Why do most objects tend to contain nearly equal numbers of positive and negative charges?

Which of the following are considered noble gases? a. bromine b. neon c. argon d. chlorine

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.

Why do atoms emit energy of only specific wavelengths