Final answer:
To order atoms by their covalent bonding capacity, hydrogen forms one bond, oxygen two, nitrogen three, and carbon four, based on their need to complete their valence electron shell or achieve an octet.
Step-by-step explanation:
When ordering atoms by the number of covalent bonds they could form from least to most, we look at their need to achieve an octet or, in the case of hydrogen, a duet of electrons. Hydrogen (H) with an atomic number of 1 has one valence electron and only needs one more electron to achieve a full shell, thus it forms one bond. Oxygen (O) with an atomic number of 8 has six valence electrons and needs two more, so it forms two bonds. Nitrogen (N) with an atomic number of 7 has five valence electrons and needs three more, forming three bonds. Carbon (C), with an atomic number of 6, has four valence electrons and requires four additional electrons to complete its octet, hence it forms four bonds. Therefore, the order from least to most covalent bonds formed is: Hydrogen, Oxygen, Nitrogen, and Carbon.