The properties of the elements such as atomic or ionic radii ionisation enthalpy, electron gain enthalpy and electronegativity are directly or indirectly related to their electronic configuration and are called periodic properties. A part the periodic table is given below :
`{:(C, N, O, F),(, P, S, Cl),(,,Se, Br), (,,,I):}`
Bromine belongs to period

Options

A. third
B. fourth
C. fifth
D. second

Answer

To determine the period to which bromine belongs, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Element**: We are asked about bromine (Br). Its atomic number is 35.

2. **Locate Bromine in the Periodic Table**: In the provided part of the periodic table, bromine is found in the fourth row (or period) along with other elements like chlorine (Cl) and iodine (I).

3. **Determine the Electronic Configuration**: The electronic configuration of bromine can be written as:
\[ \text{Br: } [\text{Ar}] 4s^2 3d^{10} 4p^5 \]
Here, [Ar] represents the electron configuration of argon, which is the noble gas preceding bromine.

4. **Identify the Valence Shell**: The valence shell is determined by the highest principal quantum number (n) in the electronic configuration. For bromine, the highest principal quantum number is 4 (from the 4s and 4p orbitals).

5. **Determine the Period**: The period number corresponds to the highest principal quantum number. Since the highest n for bromine is 4, it belongs to the **4th period** of the periodic table.

### Conclusion:
Bromine belongs to the **4th period** of the periodic table.

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