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Topic: A helium nucleus has two protons and two neutrons.How many electrons would it ta  (Read 26306 times)

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Offline Bjc51192

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A helium nucleus has two protons and two neutrons.How many electrons would it ta
« on: January 30, 2011, 01:19:49 PM »
Ok I already have the answer, but I dont understand why the answer is 7000.

Helium has a mass of about 4.00 and the mass of an electron is 0.0055(amu) How in the world did they come up with 7000?
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Offline sjb

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #1 on: January 30, 2011, 02:33:34 PM »
Quote from: Bjc51192 on January 30, 2011, 01:19:49 PM
Ok I already have the answer, but I dont understand why the answer is 7000.

Helium has a mass of about 4.00 and the mass of an electron is 0.0055(amu) How in the world did they come up with 7000?

If I have a football that weighs 400g, and marbles that weigh 4g, how many marbles do I need to weigh the same as the football?
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Offline Bjc51192

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #2 on: January 30, 2011, 02:49:30 PM »
Quote from: sjb on January 30, 2011, 02:33:34 PM
Quote from: Bjc51192 on January 30, 2011, 01:19:49 PM
Ok I already have the answer, but I dont understand why the answer is 7000.

Helium has a mass of about 4.00 and the mass of an electron is 0.0055(amu) How in the world did they come up with 7000?

If I have a football that weighs 400g, and marbles that weigh 4g, how many marbles do I need to weigh the same as the football?

100? but I dont understand what I did was multiply 4.00 (0.0055) and divide that answer by 1 and got 0.22. Is their a certain step that I am missing?
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Offline sjb

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #3 on: January 30, 2011, 03:07:11 PM »
So for my example you did the sum 400 ÷ 4, but for yours, did you not do 4 ÷ 0.0055 ?
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Offline Borek

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #4 on: January 30, 2011, 03:26:18 PM »
Quote from: Bjc51192 on January 30, 2011, 02:49:30 PM
what I did was multiply 4.00 (0.0055)

You are multiplying what by what in hope of getting what?

Are you sure it is 0.0055? Doesn't look to me like it will give 7000, unless my calculator is failing me.
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Offline Bjc51192

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #5 on: January 30, 2011, 03:43:44 PM »
No. im just going by what my book said the mass of an electron was. I looked it up it said is 0.00055, but that doesnt seem to give the right answer
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Offline Borek

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #6 on: January 30, 2011, 05:04:12 PM »
0.0055 and 0.00055 are two different numbers.
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Offline Bjc51192

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #7 on: January 30, 2011, 05:14:39 PM »
Reguardless I cant get the answer.
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Offline Borek

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #8 on: January 30, 2011, 05:51:19 PM »
I asked you a question, two posts ago.
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Offline Bjc51192

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #9 on: January 30, 2011, 07:52:05 PM »
Since the mass of an electron is about 1/1837th the mass of a proton, then it will take many, many electrons to equal the *mass* of the helium nucleus. Since the mass of of the helium nucleus is approx. 4.00 amu, then ...

4 amu x 1837 electrons /1 amu = 7348 electrons

You would need about 7350 electrons to equal the mass of a helium nucleus.


This is how to get the answer I just dont understand why the mass of an electron is 1/1837th the mass of a proton when in my book it says. and its 7000 because Its rounded to 1 sig fig
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Offline rabolisk

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Re: A helium nucleus has two protons and two neutrons.How many electrons would it ta
« Reply #10 on: January 31, 2011, 01:18:35 AM »
What does your book say that a mass of an electron is? If you go by 0.00055 amu, then 0.00055 / 1 = 1/1819, which is close to 1/1837.

If you're asking why an electron weighs that much less than a proton, the best answer is that it just is.
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