When most of the positively charged particles aimed at a piece of gold foil passed through it, but a few deflected or bounced back, Rutherford suggested that . an atom must consist of negative charges scattered throughout a ball of positive charge
electrons have almost no mass
electrons move in specific orbits around the nucleus of an atom
an atom’s positive charge must be clustered in a tiny region at its center

in the analysis of systems that involve fluid flow, we frequently encounter the combination of properties u and pv.

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.