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.
Classify each statement as true or false. 1. Period 4 elements have an inner electron configuration of Ar. 2. Group 8A elements have full outer principle s and p subshells. 3 Period 5 elements have an inner electron configuration of Xe. 4. The highest principle quantum number of period 3 elements is 4. 5. Period 3 elements have six 2p electrons. 6. The valence electrons of group 2A elements are in an s subshell. 7. The valence electrons of group 5A elemnts are in the 6s subshell. 8. The highest principle quantum number of period 2 elements is 2.