The mass number of an atom is determined by ___. 1.adding the protons and electrons
2.adding the protons and neutrons
3.adding the electrons and neutrons
4. adding the protons, electrons and neutrons

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

what is the average time it took the car to travel 0.25 meters?

⇒ 2.23 seconds

what is the average time it took the car to travel 0.50 meters?

⇒ 3.13 seconds