[Guest]

Yeah, and here I was thinking I wouldn't have to use this thread *How vain of me*

So I have a test on Friday on a lot of chemistry stuff that I missed while I was sick with Strep Throat. I understood most things, but the thing I'm stuck with is Isotopes and Ions. My sheet says that Isotopes are written like so:

C-11

C-12

C-13

C being Carbon...But what are those numbers? What do they mean, and why are they different?

Next in the book talks about Ions and Ionic Bonding. Here is where I'm REALLY confused. The teacher gave me a sheet on how to draw Bohr Rutherford Diagrams...and said they'd help, but I don't really understand what I'm supposed to be doing...anyone willing to lend a hand?

<(^-^)>

Edit: Clarification

Edited March 2, 2009 by Kathleen

[Guest]

Yeah, and here I was thinking I wouldn't have to use this thread *How vain of me*

So I have a test on Friday on a lot of chemistry stuff that I missed while I was sick with Strep Throat. I understood most things, but the thing I'm stuck with is Isotopes and Ions. My sheet says that Isotopes are written like so:

C-11

C-12

C-13

C being Carbon...But what are those numbers? What do they mean, and why are they different?

A snappy definition we had to learn about isotopes was somthing along the lines of:

Isotopes are atoms of the same chemical element with the same chemical properties that differ only in the number of neutrons they contain.

that might be less than what you need to know, so check in your textbook to make sure

from the italics you can probably tell what those numbers are now - but again, quick check on the internet or in your textbook could help you out too.

[Guest]

So then C-11 would be Carbon with 11 neutrons?

<(^-^)>

[Izzy]

So then C-11 would be Carbon with 11 neutrons?

<(^-^)>

Precisely.

As for the Bohr diagrams, it's really simple. Make a circle, and either write or draw the given amount of protons and neutrons inside, making sure to label properly. Find out how many electrons your element has, and begin putting the electrons in place by drawing "outer shells". The first outer shell is able to hold two electrons, but then it is full. The next can hold eight. I forget exactly how many each shell can hold, but I'm sure a quick peak through the textbook will tell you. Basically, as long as the outest outer shell (if that's termed correctly?) isn't full, the element will search for another element that it can easily bond with. That's why hydrogen bonds so much, its outer shell only has one electron, and wants to have another one for it to be stable.

If that makes sense. Sorry, it's been a while. >_>

[Guest]

Precisely.

As for the Bohr diagrams, it's really simple. Make a circle, and either write or draw the given amount of protons and neutrons inside, making sure to label properly. Find out how many electrons your element has, and begin putting the electrons in place by drawing "outer shells". The first outer shell is able to hold two electrons, but then it is full. The next can hold eight. I forget exactly how many each shell can hold, but I'm sure a quick peak through the textbook will tell you. Basically, as long as the outest outer shell (if that's termed correctly?) isn't full, the element will search for another element that it can easily bond with. That's why hydrogen bonds so much, its outer shell only has one electron, and wants to have another one for it to be stable.

If that makes sense. Sorry, it's been a while. >_>

Oh! I think I get it! Er...but something does add up for Isotopes...if C-11 has eleven neutrons...and neutrons + protons = the average mass...and the proton equals the atomic number...that doesn't make sense

<(^-^)>

[Guest]

So then C-11 would be Carbon with 11 neutrons?

<(^-^)>

Actually that would mean that carbon has 11 particles in the nucleus.

so 11 being the total mass, you need to take the number of protons, which is constant for every atom, from the total.

so

11 total = 6 protons (because we're dealing with carbon) + no. of neutrons,

which means

11 total - 6 protons = no. of neutrons

[Izzy]

Oh! I think I get it! Er...but something does add up for Isotopes...if C-11 has eleven neutrons...and neutrons + protons = the average mass...and the proton equals the atomic number...that doesn't make sense

<(^-^)>

Umm.. I don't think the atomic mass is the protons plus the neutrons? And if it is, that's why isotopes have different masses?

atomic mass

the quantity of matter contained in an atom of an element. It is expressed as a multiple of one-twelfth the mass of the carbon-12 atom, 1.992646481023gram, which is assigned an atomic mass of 12 units. In this scale 1 atomic mass unit (amu) corresponds to 1.660538731024gram.

