There are different kinds of bonds that can form in a molecule. When two atoms approach each other close enough for their electron clods to interact, the electrons of one repels the electrons in the other, and the same thing happens within the nucleus of the atoms. At the same time, each atom’s negatively charged electron is attracted to the other atom’s positively charged nucleus. If the atoms still come closer, the attractive forces offset the repulsive and the energy of the atom decreases and bonds are formed – the atom sticks together. When the energy decrease is small, the bonds are van der Waals. When the energy decrease is larger, we have chemical bonds, either ionic or covalent.


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Ionic bonds generally involve metals from the left side of the periodic table that interact with nonmetals from the far right side. Look at your periodic table now – do you see the atoms near the rare gases? Those usually form ions. Covalent bonds form when elements lie closer to one anther in the periodic table. Most chemical bonds are somewhere between purely ionic and purely covalent.


Ionic compounds aren’t really real molecules. When ionic compounds are solids, they are really a structure of charged particles. When one atom accepts or donates an electron to another atom, an ionic bond is formed, like in table salt (NaCl). Do you see how there’s only 1 electron in sodium in the outermost shell? And notice how chlorine has seven, not 8 in the outermost shell? Chlorine wants to feel full (8), and sodium has only 1 out of the 8, so it donates it to chlorine. Not all atoms hold onto their valence electrons with equal strength.


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