What are the core and valence electrons in Calcium (Ca) and Magnesium (Mg)?

Calcium (Ca) has a total of 20 electrons, which are arranged in the following electronic configuration: 1s² 2s² 2p⁶ 3s². From this configuration, we can determine the number of core and valence electrons:

• Core Electrons: The core electrons are those that are not in the outermost shell. In the case of calcium, the electron configuration indicates that the first two shells (1s, 2s, 2p) contain 10 electrons, thus calcium has 10 core electrons.
• Valence Electrons: The valence electrons are the electrons in the outermost shell. For calcium, the outermost shell is the third shell, which contains 2 electrons (3s²). Therefore, calcium has 2 valence electrons.

Magnesium (Mg) has a total of 12 electrons, with the electronic configuration: 1s² 2s² 2p⁶ 3s². Analyzing this configuration gives us:

• Core Electrons: Similar to calcium, the 10 electrons in the inner shells (1s, 2s, 2p) are core electrons. Hence, magnesium also has 10 core electrons.
• Valence Electrons: The outermost shell for magnesium is the third shell, which also contains 2 electrons (3s²). Therefore, magnesium has 2 valence electrons.