electron configuration practice worksheet
in the space below, write the full (unabbreviated) electron configurations of the following elements:
1) sodium
2) iron
3) bromine
4) barium
5) neptunium
in the space below, write the noble gas (abbreviated) electron configurations of the following elements:
6) cobalt
7) silver
8) tellurium
9) radium
10) lawrencium
determine what elements are denoted by the following electron configurations:
11) $1s^{2}2s^{2}2p^{6}3s^{2}3p^{4}$
12) $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{1}$
13) $kr5s^{2}4d^{10}5p^{3}$
14) $xe6s^{2}4f^{14}5d^{6}$
15) $rn7s^{2}5f^{11}$
determine which of the following electron configurations are not valid: state which rule has been violated.
16) $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}4d^{10}4p^{5}$
17) $1s^{2}2s^{2}2p^{6}3s^{3}3d^{5}$
18) $ra7s^{2}5f^{8}$
19) $kr5s^{2}4d^{10}5p^{5}$
20) $xe$

Question

Accepted Answer

### Problem 1: Full Electron Configuration of Sodium
# Explanation:
## Step1: Determine atomic number of Na
Sodium (Na) has atomic number 11, so 11 electrons.
## Step2: Fill orbitals by Aufbau principle
Orbitals fill as $1s \to 2s \to 2p \to 3s \to \dots$.
- $1s^2$ (2 electrons), $2s^2$ (2, total 4), $2p^6$ (6, total 10), $3s^1$ (1, total 11).

# Answer:
$1s^2 2s^2 2p^6 3s^1$

### Problem 2: Full Electron Configuration of Iron
# Explanation:
## Step1: Atomic number of Fe
Iron (Fe) has atomic number 26, 26 electrons.
## Step2: Apply Aufbau principle
Fill $1s^2$ (2), $2s^2$ (4), $2p^6$ (10), $3s^2$ (12), $3p^6$ (18), $4s^2$ (20), then $3d^6$ (26).

# Answer:
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6$

### Problem 3: Full Electron Configuration of Bromine
# Explanation:
## Step1: Atomic number of Br
Bromine (Br) has atomic number 35, 35 electrons.
## Step2: Fill orbitals
$1s^2$ (2), $2s^2$ (4), $2p^6$ (10), $3s^2$ (12), $3p^6$ (18), $4s^2$ (20), $3d^{10}$ (30), $4p^5$ (35).

# Answer:
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^5$

### Problem 4: Full Electron Configuration of Barium
# Explanation:
## Step1: Atomic number of Ba
Barium (Ba) has atomic number 56, 56 electrons.
## Step2: Fill orbitals
$1s^2$ (2), $2s^2$ (4), $2p^6$ (10), $3s^2$ (12), $3p^6$ (18), $4s^2$ (20), $3d^{10}$ (30), $4p^6$ (36), $5s^2$ (38), $4d^{10}$ (48), $5p^6$ (54), $6s^2$ (56).

# Answer:
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2$

### Problem 5: Full Electron Configuration of Neptunium
# Explanation:
## Step1: Atomic number of Np
Neptunium (Np) has atomic number 93, 93 electrons.
## Step2: Fill orbitals (including f-orbitals)
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^6 7s^2 5f^5$ (sum electrons: 2+2+6+2+6+2+10+6+2+10+6+2+14+10+6+2+5 = 93).

# Answer:
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^2 4d^{10} 5p^6 6s^2 4f^{14} 5d^{10} 6p^6 7s^2 5f^5$

### Problem 6: Noble Gas Configuration of Cobalt
# Explanation:
## Step1: Noble gas before Co
Cobalt (Co, Z=27) comes after Argon (Ar, Z=18).
## Step2: Remaining electrons
27 - 18 = 9. Fill $4s^2$ then $3d^7$ (but noble gas config uses [Ar] + valence: [Ar] $4s^2 3d^7$).

# Answer:
$[\text{Ar}] 4s^2 3d^7$

### Problem 7: Noble Gas Configuration of Silver
# Explanation:
## Step1: Noble gas before Ag
Silver (Ag, Z=47) comes after Krypton (Kr, Z=36).
## Step2: Remaining electrons
47 - 36 = 11. But $4d^{10} 5s^1$ (due to d-orbital stability), so [Kr] $4d^{10} 5s^1$.

# Answer:
$[\text{Kr}] 4d^{10} 5s^1$

### Problem 8: Noble Gas Configuration of Tellurium
# Explanation:
## Step1: Noble gas before Te
Tellurium (Te, Z=52) comes after Krypton (Kr, Z=36).
## Step2: Remaining electrons
52 - 36 = 16. Fill $5s^2 4d^{10} 5p^4$, so [Kr] $5s^2 4d^{10} 5p^4$.

