Which of the following is true about compounds?' O They are physical combinations
O They have compositions that vary.
O They are pure substances.
O They have properties similar to those of their component elements.

How many moles of air are there in a human lung with a volume of 2.4 l at stp? explain your answer

How far is the region from the equator or control climate

Question 3(multiple choice worth 4 points) (04.04 lc) what does it mean when an element is reduced? it empties a valance shell, reducing its atomic radius. it gains electrons, reducing its overall charge. it increases electronegativity, reducing its ability to bond. it loses electrons, reducing its electron number.