Help! A few chemistry questions?

3. An electrically neutral atom of oxygen has eight electrons. What other facts do you know for sure about this atom?

There are eight neutrons in the nucleus.

There are eight protons.

There is a charge of +8 on an atom of beryllium.

There is a charge of 8 on an atom of beryllium.

8. An atom of gallium has 31 protons and a mass number of 70. What is the atomic number for an atom of gallium?

31

35

39

70

9. Mercury has an atomic number of 80 and a mass number of 200. How many neutrons are in one atom of mercury?

40

80

120

200

Please explain how to do the last 2! Thank you!

Update:

THANK YOU sooo much guys!!!! one of u can answer my other one (its the exact same one) so i can give u both points!

please answer this one also!!:

http://uk.answers.yahoo.com/question/index;_ylt=Aj...

2 Answers

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  • 7 years ago
    Favorite Answer

    3) 8 protons because an electrically neutral atom would have equal number of protons and electrons.

    8) 31 because the atomic number is always the number of protons

    9) 120 because the protons plus the neutrons will give you the mass number of the atom. Proton and neutrons are roughly 1 AMU. As stated before, the atomic number is equal to the number of protons, so 200 minus 80 will give you the number of neutrons, 120.

    Source(s): My brain
  • Anonymous
    7 years ago

    3. It has eight protons (where did beryllium come form)

    4. 31, the atomic number is also known as the proton number, or the number of protons on atom has. This can not change. If you change the number of protons in an atom, it is no longer the same atom.

    5. 120

    Mass number = # protons + # neutrons

    200 = 80 + neutrons

    neutrons = 200 - 80 = 120

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