Baking soda is a perfectly safe way to naturally whiten your teeth but if you use the baking soda too much on your teeth it can erode away the natural enamel that protects your teeth.
I brush my teeth 4 times per week with baking soda paste that I make by mixing it with water with baking soda and then brush my teeth normally like I would with toothpaste and it keeps my teeth white and has whitened my teeth as well.
Then the rest of the days of the week I brush my teeth with normal toothpaste with fluoride to keep my teeth healthy and strong.