Why does the fourth period in the periodic table contain 18 elements?

Question

Accepted Answer

Welcome back everyone. How many elements are there in the sixth period of the periodic table. And provide your reasoning. Looking at our answer choices. We can see that some of our options describe the orbital's involved up to the sixth period of our periodic table and we can correlate this to our number of electrons and number of elements. So let's begin by thinking of our first sub shell Within our 6th period of our periodic table. And recall that our period numbers are the rows across our periodic table. So it would just be one row for the 6th period, it would be the 6th row. And so let's look at the first sub shell which would be our six S sub shell. Recall that our S sub shell consists of just one single orbital, which can hold a maximum of two electrons. And so right now we can have a count of two electrons for r six s sub shell across the sixth period of our periodic table. Now moving forward across our sixth period, we would hit the sub shell next lowest in energy, which would be our four F sub shell, Which we can see has atoms that have atomic numbers ranging between 57 through 70. So let's note that down. See values through 70. And recall that Z represents our symbol for atomic number for the six S sub shell. We can say that our Z values cover between numbers 55 through 56 representing two atoms. Now going back to our four F sub shell, recall that this sub shell consists of a total of seven orbital's which I'm representing as boxes And can hold a maximum of 14 electrons which we represent in our boxes or in our orbital's as arrows with opposite spins paired up. So this would make a total of 14 electrons. So let's keep going and consider our next sub shell, which would be our five D sub shell across our sixth period. And recognize that on our periodic table are five D Sub shell covers atomic numbers or R Z values of through 80. And recall that R D sub shell consists of a total of five orbital's Which can hold a maximum of electrons. And next moving across our 6th period, we would hit our six p block which covers atomic numbers Through 86. Recall that in our P block we have a total of three orbital's which can hold a maximum of six electrons. So now based on our answer choices, we need to add up our electrons to determine our number of elements and so are some of electrons would equal six plus 10 plus 14 plus two. And that's going to leave us with a total of 32 electrons total, Meaning that therefore the 6th period On our product table contains 32 elements. And so we would confirm that the correct answer to complete this example is going to be choice. It looks like choice B since choice D almost looks like it's correct. Except it mentions that we have the five F orbital, which we know that for our sixth period, the F block begins at the fourth energy level, which is correct. So we would rule out choices. D c n A B is our final answer. I hope that this made sense and let us know if you have any questions.

Why does the fourth period in the periodic table contain 18 elements?

Verified video answer for a similar problem:

Key Concepts

Periodic Table Structure

Electron Configuration

Transition Metals