[Izzy]

Well, there you go then. Listen to Romulus, as he's probably more qualified than I am in chemistry, and seems to know what he's talking about. I vaguely remember this stuff, and obviously not as good as I thought I did. >_>

[Guest]

Actually that would mean that carbon has 11 particles in the nucleus.

so 11 being the total mass, you need to take the number of protons, which is constant for every atom, from the total.

so

11 total = 6 protons (because we're dealing with carbon) + no. of neutrons,

which means

11 total - 6 protons = no. of neutrons

Oh I get it now...thank you so much :3

<(^-^)>

[Guest]

Umm.. I don't think the atomic mass is the protons plus the neutrons? And if it is, that's why isotopes have different masses?

atomic mass

the quantity of matter contained in an atom of an element. It is expressed as a multiple of one-twelfth the mass of the carbon-12 atom, 1.992646481023gram, which is assigned an atomic mass of 12 units. In this scale 1 atomic mass unit (amu) corresponds to 1.660538731024gram.

Atomic mass by definition is the sum mass of all the electrons, neutrons, and protons in an atom

the sum of the masses of the electron and proton equal the equivalent of a neutron,

1 amu is equal to the mass of a normal hydrogen atom which is composed of 1 electron and 1 proton.

Is as simple as 1 + 1 =2

[andromeda]

Romulus is correct... Izzy stop confusing Kat, I know you are only trying to help but you are mixing the atomic mass with the relative atomic mass!

[Guest]

Atomic mass by definition is the sum mass of all the electrons, neutrons, and protons in an atom

the sum of the masses of the electron and proton equal the equivalent of a neutron,

1 amu is equal to the mass of a normal hydrogen atom which is composed of 1 electron and 1 proton.

Is as simple as 1 + 1 =2

Wait...so if

Electrions (E) + Protons (P) = Neutrons (N)

and

E + P + N = Atomic Mass (AM)

Why don't my number's work? I have a chart to fill out...the question marks I have to fill in...

Protons      Neutrons           Electron      Atomic Mass         Symbol        Name


[/b]    6            ? (12?)              6               14                     ? (Mg?)       ?


[b][/codebox]

[/b]

So

E + P = N

6 + 6 = 12

But

12 + 6 + 6 = 14???

I'm confused >.<

<(^-^)>

Edited March 2, 2009 by Kathleen

[Izzy]

You need to have 8 neutrons. Because since electrons weigh virtually nothing, protons + neutrons = atomic mass.

[Izzy]

Izzy stop confusing Kat, I know you are only trying to help but you are mixing the atomic mass with the relative atomic mass!

Kat, atomic mass = protons plus neutrons, with different amounts of neutrons creating different isotopes.

Relative atomic mass = the average of all the isotopes, done a certain way, and I'm pretty sure this is what's written on the Periodic Table.

Like,the atomic mass of chlorine is 35, 36 or 37, but the relative atomic mass is 35.4532.

Have I redeemed myself?

[Guest]

You need to have 8 neutrons. Because since electrons weigh virtually nothing, protons + neutrons = atomic mass.

OH so it's not

E + P + N = AM

It's

P + N = AM

That clears things up :3

<(^-^)>

[Guest]

OH so it's not

E + P + N = AM

It's

P + N = AM

That clears things up :3

<(^-^)>

Don't pay any heed to my second post, it's just a bunch of random junk you don't need to know about.

[andromeda]

Kat, atomic mass = protons plus neutrons, with different amounts of neutrons creating different isotopes.

Relative atomic mass = the average of all the isotopes, done a certain way, and I'm pretty sure this is what's written on the Periodic Table.

Like,the atomic mass of chlorine is 35, 36 or 37, but the relative atomic mass is 35.4532.

Have I redeemed myself?

Actually chlorine only has two common variations - the most common are 35 and 37, while 36 is radioactive and extremely rare. The ratio of 35 and 37 is 3:1 I think.

Edited March 3, 2009 by andromeda

[Izzy]

Actually chlorine only has two common variations - the most common are 35 and 37, while 36 is radioactive and extremely rare. The ratio of 35 and 37 is 3:1 I think.

Okay, but still. Lookit, I made Kat unconfused.

[Guest]

Er...so now there are variations? NOW what? >.<

<(^-^)>

[Izzy]

We confused Kat again. >_>

Yeah, but you don't have to worry about that from what I can tell. You just need to be able to figure out how many neutrons and protons are in the isotope, right?

