# The Atom & the Periodic Table. Reading the Periodic Table.

## Presentation on theme: "The Atom & the Periodic Table. Reading the Periodic Table."— Presentation transcript:

The Atom & the Periodic Table

Atomic Number = Number of protons in the nucleus

Reading the Periodic Table Atomic Number = Number of protons in the nucleus Average Atomic Mass = Average Mass of the atom in units of amu, or just u)

Reading the Periodic Table Atomic Number = Number of protons in the nucleus Average Atomic Mass = Average Mass of the atom in units of amu, or just u) Why “Average” Atomic Mass? Some atoms of an element have a different mass than others because they have more or fewer neutrons. These are called Isotopes.

Reading the Periodic Table Atomic Number = Number of protons in the nucleus Average Atomic Mass = Average Mass of the atom in units of amu, or just u) Why “Average” Atomic Mass? Some atoms of an element have a different mass than others because they have more or fewer neutrons. These are called Isotopes. Certain isotopes, such as Carbon-14, are useful for dating substances because their rate of radioactive decay is known.

Reading the Periodic Table Atomic Number = Number of protons in the nucleus Average Atomic Mass = Average Mass of the atom in units of amu, or just u) Why “Average” Atomic Mass? Some atoms of an element have a different mass than others because they have more or fewer neutrons. These are called Isotopes. Certain isotopes, such as Carbon-14, are useful for dating substances because their rate of radioactive decay is known. 14 is the Mass Number for Carbon-14. The mass number represents the total number of protons plus neutrons in an isotope of an element. C-14 has 6 protons and 8 neutrons.

Reading the Periodic Table Atomic Number = Number of protons in the nucleus. Average Atomic Mass = Average Mass of the atom in units of amu, or just u. Why “Average” Atomic Mass? Some atoms of an element have a different mass than others because they have more or fewer neutrons. These are called Isotopes. Certain isotopes, such as Carbon-14, are useful for dating substances because their rate of radioactive decay is known. amu (Atomic Mass Unit) = 1/12 the mass of Carbon-12. Carbon-12 has 6 protons and 6 neutrons. Carbon 12 weighs 12 amu. Therefore, protons and neutrons have a mass of roughly 1 amu. 14 is the Mass Number for Carbon-14. The mass number represents the total number of protons plus neutrons in an isotope of an element. C-14 has 6 protons and 8 neutrons.