Why can only Nitrogen, Phosphorus, Arsenic and Carbon form triple bonds? Check all that apply.
Because they each have 5 valance electrons
Because they each have 6 valance electrons
Because they each have 7 valance electrons
Because they each have 4 valance electrons

The conventional answer is the “expanded octet because d-orbitals” explanation.

That explanation is wrong.

Explanation:

The reason that phosphorus can form “five bonds” and nitrogen only three or four has to do with the size of the two atoms. Phosphorus can fit five fluorine atoms around itself; nitrogen cannot. For specifics, see my answer to Do atoms always obtain 8 valence electrons in a covalent bond?

You should note that nitrogen has a perfectly accessible +5 oxidation state; that’s its oxidation state in nitrate, and you can model that as having five bonds to nitrogen just as easily as y

ou can model phosphate as having five bonds to phosphorus.

For a good digest of the controversy, with citations of the relevant primary literature, see Bill Jensen’s piece “The origin of the term ‘hypervalent’” in J. Chem. Educ. 2006, 83(12), 1751–2. DOI: 10.1021/ed083p1751

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na

Show an image of the data (˵¯͒ བ¯͒˵)