1. Electronic Configuration:
* Bromine (Br) has an atomic number of 35, meaning it has 35 protons and 35 electrons.
* Its electronic configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵
2. Core Electrons vs. Valence Electrons:
* Core electrons are the inner electrons that are not involved in chemical bonding. They are found in the filled inner shells.
* Valence electrons are the outermost electrons that are involved in chemical bonding. They are found in the partially filled outermost shell.
3. Identifying Core Electrons:
* Looking at the electronic configuration, we can identify the core electrons as those in the first three shells (1s², 2s², 2p⁶, 3s², 3p⁶).
* The electrons in the 4s² and 4p⁵ are the valence electrons.
4. Total Core Electrons:
* Add the number of electrons in the core shells: 2 + 2 + 6 + 2 + 6 = 18 core electrons
Therefore, bromine has 18 core electrons.
