Neutral fractions of scattered ground-state hydrogen atoms after grazing incidence collisions of both H(1s) and H+ projectiles with an Al(111) surface have been computed within the impact velocity range 0.1 <= v <= 2.0 a.u. by means of the ETISC1D code. Comparison between the results related to the H(1s) beam with those obtained for H+ projectiles-which we found in earlier work to be in good agreement with experimental data-shows that in the velocity range 0.3 <= v <= 1.3 a.u. neutral fractions keep the memory of the initial state, whereas in the extreme ranges of low velocities (v less than or similar to 0.3 a. u.) and high velocities (v greater than or similar to 1.3 a. u.), the outgoing charge fractions do not depend on the charge state of the initial beam. In order to analyze qualitatively these findings, rate-equations calculations as well as a simplified analytical model have been also implemented. Due to the lack of experimental data for impinging H(1s), the present results represent important theoretical predictions which might stimulate further experimental works.