Who first proposed that matter is composed of tiny, indivisible particles?

What is the number of moles of chemical units represented by 9.03x10^24? and how do i show work? (dumb it down )

Acontrol during an experiment. might change remains constant does not exist does change

13. a covalent bond between two atoms is likely to be polar if: a. one of the atoms is much more electronegative than the other. b. the two atoms are equally electronegative. c. the two atoms are of the same element. d. the bond is part of a tetrahedrally shaped molecule. e. one atom is an anion.