Why do most mass numbers on the periodic table have a decimal?

This image is an example of a(n) a) atom. b) compound. c) mixture. d) molecule.

How can parts of a solution be separated by chromatography?

An engineer decides to use a slightly weaker material rather than a stronger material, since she knows that the stronger material can break suddenly. this is an example of what? a choosing a material that will show warning before it fails b using composite materials that combine strength c using a material for multiple applications d using design techniques that increase efficiency and reduce cost