Question
What do all of the elements in a given horizontal row of the Periodic Table have in common? a They have the same number of electrons. b They have the same total number of occupied sublevels. C They have the same chemical reactivity. d They have the same number of occupied principal energy levels.
Answer
4
(378 Votes)
May
Master · Tutor for 5 years
Answer
d
Explanation
In the Periodic Table, the horizontal rows are called periods. As you move across a period from left to right, the atomic number of the elements increases, which means that each subsequent element has one more proton and one more electron than the previous one. The key feature that elements in the same period share is that they have the same number of occupied principal energy levels. For example, all elements in the second period have their electrons filling the second energy level. The number of electrons is not the same across a period, as it increases from left to right. Chemical reactivity varies across a period, often showing a trend from metals to nonmetals. The total number of occupied sublevels increases across a period as well, as electrons fill available sublevels in the same principal energy level.