Atoms of most elements are less likely to react when they have A. 2 valence electrons
B. 4 valence electrons
C. 6 valence electrons
D. 8 valence electrons

Consider a system to be two train cars traveling toward each other. what is the total momentum of the system before the train cars collide?   kg • what must the total momentum of the system be after the train cars collide?   kg •