[Suspicious_boat_5926]

Suppose Im given element sulfur and chlorine. Most of my ability to write chemical formulas from being given these is rote memorization by handling them before, such as CCl3. But Im given C and Cl, S and Cl, etc.

In other words, the elements don't specifically tell me how many parts there are.

Ionics are easier, since they cancel charges, but Im not sure how to deal with molecular.

Supposing I have Sulfur and Chlorine, I would imagine I need to increase the number of one element until the octet rule is satisfied, correct?

How do I know which element? is it based on centrality?

I am to assume only single chemical bonds, so my guess is that central element is plugged in first, and then enough of the other element is added with its charges to make the octet rule.

[Suspicious_boat_5926]

I have just noticed that in moleculars, if one is in period 7, then the amount of period 7 elements is equal to the distance from it to the next element in the molecular. So SBr2, PBr3, SiBr4 and so on. Is this right?

[Hunter2]

Its a matter of electronegativity.
If you have S and Cl , chlorine is more negative as sulphur, so you can make SCl2 and SCl4. If you had flourine, then also SF6 is possible.

SBr2, PBr3, SiBr4

Correct.

But AlBr3, CaBr2 and KBr

[Suspicious_boat_5926]

thank you