Answer:
element
Explanation:
An element is a pure substance that cannot be separated into simpler substances by chemical or physical means. • There are about 117 elements.
The element calcium has a total of four energy levels<span> that each can hold a certain number of electrons. Its first and fourth energy levels hold two electrons each, and its second and third energy levels hold eight electrons each.</span>
Answer:
6s
Explanation:
Barium is in group 2 of the s block and is in period 6.
