Why do the chemical properties cycle through each period?
every eighth element starting with hydrogen restarts the transition from metal to inert gas.
elements with atomic numbers which are multiples of eight start a new period.
the outermost shell of all atoms with two or more electron shells will not have more than 8 electrons.
each period represents a cycle of completing the outer electron shell.

Option (d) is the correct answer.

Explanation:

A period is represented by a horizontal line as we move from left to right in a periodic table.

Since, number of electrons keep on adding into the elements while we move in a period. Therefore, number of valence electrons also increases in a period and when the valence shell of last element of a period gets completely filled then the cycle repeats itself.

And elements with same number of valence electrons will show same chemical properties.

Thus, we can conclude that the chemical properties cycle through each period because each period represents a cycle of completing the outer electron shell.

the right answer is c i just did the question.