How many electrons are present in an atom in which the first and ...

Question

How many electrons are present in an atom in which the first and second shells and the 3s subshell are filled? Name the element.

Accepted Answer

Welcome back everyone. The 1st, 2nd and 3rd shells and the four s sub shell of an atom are filled. How many electrons are present in the atom? And what is the identity of the element? So we have an atom with a configuration filled up to the four s sub shell. So our shell number, or the energy level where our electrons lie at the outermost level is the fourth energy level. Then we have our sub shell which is the S. Sub shell and then our electrons filled in this sub shell. We should recall for the S sub shell specifically hold a maximum of two electrons were also told that the 1st, 2nd and 3rd shells are going to be filled. And so we can include that in our arrangement here where we're going to move this below. We begin with shell number one for the first energy level. The sub shell for the first energy level of atoms on our periodic table will always just be the S sub shell which also again holds a maximum of two electrons only having one orbital. And we can actually showcase the orbital as a box filling in our two electrons as arrows with opposite spins. So let's do that instead and right, two electrons above. So now moving on to the second level, recall that on our periodic table. Our second level shell number consists of the S sub shell as well as the P sub shell. So we have our one orbital for R. S sub shell which again holds two electrons with opposite spins filled inside. And then R P sub shell recall consists of three orbital's total in which we have a total of six maximum electrons of opposite spins filled in each orbital now moving on to the third energy level. We would likewise as shell number two have the S and P sub shell, but also recognize and recall that our D block on our periodic table, which contains our transition metals, would also be the sub shell included, which even though it's across period four on our periodic table, the D block begins at the third energy level. And so what we have is again our single orbital for R. S. Sub shell which has two electrons. We have our three electrons or sorry, six electrons in our p orbital. And then recall that our D block consists of five orbital's total In which we can only hold a maximum of 10 electrons also filled in with opposite spins, just like our S&P block. And let's add the label for the fourth energy level with two electrons. So now with our number of electrons outlined for each of our orbital's in each sub shell we're going to need to take the sum of electrons. And so we would find that are some of electrons is found from taking the sum of electrons fulfilled in each orbital. So as we stated for our one s orbital, we counted a total of two electrons for we're adding onto this hour to us and two p orbital orbital's in which we counted a total of And rather let's write this separately. So for two s we're going to put a parentheses and we counted two electrons total plus our two p orbital in which we counted a total of six electrons. Then adding on to this, we have our three s orbital in which we counted two electrons plus our three p orbital filled in with six electrons and then plus our three D orbital filled in with 10 electrons continuing the sun below. We have plus our four s orbital finally filled in with the two electrons that we counted and so taking the sum of electrons, we just want to again add our number of electrons in each parentheses that I've written. And this is going to equal a sum of 30 electrons total. And so on our periodic table, we're going to see that the atomic number represented by the symbol Z. So we'll say Z equal to 30 therefore means that we have the atom or element sink represented by this symbol ZN on our periodic table. Again under the atomic number 30. And so for our final answer, we've successfully identified the total number of electrons present in this atom as electrons. And we've also successfully identified the identity of our atom as zinc. So what's highlighted in yellow corresponds to our final answer which matches choice a as the correct answer to complete this example. So I hope this made sense. and let us know if you have any questions.

How many electrons are present in an atom in which the first and second shells and the 3s subshell are filled? Name the element.

Key Concepts

Electron Shells and Subshells

Electron Configuration

Identifying Elements by Electron Count

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