Answer to Question #131838 in Inorganic Chemistry for Morgan

Question

Na and K belong to group 1 in the periodic table of elements.

(a) Explain why, in terms of their electronic configurations, potassium is more reactive than sodium.

(b) Write the balanced equation for the reaction of sodium with water.

Answer 1

(a) Sodium electron configuration is 1s²2s²2p⁶3s¹. Potassium has the electron configuration 1s²2s²2p⁶3s²3p⁶4s¹ rather than the expected 1s²2s²2p⁶3s²3p⁶3d¹. Potassium has a larger average atomic radius (220 pm) than sodium does (180 pm). The potassium atom has an extra electron shell compared to the sodium atom, which means its valence electrons are further from the nucleus, giving potassium a larger atomic radius. Potassium valence electron is at a greater distance from the attractive nucleus and is so removed more easily than sodium valence electron. As it is removed more easily, it requires less energy, and can be said to be more reactive.

(b) 2Na + 2H₂O → 2NaOH + H₂