Why is the script not working?

Players = game:GetService("Players")

function onPlayerAdded(player)
    while wait(.1) do
        local RPart = Instance.new("Part")
        local RPosition = player.Head.Position
        RPart.Position = RPosition
        RPart.BrickColor = BrickColor.new("Green")
        repeat until 1 == 2
    end
end

game.Players.PlayerAdded:connect(onPlayerAdded)

for _,player in pairs(Players:GetPlayers()) do
    onPlayerAdded(player)
end

It said: "13:06:50.064 - Head is not a valid member of Player".