When I studied physics and chemistry in school I was taught that atoms are composed of protons, nuetrons, and electrons, and that their interactions can explain chemistry and chemical interactions. Now I understand that this is either wildly oversimplified or wildly out of date. Would somebody be able to catch me up, simply, on what the smallest building blocks of out world are and how they interact to create matter?
In: Physics
For chemistry:
Protons are positively charged and electrons are negatively charged. For chemical reactions, the neutrons don’t matter because they have no charge. Neutrons act like glue to help hold the nucleus together, but they don’t affect reactions with other atoms. Isotopes – elements with the same number of protons but different numbers of neutrons – are *chemically* identical.
Atoms “want” to be electrically neutral. If there are more protons than electrons, the atom will be positively charged and will attract negatively charged electrons until it captures an electron and becomes neutral. If there are more electrons than protons, it will have an overall negative charge and the outermost electrons will be repelled until one manages to escape, so the atom is neutral.
Atoms also want to have completely full (or completely empty) outer electron shells, due to quantum mechanics things. Of course, an atom can’t merely add or subtract electrons because then it would become electrically unbalanced. So, atoms share electrons. Take water: oxygen has six electrons in the outer shell, but eight would make it full. Hydrogen has one in its outer shell, and two would make it full. So, one oxygen atom shares two of its electrons with two hydrogen atoms, which each share their one. All of the atoms get a full outer shell *and* the number of protons and neutrons in the entire molecule add up to be electrically neutral.
If an atom is very close to being very full or very empty, it may be more stable if it does become electrically neutral. These atoms don’t share electrons, they just either take them or give them away and become *ionized*, meaning they have an electric charge. Ions with opposite charges will attract each other and stick together. This is how table salt works: sodium has one extra electron in its outer shell, and chlorine is missing one. The sodium atom gives up its electron and becomes positively charged, and the chlorine atom takes the electron and becomes negatively charged. The positive sodium and negative chlorine stick together as sodium chloride, which is table salt.
Metals tend to have loosely bound outer electrons and they share all of them in a sort of “sea” of loose electrons that bounce around between nuclei. That’s why metals are usually very good conductors.
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