To determine the valencies of the elements V, W, X, Y, and Z, we will follow these steps:
### Step 1: Identify the atomic numbers and elements
The elements are given as:
- V: \( _{15}^{31}V \) (Atomic number = 15)
- W: \( _{9}^{19}W \) (Atomic number = 9)
- X: \( _{3}^{7}X \) (Atomic number = 3)
- Y: \( _{18}^{40}Y \) (Atomic number = 18)
- Z: \( _{12}^{24}Z \) (Atomic number = 12)
### Step 2: Write the electronic configurations
We will write the electronic configurations based on the atomic numbers:
- V (15): \( 2, 8, 5 \)
- W (9): \( 2, 7 \)
- X (3): \( 2, 1 \)
- Y (18): \( 2, 8, 8 \)
- Z (12): \( 2, 8, 2 \)
### Step 3: Determine the number of valence electrons
The valence electrons are the electrons in the outermost shell:
- V: 5 valence electrons
- W: 7 valence electrons
- X: 1 valence electron
- Y: 8 valence electrons
- Z: 2 valence electrons
### Step 4: Calculate the valency
The valency can be determined based on the number of valence electrons:
- If the number of valence electrons is greater than 4, the valency is calculated as \( 8 - \text{(number of valence electrons)} \).
- If the number of valence electrons is less than or equal to 4, the valency is equal to the number of valence electrons.
Now, let's calculate the valency for each element:
- **V (5 valence electrons)**: \( 8 - 5 = 3 \) → Valency = 3
- **W (7 valence electrons)**: \( 8 - 7 = 1 \) → Valency = 1
- **X (1 valence electron)**: Valency = 1 (since it's less than 4)
- **Y (8 valence electrons)**: Valency = 0 (since it's a noble gas)
- **Z (2 valence electrons)**: Valency = 2 (since it's less than 4)
### Step 5: Summarize the valencies
- Valency of V = 3
- Valency of W = 1
- Valency of X = 1
- Valency of Y = 0
- Valency of Z = 2
### Final Answer:
The valencies of elements V, W, X, Y, and Z are respectively: **3, 1, 1, 0, 2**.
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