Question

Elements having atomic no 4 9 14 19 20 of a b c d e resp (a) which two elements belong to same period (b) which two element's belong to same group

Answer 1

Answer:

a) a & b are in same period

Explanation:

b) a & e are  in same group

Answer 2

To find out the group number and period of the elements, we will find out the electronic configuration first.

The electronic configuration of an element with atomic no. 4 is:

• 2,2
• So the number of electrons in the outermost shell gives the group number so the group of the element with atomic number 4 is 2, the alkaline earth metals.
• And the number of shells in an element gives us the period to which the element belongs, then the period of the element with atomic number 4 is 2.

The electronic configuration of an element with atomic no. 9 is:

• 2,7
• So the number of electrons in the outermost shell gives the group number so the group of the element with atomic number 9 is 7 which is the 17th group, the halogen family.
• And the number of shells in an element gives us the period to which the element belongs, then the period of the element with atomic number 9 is 2.

The electronic configuration of an element with atomic no. 14 is:

• 2,8,4
• So the number of electrons in the outermost shell gives the group number so the group of the element with atomic number 14 is 4, which is the 14th group, the carbon family.
• And the number of shells in an element gives us the period to which the element belongs, then the period of the element with atomic number 14 is 3.

The electronic configuration of an element with atomic no. 19 is:

• 2,8,8,1
• So the number of electrons in the outermost shell gives the group number so the group of the element with atomic number 19 is 1, the alkali metals.
• And the number of shells in an element gives us the period to which the element belongs, then the period of the element with atomic number 19 is 4.

The electronic configuration of an element with atomic no. 20 is:

• 2,8,8,2
• So the number of electrons in the outermost shell gives the group number so the group of the element with atomic number 20 is 2, the alkaline earth metals.
• And the number of shells in an element gives us the period to which the element belongs, then the period of the element with atomic number 20 is 2.

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