# Question Video: Understanding the Properties of Atoms Physics

If a neutral atom has 12 protons in its nucleus, how many electrons does it have?

02:06

### Video Transcript

If a neutral atom has 12 protons in its nucleus, how many electrons does it have?

To figure out the answer of this question, let’s recall the basic structure of an atom. Every atom has a nucleus made up of some number of protons and neutrons. And that nucleus is surrounded by orbiting electrons. In this question, we’re told that we have a neutral atom that has 12 protons in its nucleus. If we consider the protons to be these rose-colored spheres in our nucleus, then we can count one, two, three, four, five, six, seven, eight, nine, 10, 11, 12 of them. For this atom to be considered a neutral atom as it is, that means the charge of these protons must be balanced out by the charge of the orbiting electrons. We can recall then what the relative charge of a proton is and what the relative charge of an electron is.

Now, independent of one another, a proton does have a specific amount of electric charge, and so does an electron. But in this case, we’re not concerned with that specific amount, but rather just how the charges compare to one another. From that perspective, we can recall that the charge of a proton is equal and opposite the charge of an electron. So if we let the relative charge of a proton be plus one, then the relative charge of an electron would be negative one. This tells us that if we add together a proton and an electron, the combined electric charge of that combination is zero. In other words, together, the particles are overall electrically neutral. That helps us figure out the answer to our question, which asks, how many electrons does this neutral atom with 12 protons have?

If the charge of one electron effectively cancels out the charge of one proton, then that must mean our neutral atom has the same number of protons as electrons. We have 12 protons in our nuclear core. And right now, we have one, two, three, four, five, six, seven, eight, nine electrons. We’ll need to add three more to this picture so that the total negative charge, negative 12, balances out the total positive charge of positive 12. And this then tells us our answer. We need to have 12 electrons for this to be a neutral atom. That’s how many will balance out the charge of the 12 protons in the nucleus.