write out electron configurations for each of the following. only use your periodic table and your knowledge of the three rules to complete this task.
1. si
4. ne
2. k⁺
5. co
3. na

Question

Accepted Answer

### 1. Si (Silicon)
# Explanation:
## Step1: Determine atomic number
Si has atomic number 14, so 14 electrons.
## Step2: Apply Aufbau principle
Fill orbitals in order: $1s$, $2s$, $2p$, $3s$, $3p$.
$1s^2$ (2 e⁻), $2s^2$ (2 e⁻, total 4), $2p^6$ (6 e⁻, total 10), $3s^2$ (2 e⁻, total 12), $3p^2$ (2 e⁻, total 14).
# Answer: $1s^2 2s^2 2p^6 3s^2 3p^2$

### 2. $K^+$ (Potassium ion)
# Explanation:
## Step1: Atomic number of K
K (atomic number 19) loses 1 e⁻ to form $K^+$, so 18 electrons.
## Step2: Aufbau principle for 18 e⁻
Fill $1s^2$, $2s^2$, $2p^6$, $3s^2$, $3p^6$ (matches Ar’s configuration).
# Answer: $1s^2 2s^2 2p^6 3s^2 3p^6$

### 3. Na (Sodium)
# Explanation:
## Step1: Atomic number of Na
Na has atomic number 11, 11 electrons.
## Step2: Aufbau principle
$1s^2$ (2), $2s^2$ (2, total 4), $2p^6$ (6, total 10), $3s^1$ (1, total 11).
# Answer: $1s^2 2s^2 2p^6 3s^1$

### 4. Ne (Neon)
# Explanation:
## Step1: Atomic number of Ne
Ne has atomic number 10, 10 electrons.
## Step2: Aufbau principle
$1s^2$ (2), $2s^2$ (2, total 4), $2p^6$ (6, total 10).
# Answer: $1s^2 2s^2 2p^6$

### 5. Co (Cobalt)
# Explanation:
## Step1: Atomic number of Co
Co has atomic number 27, 27 electrons.
## Step2: Aufbau principle (note: $3d$ fills after $4s$ but before $4p$)
$1s^2$ (2), $2s^2$ (2, 4), $2p^6$ (6, 10), $3s^2$ (2, 12), $3p^6$ (6, 18), $4s^2$ (2, 20), $3d^7$ (7, total 27).
# Answer: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^7$ (or $ [Ar] 4s^2 3d^7 $)

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QUESTION IMAGE

Question

Explanation:

1. Si (Silicon)

Step1: Determine atomic number

Step2: Apply Aufbau principle

Step1: Atomic number of K

Step2: Aufbau principle for 18 e⁻

Step1: Atomic number of Na

Step2: Aufbau principle

Answer:

2. \(K^+\) (Potassium ion)