We present in this work a new simple estimation of Stark broadening of neutral atoms in plasmas. This is achieved by exploiting the S-matrix unitarity criteria to get a more precise estimation of the minimum of the impact parameter. The latter depends on a critical velocity of the free electrons. The result is: the collision operator is the sum of two contributions; the first is from electrons velocities less than the critical velocity (slow electrons), and the second is from electrons with velocities greater than the critical velocity (fast electrons). When the reduced critical velocity is very small (vc≪1), it is shown that the strong collision contribution can be expressed by Meijer G-functions. This corresponds to high energy ionization element in stellar plasmas. Then we applied our theoretical results to a plasma consisting of magnesium. We find a good agreement with experimental and with others theoretical results for a range of electron densities and temperatures.