7. The organization of the periodic table is based on the properties of the elements and reflects the structure of atoms. As a basis for understanding this concept:
a. Students know how to identify regions corresponding to metals, nonmetals, and inert gases.
b. Students know each element has a specific number of protons in the nucleus (the atomic number) and each isotope of the element has a different but specific number of neutrons in the nucleus.
c. Students know substances can be classified by their properties, including their melting temperature, density, hardness, and thermal and electrical conductivity.