Explanation:
Pure subsance is a substance that is made up of only one type of particle - each piece is the same throughout.
Being present before the reaction but not after means it's no the same (it couldve evaporated)
Answer:-
Metalloids
Explanation:-
The stair step line is a line in the periodic table that divides the metals on one side and the non metals on the other side. So the elements which lie on the stair step line must have properties in between those exhibited by the metals and those by the non metals.
Such elements we know are called metalloids. Thus In the periodic table, the elements that are adjacent to the "stair step" are called metalloids.
The answer would be D. This is because sulfur is on it's own, meaning one. while tri is a prefix for three so there are three oxygen atoms.
