How many inner shell electrons does an element in period 3 of the periodic table have?

• A. 10
• B. 18
• C. 8
• D. 2

Answer: (A)

Verified step by step guidance

1. Identify the element's period in the periodic table, which is period 3. This means the element's electrons fill up to the third energy level (shell).
2. Recall that inner shell electrons are those electrons that are not in the outermost (valence) shell. For period 3 elements, the outermost shell is the third shell.
3. Determine the total number of electrons in the inner shells, which are the electrons in shells 1 and 2.
4. Remember that the first shell (n=1) can hold up to 2 electrons, and the second shell (n=2) can hold up to 8 electrons, so the total inner shell electrons for any period 3 element is the sum of these two shells: 2 + 8.
5. Conclude that the number of inner shell electrons for any element in period 3 is 10, since the first two shells are completely filled before electrons start filling the third shell.