Why were there only 2 categories (plants and animals) when the classification system was first introduced

Which of the following is not a characteristic of a hydrogen bond? 1. it is responsible for the unusual physical properties of water. 2. it is weaker than a covalent bond. 3. it is stronger than other dipole-dipole interactions. 4. it can occur when hydrogen is covalently bound to very electronegative elements liks f, cl, br and i.

Me soon im confused much mass would a mole of hydrogen molecules contain? recall that hydrogen is diatomic. g/mol

Which of the following pairs of elements is most likely to form an ionic compound? a oxygen and fluorine b sodium and aluminum c calcium and chlorine d nitrogen and sulfur