valency!?

[silverwind]

i am totally confused on this concept!how is valency determind?how can we have H^- and H⁺,what is their valency,how to tell valency of an atom,octet rule,would somebody plz help me?how does it work,and how are symbols assigned.need urgent help!!!exam after three days!!

 

being more specific,i want to know about the positive and negative signs in valency.for example,in an equation, we write cl as cl^-. why?and so on.i want to know how are these positive and negative signs determined.thnx

[mississippichem]

An atom with different numbers of protons and electrons will have a net charge and is called an ion. So [ce] Cl^-^ [/ce] has one more electron than it does protons.

 

Now take hydrogen for example. It has one proton and one electron. If it gains an electron, that's [ce] H^-^ [/ce]. If it loses an electron, that's [ce] H^+^ [/ce]. Now it just so happens that hydrogen only has a 1s orbital (H is in first period, first group). So hydrogen is limited to 2 electrons because an s-orbital holds 2 electrons and no more.

 

So an ion with a 3+ charge would be missing 3 electrons from the atoms neutral configuration.

[Horza2002]

Mississippichem has explained it well. I just want to point out that hydrogen does have higher energy levels than 1s. However, they are so high in energy that they are hardly ever filled. So in principle, you can have H(-3) but you'd be extremely hard pushed to make it

[silverwind]

thank you,what will be the valency of an ion like X^-2?will it be -2,or +2