Question

Which of the following pairs of elements and valence electrons is incorrect?

(3pts)
Question 12 - Which of the following pairs of elements and valence electrons is incorrect?

Br - 7

S - 4

Al - 3

Sr - 2

Answer 1

In the given pairs of elements and valence electrons, S-4 is incorrect.

• Valence electrons are the outermost electrons of any element.
• They occupy space in the last shell of the atom.
• Valence electrons can be easily found by using electronic configuration.
• In the Case of Bromine (Br), the atomic number of bromine is 35. The electronic configuration is 2,8,8,8,7. As we can see in the last shell 7 electrons are there, so valence electrons in Br are 7 which is correctly given.
• In the case of Sulphur (S), the atomic number is 16. The electronic configuration is 2,8,6. The last shell i.e. M shell contains 6 electrons, so there are 6 valence electrons in the sulphur which is incorrectly given.
• In the case of Aluminium (Al), the atomic number is 13. The electronic configuration is 2,8,3. The last shell i.e. M shell contains 3 electrons, so there are 3 valence electrons in the Aluminium which is correctly given.
• In the case of Strontium (Sr), the atomic number is 38. The electronic configuration 2,8,18,8,2. The last shell contains 2 electrons, so there are 2 valence electrons in the Strontium which is correctly given.

Hence, the required pairs of elements and valence electrons which is incorrect is S-4.

Answer 2

Option (c) is the correct answer S - 4 pairs of elements and valence electrons is incorrect.

Explanation:

In the given options

(a) Br -7 Bromine has atomic number 35 with an electronic configuration of $2,8,8,8,7.$  the last shell is having 7 electrons

The valence electrons in bromine is 7 hence this is a correct statement.

(b) S-4 Sulphur has atomic number 16 with an electronic configuration of $2,8,6$  the last shell is having 6electrons

The valence electrons in Sulphur is 6 hence this is an incorrect statement.

In the given pairs of elements and valence electrons, S-4 is incorrect.

(c) Al-3 Aluminium has atomic number 13 with an electronic configuration of $2,8,3$  the last shell is having 6electrons

The valence electrons in Aluminium is 3 hence this is a correct statement.

(d) Sr-2 Strontium has atomic number 38 with an electronic configuration of $2,8,18,8,2$  the last shell is having 2 electrons

The valence electrons in Strontium is 2 hence this is a correct statement.

In the given pairs of elements and valence electrons, S-4 is incorrect.