Structure of an Atom | Best Biology Review
Structure of Atoms
A neutral atom consists of an extremely dense nucleus. We see this nucleus right here. It’s going to be composed of one or more positively charged protons. I’m just going to draw a circle right here and put a P in the middle. That’s going to stand for “proton”. This middle circle here represents the nucleus. It’s going to be really dense. It’s made up of these positively charged protons.
Then, inside this nucleus, there’s also going to be a varying number of uncharged neutrons. That exists in every atom except for hydrogen 1. I’m going to go ahead and draw some more circles and we are put an N in there for “neutron”. Notice they’re connected to the protons. Now, there’s going to be a cloud of one or more negatively charged electrons outside of the nucleus.
The number of electrons is going to be equal to the number of protons. I’m going to draw some circles with an E in them to represent electrons. We have three protons in there, so there are going to be three electrons. Now, say there are four protons, then there’s going to be four electrons out here. There’s a bond between the protons and neutrons. They are bound together by a strong nuclear force.
This force is stronger than the repulsive force between the positively charged protons. All these protons are positively charged. I’m going to put a plus symbol. Positive charges, or like charges, want to repel away from each other. But the bond between the neutrons and the protons are stronger than the repulsive force between the protons. Neutrons, by the way, have no charge. They’re not positive or negative.
They’re uncharged. Now, the negatively charged electrons, which are out here, these are negatively charged, so I’m going to put negative symbols. These negatively charged electrons are attracted to the positively charged protons by the electromagnetic force. All of these electrons are attracted to the protons that are inside. Remember, earlier I said there has to be the same number of protons as there is electrons.
The reason for that is because this is a neutral atom, meaning it has no charge. The four positive charges that we have here cancel out the four negative charges we have. Say we had four positive charges and we had seven negative charges. Overall, this atom would have an overall negative charge. That’s not the case, because there’s the same amount of positive and negative charges. The atom as a whole is neutral.
Now, the number of protons determines the identity of the chemical element, while the number of electrons in the outermost shell determines the ways in which the atom interacts chemically with other atoms or molecules. This is the shell right here outside the nucleus. Sometimes there are other shells. In this case there is just one. The number of electrons in this outermost shell determines the ways in which the atom interacts chemically with other atoms or molecules.
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Last updated: 10/23/2018