How do I describe the structure of compounds when just given the chemical formula?
KF will have an ionic bond and the Lewis structure would show the F with 8 electrons around it and the K with no electrons. The crystalline structure should be similar to that shown for NaCl. HF is however a molecular compound so the Lewis structure would show HF with a shared pair of electrons between the two atoms and the remaining 6 electrons around the F atom. The H atom thus has 2 electrons in its outer energy level (the max of 2 it can have) and F has the use of all 8 electrons to fill its outer energy level (the max of 8 it can have).
