[RimuruNava]

Hi I am very new to chemistry and I'm studying for an upcoming exam.

I was studying about ions and I got to the part where it says that there are simple ions and polyatomic ions, then I wondered, how are the charges of polyatomic ions determined? I didn't want to simply memorize the few polyatomic ions given to me that will most definitely come up in the exams as I hate memorizing so much and I also want to know. So that is my first question.

Second question is about covalent bonding. Say that the exam question is "draw the electron diagram of compound between Carbon and Chlorine, Carbon and Hydrogen and Oxygen." How can I easily know the number of atoms of each element? It's very annoying since I missed a lesson talking about it during online lessons and I lost a few marks that were very easy after receiving the answers. Oh and also determining whether it is a single or double or triple covalent bonding.

That is all for now, sorry if some sentences don't really make sense as English isn't my first language and so some terms may be a bittt different

[chenbeier]

Polyatomic ions charge is calculated by the oxidation numbers. You have to learn the basics, like hydrogen is +1 normally,  oxygen -2 ,Halogenid -1, Elements 0, also bonding of two same elements., main elements max. Oxidation number is the group number, for example sulfur + 6.

For the example Sulfate it is SO₄^2-

This can be calculated as -2 = 6(S) + 4* (-2)(O)

H₂C=CH₂  0 = 4 *(+1) + 2 (-2), hydrogen +1 , carbon -2