2

Sublevel	# of orbitals	Total # of electrons
p	3	6
d	5	10
f	7	14

a. The second orbital diagram is correct.
b. Because of Hund's rule, which states that electrons in degenerate orbitals occupy the orbitals singly with parallel spins before pairing up.