If the atomic number of an elements is 13, it will be placed in the periodic table in

Options

A. Group 1
B. Group 3
C. Group 13
D. Group 11

Answer

To determine where an element with an atomic number of 13 is placed in the periodic table, we can follow these steps:

### Step 1: Determine the Electronic Configuration
The atomic number of an element indicates the number of protons and, in a neutral atom, the number of electrons. For an atomic number of 13, the electronic configuration can be determined using the Aufbau principle, which states that electrons fill orbitals starting from the lowest energy level to the highest.

- **1s²**: 2 electrons
- **2s²**: 2 electrons
- **2p⁶**: 6 electrons
- **3s²**: 2 electrons
- **3p¹**: 1 electron

So, the electronic configuration of the element with atomic number 13 is:
**1s² 2s² 2p⁶ 3s² 3p¹**.

### Step 2: Identify the Valence Shell
The valence shell is the outermost shell of an atom that contains electrons. In this case, the highest principal quantum number (n) is 3, which means the valence shell is the 3rd shell.

### Step 3: Count the Valence Electrons
To find the group number, we need to determine how many valence electrons are present in the outermost shell (n=3).

From the electronic configuration:
- **3s²** contributes 2 electrons.
- **3p¹** contributes 1 electron.

Thus, the total number of valence electrons = 2 + 1 = **3 valence electrons**.

### Step 4: Determine the Group Number
In the periodic table, elements in the p-block have their group number calculated by adding 10 to the number of valence electrons.

So, for this element:
- Valence electrons = 3
- Group number = 3 + 10 = **13**.

### Step 5: Identify the Period and Block
- The element with atomic number 13 is in the **3rd period** (since n=3).
- Since the last electron is in the p-orbital (3p¹), this element belongs to the **p-block** of the periodic table.

### Conclusion
The element with atomic number 13 is placed in the **3rd period** and **group 13** of the periodic table.

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