Which pair of elements has the most similar properties? a. k and heb. li and bc. i and ca d. n and p

Option d: N and P

In a periodic table, elements within the same group have similar properties.

(a) K and He: Here, K (potassium) belongs to group 1 , alkali metals and He belongs to group 18, noble gas thus, they cannot have similar properties.

(b) Li and B: Here, Li (lithium) belongs to group 1, alkali metals and B (boron) belongs to group 13, it is the only non-metal in group 13. Thus, they cannot have similar properties.

(c) I and Ca: Here, I (iodine) belongs to group 17, halogen, they electronegative in nature and Ca (calcium) belongs to group 2, alkaline earth metal, they are electropositive in nature. Thus, they cannot have similar properties.

(d) N and P: Here, both N (nitrogen) and P (phosphorus) belongs to group 15, they both are non metals and have 5 electrons in their outermost shell thus, they both have similar properties.

Therefore, option (d) is correct.

lithosphere and asthenosphere

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.