What combination of elements typically forms a molecular compound?
To be more accurate, all bonds have an "ionic character" - this can be described by calculating the difference in electronegativities between the two elements.
When the difference is zero (ie. element boded to another identical element) it would have essenetially zero ionic character.
When the difference is between 0 and 0.4 we typically refer to this as a non-polar covalent molecular bond - the electrons are shared relatively evenly and do no create a significant dipole moment.
When the difference is between 0.4 and 1.7, a strong ionic character is developing in which partial charges begin to form on their respective atoms (the more electronegative element becomes slightly negative, & vice versa). This bond is called a Polar Covalent Molecular Bond
When the difference in electronegativity exceed 1.7, the shared electron pair has essentially migrated to the more electronegative element, creating an ions
Nonmetals generally have electronegativites that are fairly similar, so their differences fall in the covalent molecular bond category as a general rule.