The group number, number of valence electrons, and valency of an element with the atomicnumber 15, respectively, are:(a) 16, 5 and 2 (b) 15, 5 and 3 (c) 16, 6 and 3 (d) 15, 6 and 2

To determine the group number, number of valence electrons, and valency of an element with the atomic number 15, we can refer to the periodic table.

Step 1: Find the element with atomic number 15. Looking at the periodic table, we find that the element with atomic number 15 is phosphorus (P).

Step 2: Determine the group number. The group number of an element indicates the number of valence electrons it has. In the case of phosphorus, it is located in group 15. Therefore, the group number is 15.

Step 3: Determine the number of valence electrons. Since phosphorus is in group 15, it has 5 valence electrons.

Step 4: Determine the valency. The valency of an element is determined by the number of electrons it gains, loses, or shares to achieve a stable electron configuration. For phosphorus, it tends to gain 3 electrons to achieve a stable configuration. Therefore, the valency of phosphorus is 3.

So, the correct answer is (d) 15, 5, and 3.