Question

An element in the periodic table has the electronic configuration of 2, 8, 7. Which of the following family does the element belong to?

• A. Alkali metals
• B. Alkaline earth metals
• C. Noble gas
• D. Halogens

Answer 1

The correct option is D Halogens

From the electronic configuration, it is clear that the last shell has 7 electrons. The rule to find the group number from the number of electrons in the last shell is as follows:

1) If the number of last shell electrons is 1 or 2 then the group number is also 1 and 2 respectively.

2) If the number of last shell electrons is more than 2, then the group number = Number of electrons in last shell + 10

Since the element given to us has 7 electrons in the last shell. So the group number for this element is

Group number = 7 + 10

Group number = 17

So the group number of this element is 17 which is the halogen family in the periodic table.