One quick physical science question

1. why isn’t it possible for an atom to have a mass number of 15 and an atomic number of 18?

In the context of the neural impulse, which of the following is true about the depolarization of neuron membranes?

What’s the student’s scientific question

Which statement is true for bacteria a. bacteria have complex internal structures b. all bacteria are spiral in shape c. all bacteria cause disease in animals d. bacteria break down some foods