Let's determine the electron configuration for bromine (Br), which has an atomic number of 35. The atomic number indicates the number of electrons in a neutral atom.
We will fill the electron orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle.
1. Understand the order of orbital filling: Electrons are distributed among the orbitals in order of increasing energy levels. The order is as follows:
- 1s
- 2s
- 2p
- 3s
- 3p
- 4s
- 3d
- 4p
- and so on.
2. Assign electrons to orbitals:
- 1s: 2 electrons
- 2s: 2 electrons
- 2p: 6 electrons
- 3s: 2 electrons
- 3p: 6 electrons
- 4s: 2 electrons
- 3d: 10 electrons
- 4p: 5 electrons
Now let's add the electrons step-by-step:
- 1s²: 2 electrons (total 2)
- 2s²: 2 electrons (total 4)
- 2p⁶: 6 electrons (total 10)
- 3s²: 2 electrons (total 12)
- 3p⁶: 6 electrons (total 18)
- 4s²: 2 electrons (total 20)
- 3d¹⁰: 10 electrons (total 30)
- 4p⁵: 5 electrons (total 35)
Putting all these together, the electron configuration for bromine is:
[tex]\[ \text{Br}: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^5 \][/tex]
Comparing this with the given options:
1. [tex]\( 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^{10} 4 p^5 \)[/tex]
2. [tex]\( 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^{10} 4 p^6 \)[/tex]
3. [tex]\( 1 s^2 2 s^2 2 p^6 3 s^2 3 p^4 4 s^2 3 d^{10} 4 p^5 \)[/tex]
4. [tex]\( 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^9 4 p^5 \)[/tex]
The correct electron configuration for bromine corresponds to the first option:
[tex]\[ 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^5 \][/tex]
So the correct answer is option 1.
