Which is the electron configuration for bromine?
A. $1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^{10} 4 p^5$
B. $1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^{10} 4 p^6$
C. $1 s^2 2 s^2 2 p^6 3 s^2 3 p^4 4 s^2 3 d^{10} 4 p^5$
D. $1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^9 4 p^5$
Answer (1)
Determine the number of electrons in a neutral bromine atom, which is equal to its atomic number (35).
Fill the orbitals in the correct order (1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p) until all 35 electrons are assigned.
The electron configuration for bromine is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 5 .
The correct electron configuration for bromine is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 5 .
Explanation
Problem Analysis and Setup We want to determine the electron configuration of bromine (Br). Bromine has an atomic number of 35, which means a neutral bromine atom has 35 electrons. We need to fill the electron orbitals in the correct order until we've placed all 35 electrons. The filling order is 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.
Filling the Orbitals Let's fill the orbitals:
1s can hold 2 electrons: 1 s 2
2s can hold 2 electrons: 1 s 2 2 s 2
2p can hold 6 electrons: 1 s 2 2 s 2 2 p 6
3s can hold 2 electrons: 1 s 2 2 s 2 2 p 6 3 s 2
3p can hold 6 electrons: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6
4s can hold 2 electrons: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2
3d can hold 10 electrons: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10
4p can hold up to 6 electrons, but we only need to add 5 to reach a total of 35: 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 5
So, the electron configuration for bromine is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 5 .
Final Answer Comparing our result with the given options, we find that the correct electron configuration for bromine is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 10 4 p 5 .
Examples
Understanding electron configurations is crucial in chemistry for predicting how elements will interact to form chemical bonds. For instance, knowing the electron configuration of bromine helps us understand its tendency to gain one electron to achieve a stable octet, leading to its reactivity as a halogen. This knowledge is applied in designing new materials, understanding chemical reactions, and developing new technologies in fields like pharmaceuticals and materials science. By understanding the arrangement of electrons, we can predict and control chemical behavior.
