How can you tell whether two atoms will form a covalent or ionic bond?
It’s all about electronegativity… hopefully you’re familiar with that idea. In a nutshell, electronegativity is the tendency of an atom to pull electrons toward itself when it forms a bond with another atom (kind of a tug-o-war between the atoms to get the electrons). An atom with a high electronegativity will have a strong pull. If two atoms have the same electronegativity, then they will share a pair of electrons equally…. a perfectly covalent bond. With different atoms, if the electronegativity difference is very large, one atom will take both electrons in the bond for itself. Effectively, the more electronegative element has taken an electron from the less electronegative atom… in other words, ions have been formed. So… similar electronegativities lead to covalent bonds (e.g. CO2, H2O) while very different electronegativities result in ionic compounds (e.g. NaCl). Practical outcome: The further apart elements are on the periodic table, the bigger the electronegativity diffe
