Isotopes and Mass Number. Leon the Electron. Jimmy Neutron. Atomic Number. The number of protons in each atom identifies it as an atom of a particular element Each atom has a unique number of protons and, in effect, the number of protons cannot change for a particular atom
Leon the Electron
Determining the State of Matter of a Particular Element Using the Periodic Table
The order of the elements on the Periodic Table is based on the number of protons in the nucleus.
Protons are the only thing in an atom that does not change.
How many protons does Platinum have?
How many neutrons does Mercury have?
How many electrons does Lead have?
What similarities do these three elements share?
The number of protons in the nucleus is called the atomic number. Also since the positive charges must equal the negative charges to have a neutral atom, and all atoms are neutral, the atomic number will also equal the number of electrons in an atom.
What is the atomic number of
What is the element?
Don't be an isodope, learn about an isotope.
All atoms of a particular element
have the same number of
protons and electrons
The number of neutrons may
In nature most elements are
found as a mixture of isotopes
Mass number = top
Atomic number = bottom
# neutrons = mass # - atomic #
Atomic mass: 34.969 amu Atomic mass: 36.966 amu
Percent abundance:75.770% % abundance: 24.230%
Mass Contribution: Mass Contribution:
(34.969)(.75770)= 26.496 amu (36.966)(.24230)=8.957 amu
Weighted average atomic mass of chlorine =
(26.496 amu + 8.957 amu) = 35.453 amu
1. Turn the % into a decimal for the % abundance.
2. Multiply the decimal by the atomic mass of each particular isotope.
3. Add the masses of the isotopes together.
4. Your answer will be in amu’s (atomic mass units).
Calculate the atomic mass of Magnesium. The three Magnesium isotopes have atomic masses and relative abundances of 23.985 amu (79.99%), 24.986 amu (10.00%), and 25.982 amu (11.01%).
1. What is the atomic mass of this sample of Silver?
107 Ag 106.905 amu 52 %
109 Ag 108.905 amu 48 %
2. What is the average atomic mass of this sample of Hydrogen?
1H 12 %
2H 48 %
3H 40 %
3. Boron has two naturally occurring isotopes, Boron-10 (abundance 19.8%, mass = 10.013 amu, Boron –11 ( abundance 80.2%, mass = 11.009 amu). Calculate the average atomic mass of Boron.