Questions: Write the full and abbreviated electron configurations for bromine. How many core and valance electrons does it have?

Solution Steps

Bromine (Br) has an atomic number of 35, which means it has 35 electrons.

To write the full electron configuration, we fill the electron orbitals in the order of increasing energy levels:

1. \(1s^2\)
2. \(2s^2\)
3. \(2p^6\)
4. \(3s^2\)
5. \(3p^6\)
6. \(4s^2\)
7. \(3d^{10}\)
8. \(4p^5\)

Thus, the full electron configuration for bromine is: \[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \, 3d^{10} \, 4p^5 \]

The abbreviated electron configuration uses the nearest noble gas with a lower atomic number as a reference. For bromine, the nearest noble gas is argon (Ar), which has an electron configuration of \(1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6\).

Thus, the abbreviated electron configuration for bromine is: \[ [\text{Ar}] \, 4s^2 \, 3d^{10} \, 4p^5 \]

• Core Electrons: These are the electrons in the inner shells. For bromine, the core electrons are those in the configuration of argon, which is 18 electrons.
• Valence Electrons: These are the electrons in the outermost shell. For bromine, the valence electrons are in the \(4s\) and \(4p\) orbitals, totaling 7 electrons.

Final Answer