1. Chapter 3 Isotopes Part II

2. Atoms Nucleus is center core. Nucleus is center core. Nucleus is made of Protons & Neutrons. Nucleus is made of Protons & Neutrons. Electrons orbit the nucleus. Electrons orbit the nucleus.

3. Atomic Number The Atomic Number is the number of protons found in the nucleus. All atoms of an element have the same Atomic Number

4. Mass Number Mass number is the number of neutrons and protons in the nucleus. Mass number is the number of neutrons and protons in the nucleus. This number is not always the same for all atoms in an element. This number is not always the same for all atoms in an element.

5. Isotopes

6. Isotopes Isotopes of an element have the same number of protons but different numbers of neutrons. Isotopes of an element have the same number of protons but different numbers of neutrons. The charge is the same, but they have a different mass. The charge is the same, but they have a different mass.

7. But how it that different from Atomic Mass? Atomic mass takes into account the relative abundance of each isotope. Atomic mass takes into account the relative abundance of each isotope. The weight of atoms are measured in amu’s The weight of atoms are measured in amu’s

8. What is an amu? Amu is Atomic Mass Unit. Amu is Atomic Mass Unit. It is defined as 1/12 th of the mass of a Carbon-12 atom. It is defined as 1/12 th of the mass of a Carbon-12 atom.

9. Relative abundance Most elements have one isotope that is the majority share of the element. Most elements have one isotope that is the majority share of the element.

10. Calculating the Atomic Mass from the sum of the isotopes. The atomic mass takes the natural abundance into consideration. The atomic mass takes the natural abundance into consideration. Assume the sample is 1 gram. Assume the sample is 1 gram. 99.985% of 1.007825035 is 1.007673861 99.985% of 1.007825035 is 1.007673861 0.015% of 2.014101779 is 3.02115 x10 -4 0.015% of 2.014101779 is 3.02115 x10 -4 The sum of these is the atomic mass: The sum of these is the atomic mass: 1.007975976 amu 1.007975976 amu

11. Worksheet