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You can basically put them anywhere as long as they satisfy the octet rule (there are some elements that are exceptions to this because they have an expanded octet) meaning they have 8 valence electrons in the outer most shell after bonding with other atoms
Adding on to the poster above, the location of double and triple bonds will depend on where the octet rule can be accommodated. They cannot be replaced wherever “because of resonance,” because we must also determine if the atom has resonance structures in the first place. If there is resonance, then be sure to calculate the formal charges of the atoms in the structure you have set up.
Double and triple bonds should be placed when the number of electrons does not allow for single bonds only + valence electrons for each atom, so electrons must be shared so they can be "counted twice" like he mentioned in lecture.
In general, hydrogen likes to have one bond, oxygen likes two, nitrogen likes three, and carbon likes four. When you decide where to put double bonds or triple bonds, arrange them so that the most atoms have 0 formal charge and all the electrons are used, which usually follows the rules above.
Like Dr. Lavelle did in lecture, I would add up all of the valence electrons present in the compound, also taking into account the charge of the compound, first. Then, I would place the element with the lower ionization energy as the central atom. Arrange the other atoms around the central atom and begin by giving a single bond to the central atom and the outer elements, as well as completing an octet for each outer atom. Then, see if you took account for all the electrons that need to be present in the compound, which is why you added them all up in the first place. Place the double or triple bond accordingly. If there is resonance, be sure to draw all of the Lewis structures to account for the different locations the double or triple bond may be.
If there are multiple places where you could put the double or triple bond, you have resonance which means that you can draw the bonds anywhere in the lewis structure and that the actual experimentally observed bond length is an average of all the bond lengths.
Our TA told the HONC rule where H likes to have 1 bond, O likes to have 2, N likes to have 3, and C likes to have 4. If any of these elements are in the molecule you are trying to draw, follow this rule to help.
A good place to start is when looking at the number of electrons in a chemical species, and drawing the lewis dot structures, if a species is meant to have multiple bonds, the number of e- drawn should not match the total number of electrons needed.
In most cases, double bond placement does not really matter as long as you fulfill the amount of electrons required to represent the molecule and that you follow the octet rule. If you see Hydrogen, Oxygen, Nitrogen, or Carbon, just note that Hydrogen prefers 1 bond, Oxygen (2), Nitrogen (3), and Carbon (4). Knowing those bond preferences would also make it easier to determine how to create the structure itself.
Due to the concept of resonance, technically double and triple bonds can be anywhere as long as the satisfy the octet rule. Just make sure to count up all the electrons before you place the double and triple bonds in a certain location
If a double bond occurs, then does that mean that the lone pairs are interchangeable without it effecting the lewis structure (for instance, like in nitrate NO3)? Like can the double bond occur at any pair of the oxygen without there being a difference?
they can be placed as long as they satisfy the octet rule but you should try drawing a structure with zero formal charge because it will be most stable. the double/triple bonds will help getting the formal charge to zero
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