What is a simple definition of atomic mass???

Question

I actually do well in science, but I am just looking for a straight definition. How do you calculate/find it? And if possible, would you please use it in a context sentence? Thank you for your time.

Answer 1

Would this help?

http://www.answers.com/atomic+mass&r=67

Answer 2

The mass of an atom, usually expressed in atomic mass units

mass - the property of a body that causes it to have weight in a gravitational field

Calculating Atomic Masses



3

Li

6.94





Atomic number (number of protons)



Atomic mass (weighted average)

a.         The periodic table lists atomic masses for each element.

b.         The atomic mass is not a whole number because it is the weighted average of the masses of the different isotopes of that element.

c.         Atomic masses do not always increase directly with relation to atomic number. See the exceptions for Co and Ni; Cu and Te; and Te, I and Xe.



Example 1        An element has two isotopes: one of mass 63 u; the other with a mass of 65 u.

If the relative abundance of the isotopes is 69.1% and 30.9 %, respectively, find the atomic mass of the element.



Answer:

                        First convert percents to decimals out of 1. Then, multiply each mass by their relative abundance and add them up:

                        the weighted average = atomic mass = 0.691(63) + 0.309(65) = 63.6 units



Example 2        If the relative abundance of a neon isotope was 5.7%, and the rest was only Ne-20, what was the mass number of the minor isotope?



                        Answer:



                        The rest = 100% - 5.7% = 94.3% = mass of 20

                        Unknown mass = 5.7%.

                        Periodic table reveals the weighted average to be 20.18 units, so



                        0.943(20) + 0.057x = 20.18

                        x = 23.1, so the mass number of the other isotope is about 23.

hope this helps ....enjoy

Answer 3

"Atomic Mass" is most easily described as "the mass of one atom of an element"

Therefore, if you have an atom of Hydrogen, you've got 1 proton and 1 electron. The proton weighs:

proton mass = 1.67262158 × 10-27 kilograms

...according to Google's converter.

The mass of an electron is pretty much negligable.

The masses listed on the Periodic Table are values for 1 mole of an element. So, we'd expect 1.6726E-27 kg X 6.02E23 (avogadro's #) to be about 1.008... Which it is.

One thing to be careful about, masses of in the nucleus DO NOT add like you think they would, there is some 'nuclear loss'. That's why its so convenient to refer to the number on the Periodic Table.

I hope that answers your question.