1. Hydrogen Molecule ($H_2$): Hydrogen has one valence electron. To achieve a stable duplet configuration, two hydrogen atoms share one pair of electrons.
$$\text{Bonds in } H-H = 1$$
2. Nitrogen Molecule ($N_2$): Nitrogen belongs to Group 15 and has five valence electrons. To achieve an octet, each nitrogen atom requires three more electrons. Thus, they share three pairs of electrons, forming a triple bond.
$$\text{Bonds in } N \equiv N = 3$$
3. Hydrogen Chloride ($HCl$): Hydrogen needs one electron to complete its duplet, and Chlorine (Group 17) needs one electron to complete its octet. They share one pair of electrons.
$$\text{Bonds in } H-Cl = 1\lt strong\gt 4. Total Calculation:\lt /strong\gt \text{Sum} = (\text{Bonds in } H_2) + (\text{Bonds in } N_2) + (\text{Bonds in } HCl)$$
$$\text{Sum} = 1 + 3 + 1 = 5$$
Therefore, the total sum of covalent bonds in these three molecules is 5.