Expanded Valence Shells

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Jasmine 2C
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Joined: Wed Sep 18, 2019 12:18 am

Expanded Valence Shells

Postby Jasmine 2C » Fri Nov 01, 2019 1:40 am

How do we know how many electrons elements with expanded valence shells can hold?
Like in the example from lecture, the slide says "P in phosphorus pentachloride PCl5 has 10 valence e- (s2p6d2) using 1 d-orbital". How do we know that phosphorus can hold 10 valence electrons?
And from a homework question 2C.11"Draw the Lewis structure and state the number of lone pairs on xenon, the central atom of each of the following molecules: (a) XeOF2; (b) XeF4; (c) XeOF4" how do we know that the Xn in XeOF4 can hold up to 14 valence electrons?

Posts: 55
Joined: Thu Jul 11, 2019 12:17 am

Re: Expanded Valence Shells

Postby SGonzales_3L » Fri Nov 01, 2019 9:53 am

I think it helps to fill all the other typical atoms first (e.g. H, O, F, Cl, etc.) since these are most likely to abide by the octet rule. Then, draw bonds to the central atom. One good tip is to count how many electrons/electron pairs are in the molecule/formal unit. If all the typical atoms already have full octets, it is highly likely that the leftover electrons will go around the atom that can accommodate more than 8 electrons. Since they can fill their d-orbitals, the number of electrons these atoms can accommodate varies. Just add them based on how many electrons are leftover and then calculate formal charges.

Sartaj Bal 1J
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Joined: Thu Jul 25, 2019 12:17 am

Re: Expanded Valence Shells

Postby Sartaj Bal 1J » Fri Nov 01, 2019 11:21 am

Usually, elements in the P-block of Period 3 or later periods have the ability to form an expanded octet. For example, we can compare Nitrogen in Period 2 and Phosphorus in Period 3. P is a larger atom than N as demonstrated by the greater atomic radius so as a result, it is an exception to the octet rule.

Kassidy Ford 1I
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Re: Expanded Valence Shells

Postby Kassidy Ford 1I » Fri Nov 01, 2019 3:13 pm

what is the most electrons an expanded valence shell can have? 10? 14? is it different for different atoms?

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