 While H2 is not very reactive under standard conditions , it does form compounds with most elements . Hydrogen can form compounds with elements that are more electronegative , such as halogens ( e.g. , F , Cl , Br , I ) , or oxygen ; in these compounds hydrogen takes on a partial positive charge . When bonded to fluorine , oxygen , or nitrogen , hydrogen can participate in a form of medium @-@ strength noncovalent bonding with the hydrogen of other similar molecules , a phenomenon called hydrogen bonding that is critical to the stability of many biological molecules . Hydrogen also forms compounds with less electronegative elements , such as metals and metalloids , where it takes on a partial negative charge . These compounds are often known as hydrides . 
