please will someone reply asap i need help with this big time

[elerrina]

hi we are doing about atoms uin chem and we have this homework on it and we need to know how to work out how to find the number of protons neutrons and electrons the text book doesnt explain it very well please could some one explain it to me clearly thanks

[mibn2cweus]

click here

[mibn2cweus]

http://education.jlab.org/qa/pen_number.html

[jake-the-peg]

An atoms atomic number is the number of protons in it's nucleus. It has to be electrically neutral so there are the same number of electrons.

The atomic weight can at this level be considerred just as the number of protons and neutrons in the nucleus.

So take Lithium with an atomic number of 3 and an atomic weight of 6.94

It has 3 protons and 3 electrons we round the mass up to 7 and 7-3=4 so it has 4 neutrons.

[Gef]

elerrina please let me know how you got on or if you still need more help. The answers to this and your earlier post are all full of errors.

Perhaps you could post a typical example of the questions you have been asked.

[jake-the-peg]

Yes Gef we know that the atomic weight is not actually the combined number of nucleons because of binding energy and that the term atomic weight should be replaced with relative atomic mass based on carbon 12.

But I'm guessing the questionner isn't a final year physics student and needs the simple answer right now.

[mibn2cweus]

Gef, If I post the incorrect answer to a science question just point out that mibn2cweus is just a goof ball tryin to look smart and give them the correct answer 4 kryin out loud! Tanx! {:~)

[Gef]

Jake I wasn't even thinking about the effects of binding energy. The problem lies with the confusion of relative atomic mass (aka atomic weight ) and mass number. In order to work out the number of neutrons you need to subtract the atomic number of the ELEMENT ffrom the mass number of the particular ATOM. Relative atomic mass gives no information about the number of neutrons and that is why I asked elerrina for more info.

By the way, here in Scotland this is taught to year 10 pupils not final year physics students.

[bobtheduck]

scary stuff

[jake-the-peg]

that's

[jake-the-peg]

I'll say that again!

That's the point Gef. This is clearly a year 10 question not somebody struggling with the quantum model of the atom.

This basic model of the atom is taught down here at an early level too.

Though I've no idea why kids don't laugh and ask why the protons don't fly apart and why the electrons don't fly in and hit the nucleus.

Guess it shows how much you take on trust from teachers

[Gef]

Actually jake the brighter ones do ask. I always try to explain it at their level rather than a bland wait until you are older.