About electrode......

[albertlee]

in my school, when I was being taught about electrolysis, the electrode that offers electrons are called cathode....

 

but as more lectures being given, another textbook says the electrode that offers electrons are called anode....

 

which one is true???

 

Albert

[maverick88]

negatively-charged electrode = cathode

positively charged electrode = anode

[Silencer]

The confusing part is that positive ions are called cations and negatively charged ions are anions.

 

I assume this is because positive ions are attracted to the negative cathode, and the negative ions attracted to the positive anode.

[albertlee]

but HEY!!

 

Look at here: http://www.ectechnic.co.uk/acid.html

 

2. The anode is the electrically negative terminal. Some people find this surprising, since they are wrongly taught that anode always means positive. It does not! The anode is also the correct name for the negative terminal of any primary cell. (See the Oxford English Dictionary!)

 

Albert

[albertlee]

Any body has any idea??

[5614]

positive electrode = anode

negative electrode = cathode

 

postive ion = cation

negative ion = anion

 

that site is weird!

[Gilded]

Man... Why did they have to make electricity so complicated.

[Lance]

I'm deeply disturbed. I think we shouldn’t let these people dictate what we call things and call them whatever the hell we want.

[Gilded]

"I'm deeply disturbed. I think we shouldn’t let these people dictate what we call things and call them whatever the hell we want."

 

Right on, matey. Let's call negative terminals "whatsimagickers" and positive terminals "ropuffkazoodles".

[Ophiolite]

Were these actually two unrelated statements?

 

I think we shouldn’t let these people dictate what we call things and call them whatever the hell we want.

I'm deeply disturbed.

[chadn]

positive electrode = anode

negative electrode = cathode

 

postive ion = cation

negative ion = anion

 

that site is weird!

 

Whats so wierd?

[5614]

Whats so wierd?

i said: "that SITE is weird".... ie the one which disagreed with what i had said, the one which confused albertlee and caused this thread (presuambly)

[Lance]

I seriously always thought of cats being negative making the cathode and cation also negative (as apposed to dogs being negative but not as much so)(the reason Im so disturbed).

 

In 10 years they will probably scrap both names and come up with something completely different. Thats why I say we should call it whatever the hell we want.

[5614]

or you could think of it as....

 

start off with the electrode becaus without em nothing happens!

 

'a' is the beginning, the beginning is good therefore

a = begin = good = postive = anode = positive electrode

therefore negative = cathode

 

and its the other way around for the ions.

 

hmmm, the logic is almost there!

seriously though, thats how i remember it

[jdurg]

I say that the positive electrode should be called the 'posode', and the negative one should be called the 'negode'.

[5614]

hmmm, but this is the real word not what you say... sad isnt it, i get that feeling sometimes too.

 

i tell ya what... being on a science forum and all, im obviously great at languages skills, so i made you a poem.

 

a is the start

a is good

therefore a is positive

which makes

an anode positive too

[Lance]

I say that the positive electrode should be called the 'posode', and the negative one should be called the 'negode'.

 

rofl. I love it. Ill do it if you do.

 

a is the start

a is good

therefore a is positive

which makes

an anode positive too

 

Great but what about the anion? a is good when it comes before node but bad when it comes before nion?

[5614]

oh well ya see.... electrode is first and then after that its all reversed so that the ions attract to the right one

 

just remember it all starts with the electrodes, coz without em nothing happens... and then after that - as usual - its all reversed just to confuse you!!!

 

in that a = negative ion whereas a = positive electrode.

 

here's the update:

 

a is the start

a is good

therefore a is positive

which makes

an anode positive too

and after that it all reverses

[Xavier]

As Albert was asking earlier about fuel cells and the quotation from the site he indicated includes the term 'primary cell' I think that the source of the confusion is that the quoted website is talking about a potential developing cell that develops potential whilst everyone else is thinking only of the potential resisting circuit/electrolyte etc.

 

You will all doubtless recollect that technically, the definition of anode and cathode refers to the direction in which the current is flowing rather than the charge that is developed at the electrode when there is a capacitative gap. The terms, of course predate much of the theoretical understanding of electricity but the fact of the flow and circuit was clear from the beginning.

 

Consider a silver electrode in a solution of potassium chloride, for example. When a positive potential is created in the silver electrode with respect to an inert reference electrode placed elsewhere in the electrolyte KCl solution, electrons move along the wire away from the electrode. A small capacitance is generated between the electrode surface and the bulk of the electrolyte solution as a thin boundary layer around the electrode becomes relatively electron depleted and becomes a bit of an insulator. Chloride ions will be drawn to the positive charge in the vicinity of the electrode and cross the depletion layer, there to grab a silver atom which ionises to give up an electron to the need for current The electrode is positively charged with respect to the solution and the electron flow is attempting to move from the surface of the the electrode into the wire. This is an anode.

At the electrode surface the reaction is: Ag(s) + CL-(aq) -> AgCl(aq) + e-

 

Now think of the situation in a cell (meaning a battery, not biologic etc.) where a chemical potential is driving the chloride ions to the silver electrode and where the the price of completing the overall exothermic (energy releasing) reaction of Cl- ion with Ag atom is to expend some of that energy pushing an electron away from the Ag atom into the electrode thus generating a negative potential difference with repect to the reference electrode which will cause a current to flow from the silver electrode towards the reference electrode.

At the electrode surface the reaction is Ag(s) + CL-(aq) -> AgCl(aq) + e-

exactly the same as the previous example (ignoring the other chemical events elsewhere in the solution that contribute to the overall exothermy of the chemistry)

and the electrons are still flowing away from the electrode surface up the wire so this is still an anode.

However, at the electrode surface there is a net negative charge with respect to the solution!

[albertlee]

thx Xavier, good explanation....

 

In adition to that, the direction where the negative electrode (cathode) offering electrons is the direction where the electrons move out of a power supply......

 

Albert