# Answer:
$[\text{Kr}] 5s^2 4d^{10} 5p^4$

### Problem 9: Noble Gas Configuration of Radium
# Explanation:
## Step1: Noble gas before Ra
Radium (Ra, Z=88) comes after Radon (Rn, Z=86).
## Step2: Remaining electrons
88 - 86 = 2, so [Rn] $7s^2$.

# Answer:
$[\text{Rn}] 7s^2$

### Problem 10: Noble Gas Configuration of Lawrencium
# Explanation:
## Step1: Noble gas before Lr
Lawrencium (Lr, Z=103) comes after Radon (Rn, Z=86).
## Step2: Remaining electrons
103 - 86 = 17. Fill $7s^2 5f^{14} 6d^1$, so [Rn] $7s^2 5f^{14} 6d^1$.

# Answer:
$[\text{Rn}] 7s^2 5f^{14} 6d^1$

### Problem 11: Element from $1s^2 2s^2 2p^6 3s^2 3p^4$
# Explanation:
## Step1: Count electrons
Sum: 2+2+6+2+4 = 16.
## Step2: Atomic number 16 is sulfur (S).

# Answer:
Sulfur (S)

### Problem 12: Element from $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^6 5s^1$
# Explanation:
## Step1: Count electrons
Sum: 2+2+6+2+6+2+10+6+1 = 37.
## Step2: Atomic number 37 is rubidium (Rb).

# Answer:
Rubidium (Rb)

### Problem 13: Element from $[\text{Kr}] 5s^2 4d^{10} 5p^3$
# Explanation:
## Step1: Kr has Z=36, add remaining electrons
36 + 2 + 10 + 3 = 51.
## Step2: Atomic number 51 is antimony (Sb).

# Answer:
Antimony (Sb)

### Problem 14: Element from $[\text{Xe}] 6s^2 4f^4 5d^6$
# Explanation:
## Step1: Xe has Z=54, add remaining electrons
54 + 2 + 4 + 6 = 66.
## Step2: Atomic number 66 is dysprosium (Dy).

# Answer:
Dysprosium (Dy)

### Problem 15: Element from $[\text{Rn}] 7s^2 5f^{11}$
# Explanation:
## Step1: Rn has Z=86, add remaining electrons
86 + 2 + 11 = 99.
## Step2: Atomic number 99 is einsteinium (Es).

# Answer:
Einsteinium (Es)

### Problem 16: Invalid Electron Configuration ($1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4d^{10} 4p^5$)
# Explanation:
## Step1: Check orbital order
After $4s$, $3d$ should fill before $4d$ (Aufbau principle: $3d$ < $4d$ in energy). Here $4d$ is filled before $3d$, violating Aufbau.

# Answer:
Invalid, violates Aufbau Principle (skips $3d$ orbital).

### Problem 17: Invalid Electron Configuration ($1s^2 2s^2 2p^6 3s^3 3d^5$)
# Explanation:
## Step1: Check $3s$ orbital capacity
$s$-orbitals hold max 2 electrons. $3s^3$ has 3 electrons, violating Pauli Exclusion Principle.

# Answer:
Invalid, violates Pauli Exclusion Principle ($3s$ holds >2 electrons).

### Problem 18: Invalid Electron Configuration ($[\text{Ra}] 7s^2 5f^8$)
# Explanation:
## Step1: Check noble gas abbreviation
Radium (Ra) is not a noble gas (noble gases: He, Ne, Ar, Kr, Xe, Rn). Abbreviated config must use noble gas, so using Ra (non-noble) is invalid.

# Answer:
Invalid, noble gas abbreviation must use a noble gas (Ra is not a noble gas).

### Problem 19: Valid Electron Configuration ($[\text{Kr}] 5s^2 4d^{10} 5p^5$)
# Explanation:
## Step1: Count electrons
Kr (36) + 2 + 10 + 5 = 53. Atomic number 53 is iodine (I), config follows Aufbau (5s, 4d, 5p in order).

# Answer:
Valid (Iodine, I)

### Problem 20: Element from $[\text{Xe}]$
# Explanation:
## Step1: Xe has atomic number 54.
## Step2: So the element is xenon (Xe).

# Answer:
Xenon (Xe)

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QUESTION IMAGE

Question

Explanation:

Problem 1: Full Electron Configuration of Sodium

Step1: Determine atomic number of Na

Step2: Fill orbitals by Aufbau principle

Step1: Atomic number of Fe

Step2: Apply Aufbau principle

Step1: Atomic number of Br

Step2: Fill orbitals

Answer:

Problem 2: Full Electron Configuration of Iron