HW 3.39

[Maya Khoury]

3.39 asks you to draw the lewis structures for (a) ammonium chloride, (b) potassium phosphide, and (c) sodium hyphoclorite

My first question is will we be expected to know the empirical formula for these on our own?
And secondly, for part a for example, why in the lewis structure does NH₄ have a positive charge and Cl have a negative charge? My friend said this has to do with it being an ionic bond and not a covalent bond.
Lastly, why for part b, does phosphorus have a 3- charge? and Potassium has a positive charge? (same type of question as above)

hope my questions make sense!

[AshleyLamba1H]

To answer your first question, the chem mods have said on other posts that you do not need to know how to find the molecular formula when given the name of a molecule. On exams, the molecular formula will be given.

[Joshua Yang 1H]

3.39 asks you to draw the lewis structures for (a) ammonium chloride, (b) potassium phosphide, and (c) sodium hyphoclorite

My first question is will we be expected to know the empirical formula for these on our own?
And secondly, for part a for example, why in the lewis structure does NH₄ have a positive charge and Cl have a negative charge? My friend said this has to do with it being an ionic bond and not a covalent bond.
Lastly, why for part b, does phosphorus have a 3- charge? and Potassium has a positive charge? (same type of question as above)

hope my questions make sense!

For NH4, if you calculate the Formal charge, you get overall +1 (from N), and also, a Chlorine atom in its natural state is usually found as an anion with -1 charge

Same goes for phosphorus and potassium. Phosphorus usually exists as a -3 anion, while potassium exists as a +1 cation. We can find this by looking at the location of the element on the periodic table, as most atoms try to fit with the octet rule.

[Maya Khoury]

okay this makes a lot of sense! could someone explain how by looking at the periodic table you know what elements are generally anions or cations? and how can you tell if they're 1+ or 3+ for example?