How are the elements atomic numbers used to arrange them on the periodic table?
Elements are arranged by a successive increase in atomic number (i.e., the number of protons in the nucleus) as one moves across each row from left to right. This number uniquely identifies each element. • What is the general relationship between the atomic number and the atomic mass weight? For most elements, the atomic mass is double the atomic number. For elements such as tin, the atomic mass is slightly more than double the atomic number. This is because atomic weight is an average weight of all the isotopes of an element, and an element’s isotopes have different numbers of neutrons. • How might isotopes of an element differ from each other? An element’s isotopes have different numbers of neutrons. In addition, some isotopes are more stable than others. After Watching • Model the size of an atom. Divide the class into pairs or teams, and provide each one with a coin—a penny, dime, nickel, or quarter. Different teams can have different coins. Tell students that the diameter of the n
