Textbook 2B 9(b)

[506477319]

For the textbook problem 2B 9(b), it asks us to draw the lewis structure for potassium phosphide, which I searched up to be K3P. I have two questions:

1. are we expected to know that potassium phosphide is K3P, or would the test tell us the chemical formula?
2. how do we know this interaction between K and P are ionic bonds instead of covalent bonds? Is it because K is a metal? If yes, would metals always form ionic instead of covalent bonds and what about elements in the d orbital?

Thank you!

[Chem_Mod]

1. Yes, you should be able to figure out that potassium phosphide is K3P. I would recommend reviewing the common ion periodic trends, because they tell you that group 1 elements form +1 ions, while the first 4 elements of group 15 elements always form -3 ions.

2. The interaction between K (potassium) and P (phosphorus) is considered ionic because of the following key reasons. K is an alkali metal with a very low ionization energy, meaning it easily loses an electron to form K +. Metals in Groups 1 and 2 tend to form ionic bonds with nonmetals by transferring electrons (again, look at common ion periodic trends). P, being a nonmetal, has high electron affinity and readily accepts electrons to form P 3−. This electron transfer creates an electrostatic attraction between K + and P 3−, forming an ionic bond.


Do metals always form ionic bonds? Alkali and Alkaline Earth Metals (groups 1, 2) almost always form ionic bonds when reacting with nonmetals because they easily lose electrons (again, look at common ion periodic trends)