How many core electrons does an atom of beryllium (Be) contain?

• A. 2
• B. 0
• C. 4
• D. 6

Answer: (A)

Verified step by step guidance

1. Identify the atomic number of beryllium (Be), which tells you the total number of electrons in a neutral atom. Beryllium has an atomic number of 4, so it has 4 electrons in total.
2. Recall that electrons are arranged in shells or energy levels around the nucleus. The first shell (closest to the nucleus) can hold up to 2 electrons, and the second shell can hold up to 8 electrons.
3. Determine the electron configuration of beryllium. The electrons fill the lowest energy levels first, so the configuration is 1s\^2 2s\^2.
4. Core electrons are those in the inner shells, not involved in bonding, while valence electrons are in the outermost shell. For beryllium, the 1s\^2 electrons are core electrons, and the 2s\^2 electrons are valence electrons.
5. Count the number of core electrons by looking at the electrons in the inner shell(s). For beryllium, this is the 2 electrons in the 1s orbital.