How many covalent bonds are formed by each atom in the following molecules? Draw molecules using the electron-dot-symbols and lines to show the covalent bonds.
a. PH₃
b. H₂Se
c. HCl
d. SiF

Question

How many covalent bonds are formed by each atom in the following molecules? Draw molecules using the electron-dot-symbols and lines to show the covalent bonds.

a. PH₃

b. H₂Se

c. HCl

d. SiF

Accepted Answer

Welcome back everyone. Which of the following shows the correct number of covalent bonds formed by each atom as well as the electron dot symbols of the molecules with lines showing their covalent bonds. Let's begin by recalling what a covalent bond is. Recall that a covalent bond consists of an electron pair that is shared between two nonmetal atoms. Looking at example, one, we have arsenic trihydrate a sh sub three given in the prompt. And we're told that arsenic has three covalent bonds and each hydrogen has three covalent bonds. Now let's begin by calculating total valence electrons recall that arsenic is located in group five a on the periodic table corresponding to five valence electrons. Whereas hydrogen we recall is in group one, a corresponding to one val electron, we also have three atoms of hydrogen. So we want to multiply by three, giving a contribution of three electrons from hydrogen and just making more room here calculating the total val electrons, we would add five plus three which would give us eight vals electrons total for this structure. Now notice that in our structure, we have directly attached three valence electrons on arsenic. And as we stated arsenic should have five V electrons to be stable with a formal charge of zero because it only has three directly attached v electrons. We know that it's missing a lone pair in this, in this given electron dot symbol. So we know that this is not a correct electron dot symbol and also observe that as the third statement reads, it says that each hydrogen has three covalent bonds, we would not agree with that because although arsenic and hydrogen are both nonmetals based on their position on the periodic table, we can see that each hydrogen only has a single covalent bond to our central atom arsenic. So this should say one. However, they do have the correct statement for arsenic because it does have three covalent bonds to hydrogen being the central atom. So because we have two incorrect parts for part one, we can rule it out as an incorrect choice. Moving on to part two, we have electron dot symbol for hat which is our compound asinine hydride. We want to begin again by calculating total valance electrons starting with asinine recall that it is a group seven a atom on the periodic table corresponding to seven bound electrons. And hydrogen again will be giving a contribution of one val electron as determined before because again, it's a group, one a atom. So taking the total here, we have just eight bounces electrons total for this structure in the prompt that says that for part two asinine has one covalent bond based on its position in group seven A. We see that it is a definitely, we definitely going to be a non metal since it's in our halogen group and hydrogen, of course, we know is a non metal as well. So this is a covalent bond that we do observe being shared to the one hydrogen in this compound. We can observe that as a true statement. And then it says that hydrogen also has one covalent bond. Again, hydrogen just has one electron pair shared in this line here, which is our bond to asinine. So this is also a correct statement and notice that as we stated, Asinine should have seven valance electrons. So we can see directly attached to one electron in the co Bonta hydrogen on Asinine. And then it has three lon pairs. So that would give a total of seven V electrons for Aine. So we know that we have the correct electron dot symbol. And so choice two would be a correct choice because we also have accurate number of covalent bonds for each atom moving on to choice three. It says that we need the electron dot symbol for H sub two te which is hydrogen telluride. I'm sorry. This is underlined here. So we need to calculate total valence electrons. Beginning with telo recall that on our product table telo is in group six a corresponding to six valence electrons where as we stated hydrogen is located in group one, a corresponding to one valence electron multiplied by our subscript of two for the two atoms giving a contribution of two vals electrons for hydrogen. So moving this over, we want to take the total. So we would have six plus two, which also confirms that we have eight films electrons total for this structure. We're told that Toloi has one covalent bond in the prompt for part three. And we can see that Toloi is considered a nonmetal based on its position in group six A. And of course, we know as stated before, hydrogen is also a nonmetal. But in this case, we observe two covalent bonds between hydrogen and Tulo in this structure. And so we would correct this to say two covalent bonds, whereas each hydrogen has one covalent bond is an accurate statement as given in part three because we do observe that in this given electron dot symbol. However, as we stated, tale is a group six A atom and has six valence electrons. And in this electron dot symbol, we only see directly attached valence electrons on tele. So it's missing also a lone pair or rather a second lone pair. Since we do observe a lone pair at the top of the atom, it needs a second loan pair at the bottom to have a full octet. And it's seven or six directly attached val electrons total to have a formal charge of zero. So we would rule out choice three since it's an incorrect structure. And we have one incorrect statement because again, Tulo has two covalent bones. Let's move on to choice four where we have Germanium tetra bromide as our next structure beginning with calculating total valence electrons, starting with Germanium recall that it's a group four a atom corresponding to four valence electrons. And based on its position on the periodic table, Germanium is considered a metalloid. Then we have bromine, which we should recall is a group seven A atom in our halogen group corresponding to seven valence electrons in which the subscript of four in Gebr four tells us that we have to multiply it by our four bromine atoms giving a contribution of 28 val electrons from bromine taking up our total, we're going to add four plus 28 and that's going to give us 32 vals electrons total for this structure. So according to the prompt in part four, Germanium has four covalent bonds. And again, bromine is in our halogen group. So it is also considered a nonmetal. So a nonmetal bond to a metalloid would be a covalent bond. And we do observe that Germanium is sharing four lines to bromine, meaning it has four covalent bonds. So this is correct. Then we have each bromine listed as having one covalent bond. And we can definitely agree with that because we see four lines from each Romine going to our central atom germanium. So this is also a correct statement. Now, calculating total valence electrons, we do observe directly attached four valence electrons to Germanium. So Germanium will have a formal charge of zero and a full lock head since it has four covalent bonds shared to bromine, and then our bromine atoms also de definitely do have directly attached seven valence electrons given by the single electron shared in the covalent bond to Germania that it has attached to itself. And then the three lone pairs on bromine. So on each bromine, and so we would consider bromine also having a formal charge of zero. And therefore, this fourth structure is an accurate structure for its electron dot symbol and the correct number of covalent bonds. So our final answers are choices two and four corresponding to choice D and the multiple choice as our final answer. So I hope this made sense and let us know if you have any questions.

How many covalent bonds are formed by each atom in the following molecules? Draw molecules using the electron-dot-symbols and lines to show the covalent bonds.
a. PH₃
b. H₂Se
c. HCl
d. SiF

Verified video answer for a similar problem:

Key Concepts

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How many covalent bonds are formed by each atom in the following molecules? Draw molecules using the electron-dot-symbols and lines to show the covalent bonds. a. PH3 b. H2Se c. HCl d. SiF

Verified video answer for a similar problem:

Key Concepts

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Lewis Structures

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How many covalent bonds are formed by each atom in the following molecules? Draw molecules using the electron-dot-symbols and lines to show the covalent bonds.
a. PH₃
b. H₂Se
c. HCl
d. SiF