The atomic number of the element fluorine is 9. The isotope Fluorine-18 has a mass of 18 and fluorine-19 has a mass of 19. What is the reason for their mass differences?

Atomic mass is made up by the electrons protons and neutrons in an element. The reason for the mass differences are because of the varying number of electrons.

label a cell membrane

label b cytoplasm

label c ribosomes

label d dna

the membrane forms the outside of the cell

cytoplasm is the liquid within

ribosomes are the components within that distribute rna

the dna is the genetic make-up