Sedimentation is least likely to occur: on a mountainside in a lake on a sandbar in a sand dune

 On a Mountainside.

Explanation: Sedimentation is less likely on  a mountainside, since due to the inclination that it presents, it is most likely that the materials that are released from them by natural agents such as wind or rain, go to more places lows such as rivers, lakes, or flat surfaces where sediments will accumulate and form.

because the two particles have an equal charge, the charges will cancel out and give the atom an overall charge of 0. so, if at atom has 35 protons in the nucleus, we could expect it to have 35 electrons orbiting that nucleus.