The atomic mass of an element is the weighted average of the masses of… 1) its two most abundant isotopes
2) its two least abundant isotopes
3) all of its naturally occurring isotopes
4) all of its radioactive isotopes

h let me think

both adhesion and cohesion are attractions.

they are different in that adhesion is the force of attraction between the molecules of two different substances, whereas cohesion is the force of attraction between molecules of the same substance.

possible examples include capillary action, in which the adhesion between water and glass causes the water to rise in a narrow tube against the force of gravity.

because of hydrogen bonding, water is extremely cohesive.

this causes molecules on the surface of water to be drawn inward, which is why drops of water form beads on smooth surfaces.

hope this .

since electrons are negative the answer is neagtaive