State the number of valence electrons, bonding pairs, and lone pa...

Question

State the number of valence electrons, bonding pairs, and lone pairs in each of the following Lewis structures: (6.6) c.

Lewis structure of phosphine (PH3) showing bonding and lone pairs.

Accepted Answer

Welcome back everyone. Phosphine is a highly flammable gas used in semiconductor industries. We need to determine the number of advanced electrons lone pairs and bonding pairs in phosphene based on its lower structure given below. Now, let's begin by defining the fact that the term bonding pairs refers to electrons in a bond. And we're going to recall that a single bond is made up of two electrons. So two electrons in a single fond, whereas lone pairs, we should recall refer to loan electrons that are not formed in a bond and valence electrons we should recall are outer shell electrons of an atom. So let's begin by calculating the total valence electrons in our structure of phosphine in which based on this les structure, we can observe, we have a single central phosphorus atom bonded to three hydrogen atoms. And therefore, our chemical formula is P H sub three. So we're calculating the total valence electrons for P H three or our chemical formula for phosphine. And we're going to need to begin with our atom phosphorus in which we should recall that on our periodic table, phosphorus is located in group five. A recall that group number corresponds to valence electrons or outer shell electrons. So this will mean that our phosphorus atom has a total of five valence electrons that it contributes within the structure. Next, we have our atom hydrogen, which we should recall is located in group one a on our periodic table corresponding to one valence electron. Now note that in our chemical formula and within our structure, we can see that the subscript of three corresponds to the three hydrogen atoms within our molecule of phosphene. So we're going to take our one valance electron for one atom of hydrogen and multiply by three atoms of hydrogen. And this will yield a contribution of three valence electrons. Now taking the total of vals electrons, we would have five plus three and that's going to give us eight vals electrons total for our structure. This is going to be our first answer so far. And now we need to just determine our number of lone pairs and bonding pairs. As we stated earlier, lone pairs are defined as electrons specifically just a total of two in a pair that are not formed within a bond. So they would just exist as two dots paired next to one another beside an atom. And within our structure of phosphine, given we can observe that we actually have two dots as electrons which are not represented as a bond between our phosphorus and another atom, they're just at the top of phosphorus where there's no other atom sandwiched on the other side of these lone electrons. And so this would be considered as our lone pair. And this therefore means that we have one lone pair within our structure. So one lone pair in phosphine, this is going to be our second answer. And next, we have our bonding pairs to determine where as we defined earlier, bonding pairs represent electrons that are within a bond. And recall that within a single bond, we have a total of two electrons where we can observe that within our structure between our central phosphorus and our terminal hydrogen atoms, we have lone electrons sandwiched between again, our central phosphorus and our terminal hydrogens. So when lone electrons are sandwiched between two other atoms, those two atoms are covalent bonded to one another, specifically, if they're both nonmetals, and so the electrons are being shared between those two atoms. And therefore, we can observe that we have a total of one bonding pair, two bonding pairs and three bonding pairs making up the three covalent bonds between our central phosphorus and our three terminal hydrogens. So our third final answer is going to be that we have three bonding pairs in phosphine. And within these three bonds, we've used up a total of 246 of our eight valence electrons, which is why the remaining two of our eight total are used as a lone pair on phosphorus. So that our phosphorus being a period two element can honor the octet rule and have a total of eight valence electrons around itself within the structure. Now, our third final answer is again, three bonding pairs and phosphine. And in summary, we've determined our three final answers where our number of boun electrons is eight. For phosphine, we have one loan pair and we have three bonding pairs. So I hope that this made sense and let us know if you have any questions.

State the number of valence electrons, bonding pairs, and lone pairs in each of the following Lewis structures: (6.6) c.

Key Concepts

Valence Electrons

Bonding Pairs

Lone Pairs

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