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.
Best Answer: The period number is a just a fancy name of saying which horizontal row an element appears in on the periodic table. The first row, hydrogen and helium, appears at the top of the periodic table. Altogether, there are 7 rows (horizontally on the table). The atomic number is how many protons ab atom/ion of that element has.