The sugar and phosphate in DNA are connected by covalent bonds. A covalent bond is formed when atoms share electrons. It is very common for atoms to share pairs of electrons. An ionic bond is created when one or more electrons are transferred between atoms. Ionic bonds, also known as electrovalent bonds, are formed between ions with opposite charges. There is no such thing as an overt bond in chemistry. The exam will require you to understand and have some examples of these different types of bonds.