For each element, indicate the number of valence electrons, core electrons, and unpaired electrons in the ground state: (a) sodium.

Video transcript

hey everyone in this example, we need to determine which of the given statements is true for a calcium atom. So before we analyze our statements below, we're going to write out the configuration for calcium. And so we're going to begin by recognizing that calcium is located across period four in group To a of our periodic table. And it has an atomic number which is represented by the symbol z equal to 20. Now to begin its atomic or electron configuration because we recognize that it's in period four. We want to begin with the shorthand configuration where we'll find the noble gas that comes at period three and that's going to correspond to our noble gas being argon. And so moving into the fourth energy level where period four begins, we would count for two units in our S sub level to get to our atom calcium meaning that we fill in two electrons in our S sublevel which can only hold a maximum of two electrons because it has one orbital. Our next step is to also recognize now that we have our configuration that we have a certain number of core electrons. And we would find that By 1st Identifying Our Valence Electrons. Let's recall that our valence electrons, our our outermost electrons. And so that would be the electrons in the for us to sub level which consists of our violence orbital. So we have two valence electrons here when we add up that exponents, which is just a two here. And so everything before that would be our core orbital which consists of just argon. And so we would just refer to the atomic number of argon And we would see that Argon has an atomic number equal to 18. So we would therefore have 18 electrons in our core orbital. And as we stated, our s orbital only has a total of one orbital. So we'll just represent that orbital here by this underline. And we should recall that because we have this exponents to to get to our adam calcium, we fully filled in this orbital which can hold a maximum of two electrons. So we would fill it in with the poly exclusion principle where we have one electron represented by a downward arrow and the second represented by an upward arrow. So we have zero unfilled orbital's because all of our orbital's are filled in. And so that would mean that our final answer to complete this example would be choice C, which states that calcium has a total of two valence electrons which we definitely agree with 18 core electrons which we determined comes from its configuration of argon and then zero on paired electrons, which we definitely agree with because we have all 18 electrons filled in for argon and then zero unfilled orbital's resulting from our s orbital also being fully filled in with its two electrons here. So C is the final answer. If you have any questions, please leave them down below. And I will see everyone in the next practice video