[sukarian]

hello

i am a high school chemistry student
we are talking bout ion charge
my teacher says +2 is ok (example - Mg+2)
but i have seen in books it always says Mg 2+

is there any difference?
what is the difference?
what do they mean; if they are different?

also, if they are different or they are the same - can anyone show me a book or a page of a book so i can show as proof


thank you

[opti384]

It's usually written as 2+. The number comes afterwards.

[sukarian]

my question is :

is it wrong to write +2  ?  (example - Mg+2)  ??

does it have a different meaning?

my teacher always writes Ca+2 , but our book says Ca 2+

teachers says it is the same thing. Is that true ?

does it have a different meaning if i write Ca +2  ??

is there an example in a book?

[Borek]

The ultimate source of knowledge here is IUPAC Green Book, General Chemistry section, Other symbols and conventions in chemistry (2.10.1), (i) Chemical symbols of the elements.

Al³⁺ is commonly used in chemistry and recommended by [69]. The forms Al⁺³ and S^-2, although widely used, are obsolete [69]

[69] is a book Nomenclature of Inorganic Chemistry, G.J.Leigh (editor), Blackwell, Oxford, 1990.

Note that Mg+2 notation in some cases is much safer - SO4-2 is less ambiguous than SO42-.

[sukarian]

hi

i found the link to the Green Book and the page you quoted
above your quote, i see where it says:  Al 3+  or  Al +3 . 3S 2-  or   3S -2

so it says both are ok - right ??

my question:   Do they have different meaning ?

my teacher emphasizes Mg+2 is wrong
i ask - why ? does it have a different meaning ??
he only replies - "it's not correct!"

he is a chinese man - maybe that explains it, but WHY is it NOT correct ??

Additionally - i found in the IUPAC Red Book - http://old.iupac.org/publications/books/rbook/Red_Book_2005.pdf
IR-4.3 Indication of Ionic Charge . it says ... "as in A n+ or A n- (not A +n or A -n)."
soooooo, which is correct ?? Teacher, book , etc .?
What is the difference in Green Book and Red Book ?

Again i ask - what is the difference? Different meaning of the two ?

any more references ??  that may help me

[rabolisk]

In your first post, you said that your teacher says +2 is ok. Then in your last post, you said the opposite. Which is it?

...Do they have different meaning ?


Jokes aside, 2+ is more correct than +2. It's analogous to the fact that Group 16 is more correct than the obsolete Group 6 to refer to the oxygen group (chalcogens), or that the term lanthanoid is more correct than lanthanide.

[sukarian]

in the confusion and frustration maybe i said wrong

either way: the arguement is : Which is correct ?

if 1 is correct , is the other wrong ?

is 1 MORE correct than the other ? or , is it absolutely wrong ?

if it is wrong , why ? does it have a different meaning?

if the "bible" is the GREEN book - page 44 of 2nd edition green book (section 2,10 ii)

http://old.iupac.org/publications/books/gbook/green_book_2ed.pdf

clearly says " The ionic charge is denoted by aright superscript, or by the sign alone when the charge is equal to one."

It goes on to list examples:

Examples: Al³⁺ or Al⁺³

this is more clear than the previous link provide to me of the DRAFT of this book

the draft says this form (Al⁺³) is now obsolete and refers to a 1990 publication   

http://www.iupac.org/reports/provisional/abstract05/GreenBook051206_prs.pdf   (page 49 of this book - the draft)

the final draft does not include that and show EITHER is ok !

maybe i am answering my own question, BUT, this has turned into a heated discussion between students AND teacher/students.

any further input is welcome and appreciated !

thank you

[rabolisk]

What matters is whether professionals in the field of chemistry and in the wider fields of science understand what is meant by Al³⁺ and Al⁺³. I think that most will understand that both mean aluminum with a charge of +++, so from my perspective, whether or not 3+ or +3 is "correct" is somewhat irrelevant. I think a motivation for using 3+ over +3 is to differentiate between charge and oxidation state. I would use 3+ over +3 as this is becoming standard practice and is least confusing. The IUPAC would probably consider +3 to be wrong, but some will not.

[Borek]

Ask your teacher (politely) on what source he based his information.

I see that I have fallen into trap, following fast link from wikipedia - I quoted draft, not the current version. My mistake.

Unfortunately draft is not searchable, as far as I can tell it doesn't define precisely how to understand "obsolete" (sometimes manuals do define such terms to avoid ambiguity in some specific situations). Most likely it means you should understand what it means when you see it, but you should not use it in new places. Even if it is a draft, it sounds like a reasonable rule.

[sukarian]

hi

great reply and information you provide

as for ion or oxidation: green book p.44 section 2.10 ii
    says: (my paraphrase) - ion are represented by X³⁺ OR X⁺³

after that section, it addresses Oxidation
"Oxidation numbers are denoted by positive or negative Roman Numerals or by 0 (see also section iv below)"

then, a few examples follow of Oxidation: "Mn^VII" "O^-II" "Ni⁰"

i believe we are getting "nit picky", but the i want the proof for this teacher
i do not remember seeing Oxidation with roman numerals - but THEY say it is the correct way.

What is the difference in Oxidation and an Ion ?  Same ? Pretty much the same ?

As for the source of his info: some 2nd rate manuscript written on rice paper in red China that he believes is the gospel and their is no deviation from that (very closed minded individual).

The other chem teacher in our school DID say either is acceptable to/for him and he understands both methods. He said he learned chem long time ago and today, he writes Al⁺³, and nobody has ever corrected or questioned him.

But this china man is profound ; 1 is correct and 1 is wrong.

If we take the "Green Book" as the Chemistry (IUPAC) bible - it does spell out the difference clearly, and it says either is acceptable.

I think both would be understood by individuals in the chemistry world/field, and that is most important (as was said)

again - maybe i am answering my own question
but i am also seeking the knowledge and perspective of more educated individuals

thank you again

[rabolisk]

Like I said, I would personally accept both 2+ and +2 to denote charge of an ion. I am used to using n+ rather than +n for ions, and this is the standard method I encounter in modern textbooks. This is why it can be considered perhaps "more correct" only because it is more standard.

Also, there is a difference between oxidation number and oxidation state, as well as between those two and charge of an ion, although all are related to the concept of electrical charge and loss/gain of electrons.

http://en.wikipedia.org/wiki/Oxidation_number
http://en.wikipedia.org/wiki/Oxidation_state

[AMEDIO]

both mean the same....