Final answer:
Iodine (I) can form a covalent bond with nitrogen because as a halogen, it has seven valence electrons and can share an electron with nitrogen to form a molecule like nitrogen triiodide (NI3).
Step-by-step explanation:
The element that can form a covalent (molecular) bond with nitrogen from the options provided is iodine (I). Sodium (Na) forms ionic bonds because it is a metal in Group 1 which tends to lose one electron to form a cation (Na+). Magnesium (Mg) also forms ionic bonds, as it is a metal in Group 2 and loses two electrons to form a Mg2+ ion. Neon (Ne) is a noble gas with a full valence shell, making it chemically inert and unable to form stable covalent or ionic bonds in normal conditions. Iodine (I), being a halogen in Group 17, has seven valence electrons and can share one electron with nitrogen to form a covalent bond, resulting in a molecule of nitrogen triiodide (NI3).
Nitrogen (N), being in Group 15, is a nonmetal and generally forms three covalent bonds to complete its octet, thereby achieving the electron configuration of the following noble gas, neon (Ne). Since iodine can share one electron with nitrogen, three iodine atoms can covalently bond with one nitrogen atom to form NI3.
To summarize, among the given options, only iodine has the capacity to form a covalent bond with nitrogen due to its position in the periodic table and its need to gain one electron to complete its valence shell, which complements the need for nitrogen to share three electrons to achieve stability.