How many dots are shown in the electron dot diagram for calcium, in group II and period 4 with 20 protons and 20 electrons?

Question

matt101 · Answer

In electron dot diagrams, each dot represents a valence electron (an electron in the outer shell of the atom). Up until calcium, there are a maximum of 2 electrons in the first shell, 8 electrons in the second shell, and 8 electrons in the third shell. Adding these up, we only have 18 electrons, but calcium has 20. This means the last 2 electrons begin to fill the fourth shell.

So...for the electron dot diagram for calcium, there are 2 dots shown.