[Guest]

Yeah, pretty much :3 Thanks guys XD

<(^-^)>

[Guest]

OK lets see if I can add to the confusion.

An element is defined by the number of protons it has. (The number of neutrons does not affect the chemical properties of an element, merely some of the physical properties and even then not drastically.)

Helium will always have two protons. Otherwise, it wouldn’t be helium. Hydrogen will always have one proton. Etc.

Hydrogen comes in three (maybe more but I’m not aware if they’ve been discovered yet) isotopes;

Normal hydrogen which has one proton and one electron (the number of electrons always matches the number of protons in an element, if it doesn’t it becomes an ion – I’ll get to that later).

Deuterium has one proton, one neutron and one electron. Being heavier, it has a higher melting point and boiling point but only by a few degrees.

Tritium has one proton, two neutrons and one electron. This gives it an atomic mass of 3 but it still keeps the atomic number of 1. Using your notation it would be written as H-3

Regarding atomic mass. E + P + N is correct but electrons are so light in comparison to protons and neutrons that they don’t count. P + N is much simpler.

Ionic bonding: This bit is going to be fun as nobody’s mentioned it yet apart from the opening post.

Izzy is right with explaining about the electron shells. The easiest way to find out how many electrons fits into a shell is to count how many elements are in that row of the periodic table. The innermost shell relates to the top row of the periodic table so only has space for two electrons. The next shell has room for eight, the same as the number of elements in the second row.

Complete shells are stable. Elements with the outermost shell that is one or two off (either plus or minus) a complete shell will try to bond ionically i.e. electrons (or an electron) are (is) transferred from one reactant to the other.

Sodium Chloride (NaCl) is the easiest example (and most common as it is known as table salt). Sodium has one electron in its outer shell and chlorine is one short of a complete shell. Sodium becomes a sodium ion (Na+) and chlorine becomes a chlorine ion (Cl-). The positive and negative charges arise because there is an imbalance between number of electrons versus number of protons for each ion.

I believe the diagrams being referred to are very useful for describing different chemical bonds. They show a much simplified element and show what happens to the different electrons. I know them as dot and cross diagrams.

This is my best attempt for NaCl:

So the outermost electron moves from the sodium to the chlorine so that they now both have a complete outermost shell.

Y-San should be able to correct any of my mistakes (or most people I expect) but let me know if I’m unclear on anything.

Edited March 4, 2009 by UKJon

[Guest]

Funnily enough I also missed this topic whilst I was ill, and I know that it is hard to grasp whilst only getting 1/2 the info with people trying to guide you. I just needed someone to state the obvious points out and I worked out the rest myself. A quick list points should help out here;

1. On the periodic table each Element has an atomic number. This is the number of Protons it has. There is an equal number of protons and neutrons in each element. A Proton has a charge of +1 and an electron of -1.

2. Each element has a "Relative atomic mass". This is a weighted average of every atom of each element e.g. Chlorine has a mass of 35.5. This is because there is Chlorine 35 and chlorine 37 in the ratio of 3:1.

3. The Atomic mass - the atomic number = the number of neutrons. Electrons are roughly 1/1840th of the size of a proton/neutron so dont worry about them

4. An Isotope is an atom that has the same atomic number as its element, but a different Atomic Mass. This is because it has more or less neutrons. Carbon 12, Carbon 13 and Carbon 14, since they are all carbon we can be sure that the atomic number is the same in all of them (6), so the variance in atomic mass is due to a different number of neutrons. This makes them Isotopes

Ionic Bonding...

1. Ionic Bonding only takes place between a metal and non metal.

2. The metal TRANSFERS 1 or more of its electrons to the non-metal, giving both atoms full outer shells.

3. The metal then becomes a POSITIVE ion as it has more protons than electrons. If it loses 1 electron then it has a chrage of +1, 2 electrons it is +2 etc etc... The non-metal gains these electrons and becomes a NEGATIVE ion. If it gains 1 it is -1.

UKJons diagram explains it pretty well. The lone electron in the Sodium atom in its outer shell moves to the nearly full outer shell of the Chlorine atom. This gives both elements a full outer shell and since 1 element is +1 and the other is -1 they opposite charges attract to each other.