Question

q1 chemistry: u2l16 excited electrons
prepwork part 1: electron configuration practice
*remember: isoelectronic means the same # of electrons, which also means identical electron configuration!

1. **which ion is isoelectronic to mg+2?

a. ca+2 b. cl−1 c. na+1 d. s−2

1. **which pair has identical electron configurations?

a. s−2 and cl−1 b. s0 and ar0 c. k0 and na+1 d. cl−1 and k0

1. *how do you know?
2. *why might it be important to identify isoelectronic ions/atoms?

for each of the following atoms, write the full electron configuration.

1. selenium atom 2. selenium ion with a charge of +4
2. fluorine atom 4. fluoride ion with a charge of - 1
3. silver atom 6. silver ion with a charge of +1

Explanation:

Step1: Determine electrons in Mg²⁺

Magnesium (Mg) has atomic number 12. Mg²⁺ has 12 - 2=10 electrons.

Step2: Analyze each option

• a. Ca²⁺: Calcium (Ca) has atomic number 20. Ca²⁺ has 20 - 2 = 18 electrons.
• b. Cl⁻: Chlorine (Cl) has atomic number 17. Cl⁻ has 17+1 = 18 electrons.
• c. Na⁺: Sodium (Na) has atomic number 11. Na⁺ has 11 - 1=10 electrons.
• d. S²⁻: Sulfur (S) has atomic number 16. S²⁻ has 16 + 2=18 electrons.

Step3: For question 2

• a. S²⁻ has 16+2 = 18 electrons and Cl⁻ has 17 + 1=18 electrons. They are isoelectronic.
• b. S has 16 electrons and Ar has 18 electrons, not isoelectronic.
• c. K has 19 electrons and Na⁺ has 10 electrons, not isoelectronic.
• d. Cl⁻ has 18 electrons and K has 19 electrons, not isoelectronic.

Step4: Answer to question 3

We know by calculating the number of electrons in each atom/ion. Atoms/ions with the same number of electrons are isoelectronic and have identical electron - configurations.

Step5: Answer to question 4

Identifying isoelectronic ions/atoms is important because they often have similar chemical and physical properties due to having the same electron - shell structure.

Step6: Electron configurations

Selenium atom (Se, atomic number 34)

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴

Selenium ion with a charge of +4 (Se⁴⁺)

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰

Fluorine atom (F, atomic number 9)

1s²2s²2p⁵

Fluoride ion with a charge of - 1 (F⁻)

1s²2s²2p⁶

Silver atom (Ag, atomic number 47)

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s¹4d¹⁰

Silver ion with a charge of +1 (Ag⁺)

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶4d¹⁰

Answer:

1. c. Na⁺
2. a. S⁻² and Cl⁻¹
3. By calculating the number of electrons in each atom/ion. Atoms/ions with the same number of electrons are isoelectronic and have identical electron - configurations.
4. They often have similar chemical and physical properties due to having the same electron - shell structure.
5. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴
6. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰
7. 1s²2s²2p⁵
8. 1s²2s²2p⁶
9. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s¹4d¹⁰
10. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶4d¹⁰