Thank you for the opportunity to help you with your question!
"Periods" on the periodic table of elements just means to look at the horizontal rows. Which of these elements is in the 6th row? Count 6 rows down and look all the way across the 6th row. At is in the 6th row, or period.
Please let me know if you need any clarification. I'm always happy to answer your questions.
Oct 21st, 2015
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