I read this background article the other day: However, when going across a period from left to right, the atomic radius actually tends to decrease. Why is this so? Each successive electron is going into the same principal energy level as the previous one, so the total amount of occupied space does not really go up significantly. Additionally, because protons are also added to the nucleus as you go across the row, the pull of the positively charged nucleus on the negatively charged electrons increases. This tighter pull leads to a slight decrease in atomic radius. As a result, the atomic radii of the elements exhibit a periodic trend, gradually tends to downward, but with a sharp spike up whenever electrons are added to a new principal energy level ( Figure below ). I am facing a new situation today: There are two elements, Zaxon and Barton. Zaxon is an element that is further left on the period, and Barton is on the right of the period. Using the knowledge I acquired from the background article, how should I answer correctly the following question regarding my new situation: Which element has a weaker pull between the nucleus and the electron?
Zaxon