Cation/Anion question

[positron]

In chemistry, the cation is the positive electrode and the anion is the negative electrode. So far so good.

 

Why has physics changed these around? In Geissler tubes the anion is now positive and the cation is now negative. Why isnt there a convention for charges?

[silkworm]

In chemistry, as far as I know in electroplating, the cathode is where the electrons enter the water bath and so cations are attracted to it, and the anode attracts negative charges.

 

A cation is actually the name given for a positively charged atomic species and an anion is a negatively charged atomic species.

[woelen]

Silkworm is right, cathode and anode are not the ions, but the electrodes.

 

The names are indeed somewhat confusing. Formulating it in the way, as given below, may help you remember the correct terms.

 

Cathode --> Negative pole, and cations go to the cathode, they are positively charged and go to the negative pole.

Anode --> Positive pole, and anions go to the anode, they are negatively charged and go to the positive pole.

[sophster]

My old chemistry teacher at college told us a really naff way to remember the positive charge of a cation with a really lame pun,

 

cations are pussitive*

 

Remembering that makes it easy to remember that cations go to the cathode which obviously can't be positive as well so it must be negative and then anions and anodes are the opposite.

 

* sorry about the spelling, it edits the whole thing if I spell it with a y instead of an i!

[jdurg]

The way I learned to remember is that cations are positive and are attracted to the cathode, therefore the cathode has a negative charge.

 

Anions are negative and attracted to the anode, therefore the anode has a positive charge.

 

That makes it pretty easy to remember. In addition, by remembering that it makes it easy to see where the hydrogen and oxygen will form when electrolyzing water. Hydrogen comes from the H+ ions, so it will arise on the cathode which is the negative electrode. Oxygen is the opposite, so it will form on the anode.

 

In addition, the little pneumonic "An Ox, Red Cat" shows that oxidation (loss of electrons) happens at the anode and reduction (gain of electrons) happens at the cathode. In order to gain electrons it would have to mean that the cathode would need a large number of electrons present, thus giving it a negative charge.

[YT2095]

My old chemistry teacher at college told us a really naff way to remember the positive charge of a cation with a really lame pun' date='

 

[i']cations are pussitive*[/i]

 

Remembering that makes it easy to remember that cations go to the cathode which obviously can't be positive as well so it must be negative and then anions and anodes are the opposite.

 

* sorry about the spelling, it edits the whole thing if I spell it with a y instead of an i!

 

ROFLOL, That is Exactly the same saying as I was taught too

 

equaly Lame (but it worked) was to look at the word "Cathode" as being alot longer than the word anode, longer like a Line, like a - line

 

well hey, it worked for me

[positron]

thanks, things are a bit clearer now