Question

Which of the given elements A, B, C, D and E with atomic number 2,3,7,10 and 30 respectively belong to the same period?
A.A, B, C
B.B, C, D
C.A, D, E
D.B, D, E

Answer 1

Hint:We are aware that all the elements in a row have the same number of electron shells. A period in the periodic table is a row of chemical elements. Each next element in a period has one more proton and is less metallic than its predecessor.

Complete answer:
We know that elements are grouped into a period depending on the valence shell that is being filled.
The first period contains the least elements than any other, with only two elements, hydrogen and helium. Therefore, the first period contains 1−2 atomic numbers.
The second period contains 3−10 atomic numbers. It contains 8 elements and the elements involve the 2s and 2p orbitals. They include the biologically most essential elements besides hydrogen: carbon, nitrogen, and oxygen.
The third period contains 8 elements. The third contains 11 to 18 atomic numbers.
The fourth period contains 19 to 36 atomic numbers. Period 4 includes the biologically essential elements potassium and calcium, and is the first period in the d-block with the lighter transition metals. These include iron, the heaviest element forged in main-sequence stars and a principal component of the Earth, as well as other important metals such as cobalt, nickel, and copper. Almost all have biological roles.
So, for A, the first shell is being filled so it belongs to the first period.
For B, C, D, the second shell is being filled, so they belong to the second period.
For E, the fourth shell is being filled, so it belongs to the fourth period.
So B, C, D belong to the same period.

Therefore, the correct answer is option (B).
Note:
In a periodic table, the elements are arranged in a series of rows. Elements of the same period have the same number of electron shells. A period in the periodic table is a row of chemical elements. There are currently seven complete periods in the periodic table, comprising the 118 known elements.