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.
Periods on the Periodic Table. The rows on the periodic table are called periods. All the elements in a period have valence electrons in the same shell. The number of valence electrons increases from left to right in the period. When the shell is full, a new row is started and the process repeats. Groups on the Periodic Table