The density of copper is 8.94g/cm3 at 20°C and 8.91g/cm3 at 60°C. This density decrease is the result of which of the following ? State by inserting true or false and give an explanation. a) the metal expand
b) the metal contrast
c) the mass of the metal increase
d) the mass
of the metal decrease

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.

the answer is d.) potassium