How can you tell if something is an ionic or covalent bond just by looking at the formula: NaCl, H20, etc...?

Answer 1

generally speaking

metal + non-metal = ionic

non-metal + non-metal = covalent

If you have learned about electronegativity differences, then you can also use that, but you said just by looking

Since Na is a metal and Cl is a non-metal = ionic

Since H is a non-meta and O is a non-metal - covalent

Answer 2

This is an inexact part of chemistry unless you are given electronegativity values. However, here is a brief summary:

A compound will likely contain an ionic bond if the elements are on opposite ends of the periodic table. Ionic bonding involves elements giving up and taking electrons; elements on the left side of the table want to give them up, elements on the right want to take them. To use your example, NaCl is ionic, because Na is group 1, and Cl is group 7.

A compound will have a covalent bond if the elements are relatively close to each other in the periodic table. This is because they will want to take electrons an equal amount; they share the electrons in a covalent bond. H2O contains covalent bonds, because hydrogen is effectively group 7, and oxygen is group 6.

I hope this helps.

Answer 3

It is generally done by evaluating the difference in electronegativity; molecules with large electronegativity differences of the component atoms are generally ionic. You would need to look up the values untill you are sufficiently familiar with them that you could do it by looking at the formula.

Answer 4

Usually the combination of a metal and a nonmetal is a ionic bond. A combination of two nonmetals will not dissociate.