Which of the two compounds, H2NNH2 and HNNH, has the strongest ni...

Question

Which of the two compounds, H2NNH2 and HNNH, has the strongest nitrogen-nitrogen bond, and which has the shorter nitrogen-nitrogen bond.

Accepted Answer

welcome back everyone in this example, we need to identify the molecule that has a stronger silicon silicon bond and a molecule with the shorter silicon silicon bond. So we are comparing between silicon tetrachloride and then we would have di hydrogen silicon tetrachloride as our two lewis structures that we need to draw out. So beginning with our silicon tetrachloride, we want to recall that to draw its lewis structure. We need to calculate total valence electrons. So beginning with our silicon atom, recognized that on our periodic table. It's located in Group four A corresponding to four valence electrons. And so we would have our four valence electrons multiplied by R two silicon atoms, resulting in a total of eight valence electrons from the silicon atoms. Now recognizing that chlorine on our periodic table is located in Group seven A. We would recall that that corresponds to seven valence electrons being multiplied by r four atoms of chlorine in this structure. Giving us a total of 28 valence electrons contributed from the chlorine atom. And now taking the total for our total valence, we would have a total of 36 valence electrons total for our lowest structure. So recognizing from the formula we have silicon in the center which are bonded to one another and surrounded by four chlorine atoms. So using up our first two electrons, we made our first two connections to silicon here and as we recall our silicon atoms have four valence electrons, meaning that to be stable. They should have four bonds. And so for our first silicon we're going to make two bonds to these chlorine. Is here, where are fourth bond would be considered? The double bond between our silicon atom and our silicon atom on the right hand side would also have to bonds to chlorine, counting up the total amount of electrons. These bonds used. We have 2468, 10 12 electrons. We've used so far so we can subtract that from our total leaving us with valence electrons left over to use as lone pairs on our chlorine atoms. Where we would have 2468, 10 12 14 18 2022 and 24. The rest are completing the rest of our valence electrons as lone pairs on our chlorine atoms. For silicon tetrachloride. Now we want to go ahead and draw our structure for di hydrogen. Silicon tetrachloride. Next. So that's H two S I two c L. Four. Where we need to calculate total valence electrons first as before. So beginning with hydrogen, we recognize that it's in Group one A corresponding to one valence electron multiplied by our two atoms of hydrogen, which would give us a total of two electrons. Moving on to our silicon atoms. We also recognize that silicon, again located in Group four A. On our periodic table corresponds to four valence electrons multiplied by r two atoms, giving us a contribution of eight electrons. And then for our chlorine atoms, we recognize that chlorine is located in Group seven A of our periodic table corresponding to seven valence electrons multiplied by our four atoms, Which would give us a total of 28 electrons contributed from chlorine. Taking the total of valence electrons, we would have a total of 38 valence electrons. So drawing out our structure, we have again our silicon atoms in the center bonded to one another, where we have our four chlorine atoms still surrounding our silicon atoms. And then at the bottom we have our silicon atoms surrounded by two hydrogen atoms. Never called that are hydrogen atoms only have one valence electron and can therefore only form a single covalin bond to our silicon atoms, meaning right now each of our silicon atoms have a total of three bonds. And so we're going to continue our structure by connecting our silicon atoms to and correction each of our silicon atoms have a total of two bonds right now based on our structure. And so now we're going to connect the rest of our atoms being our chlorine atoms to these silicon atoms. So we would have 1234 more bonds added where we would recognize that each of our silicon czar happy and stable because they have their four valence electrons being shared in covalin bonds with either two chlorine atoms and one hydrogen atom on both sides of our structure here and then with one single bond between each other here. So this is actually going to When we count up our electrons use a total of 2468, 10, 12, 14 of our valence electrons. So subtracting that from our 38, that would again leave us with 24 valence electrons which we would use as lone pairs on each of our chlorine atoms. And we can see that in doing so. We've used up all of our electrons and based on these two structures, we can see that we have the presence of an alkaline or rather pi bond between our silicon atoms in our silicon tetrachloride. And because we have this pi bond, we want to recall that pi bonds are stronger and shorter. And so for our final answer, the molecule that has the stronger silicon silicon bond and the molecule with the shorter silicon silicon bond is going to be our silicon tetrachloride as our final answer. So I hope everything I reviewed was clear. If you have any questions, leave them down below and I will see everyone in the next practice video

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