A few gchem questions

[MoooShuuu]

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Some questions I ran into while looking over some material today:

1. Which group contains an element with an elecron configuration of [....]4p6 4d5 5s2
The answer says it is a nonrepresentative element in group VII. There are seven electrons in the outermost shell. Where is this 7 derived from? 5s2? 5+2=7?


2. When asked for the most likely resonance structures... what is a quick way to do so? I understand that the most electroneg atom should have a negative formal charge if there is one. Are there things that I can look for that immediately tell me that it is not the correct structure?

3. When asked about polar and nonpolar molecules...is there another way of telling other than drawing out and seeing if it has a lone pair or is angular in vespr?


Thank you in advance, you all are a great help 🙂

 

[chessxwizard]

1) Yes; the highest principal energy level in the s subshell and the second highest for the d subshell are used to evaluate valence electrons configurations for transition elements.

2) Not sure if this would help on the real thing, but Kaplan usually tries to pull a fast one by drawing structures that have more than 8 electrons per atom that does not have available d-orbitals. That could be one possible way to eliminate answer choices.

3) Unless you know the structure right off the bat, the safest way is to quickly draw a Lewis structure and evaluate the molecular shape.

 

[supraman]

If there is a d oribital in the electron configuration, think transition metal

 

[waystinthyme]

1) Yes; the highest principal energy level in the s subshell and the second highest for the d subshell are used to evaluate valence electrons configurations for transition elements.

2) Not sure if this would help on the real thing, but Kaplan usually tries to pull a fast one by drawing structures that have more than 8 electrons per atom that does not have available d-orbitals. That could be one possible way to eliminate answer choices.

3) Unless you know the structure right off the bat, the safest way is to quickly draw a Lewis structure and evaluate the molecular shape.

1) this is correct, but what the OP did was not correct...you both came up with the same answer by chance. please notice the difference...

OP: 5S2: 5+2 = 7

chessxwizard: Add up elections in the two highest energy shells.

Highest Energy Shell: 5s2 - 2 electrons
2nd Highest Energy Shell: 4d5 - 5 electrons
Total # of Electrons: 2 + 5 = 7

please make sure you recognize the distinction.

2) more than 8 electrons or 4 bonds on normal elements, more than 3 bonds on B/F, positive charge on electronegative elements (ex. O), wrong net formal charge, etc.

Correct Resonance Structures: correct formal charge, - charge on most electronegative element, all elements have the right number of bonds, etc.

3) agree with chessxwizard

-waystinthyme

 

[MoooShuuu]

Can someone tell me how to go about doing this problem:

How many moles of AgIO3 (Ksp 3.1 X 10-8) will dissove in one liter of a 10-5 solution of NaIO3.

Also, given a list of compounds how can you tell if they are able to hydrogen bond or not

for example:

C4H11N
C4H9NO
C4H7F3
C4H8O2--is this one not able to?
C4H10O

I have this Kaplan practice test booklet from a few years ago but no answers so I appreciate your help in explaining these problems.