In the periodic table of elements, some elements share similar properties and have the same number of valence electrons in their outer shell. what do we call these type of elements in the periodic table of elements.

Why do cells appear different in distilled water than they do in 10% salt water?

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

The biosphere of the earth is made up of what compound? organic or inorganic?