Element a has a half-life of 10 days. a scientist measures out 200 g of this substance. after 30 days has passed, the scientist reexamines the sample.
how much element a will remain in the sample?
50 g
25 g
12.5 g
100 g

In this synthesis reaction what products will form

When balancing a chemical equation:

Great amounts of electromagnetic energy from our sun and other bodies in space travel through space. which is a logical conclusion about these electromagnetic waves? their energy must be very their frequency must be very low these waves can travel without a medium they only travel through a vacuum of space