The group number, number of valence electrons, and valency of an element with atomic number 15, respectively, are :

Options

A. 16, 5 and 2
B. 16, 6 and 3
C. 15, 5 and 3
D. 15, 6 and 2

Explanation

To solve the question regarding the group number, number of valence electrons, and valency of the element with atomic number 15, we can follow these steps:

### Step 1: Identify the Element
The element with atomic number 15 is phosphorus (P).

### Step 2: Determine the Electronic Configuration
The electronic configuration of phosphorus can be written as:
- 1s² 2s² 2p⁶ 3s² 3p³
This configuration shows that phosphorus has a total of 15 electrons.

### Step 3: Identify the Valence Shell
The valence shell for phosphorus is the third shell (n=3), which includes the 3s and 3p orbitals:
- 3s² 3p³

### Step 4: Count the Valence Electrons
In the valence shell (3s² 3p³), phosphorus has:
- 2 electrons in the 3s orbital
- 3 electrons in the 3p orbital
Thus, the total number of valence electrons is:
- 2 + 3 = 5 valence electrons.

### Step 5: Determine the Group Number
For elements in the p-block, the group number can be calculated using the formula:
- Group number = 10 + number of valence electrons
Here, the number of valence electrons is 5, so:
- Group number = 10 + 5 = 15.

### Step 6: Determine the Valency
Valency is determined by how many electrons an atom needs to gain, lose, or share to achieve a full outer shell (octet). Phosphorus has 5 valence electrons and needs 3 more electrons to complete its octet (8 electrons total). Therefore, its valency is:
- Valency = 3 (since it can gain 3 electrons).

### Final Answer
Thus, for the element with atomic number 15 (phosphorus):
- Group number: 15
- Number of valence electrons: 5
- Valency: 3

### Summary
The group number, number of valence electrons, and valency of the element with atomic number 15 are:
- Group number: 15
- Valence electrons: 5
- Valency: 3

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