And the service in these stores is also very good. Generally, the price of an eye exam in Wal-mart, Costco and Target optical can range from less than $50 (if you have an eye exam at a retail store or optical chain) to $100 or more (if you have an eye exam at a medical clinic or private eye doctor's office).
What is true about the elements of a period? (Select all that apply.) a.They have the same number of electron shells. b They have similar chemical characteristics. c They have similar physical characteristics.
The second period contains the elements lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon. This situation can be explained by modern theories of atomic structure. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the 2s and 2p orbitals.