Which of the following statements are NOT true about the periodic table?
A. The properties of elements are function of atomic weights.
B. The properties of elements are function of atomic numbers.
C. Elements having similar outer electronic configurations are arranged in same period.
D. An element's location reflects the quantum numbers of the last filled orbital.
E. The number of elements in a period is same as the number of atomic orbitals available in energy level that is being filled.
Choose the correct answer from the options given below:

Solution

Chemistry ma’am · 4 steps

Judge each statement on its own. E hides the catch: every orbital holds two electrons, so two elements.

1. Modern periodic law. Properties of elements are a periodic function of their atomic numbers, not their atomic weights. Mendeleev used atomic weight, and Moseley corrected the law to atomic number.
2. Groups versus periods. Elements with similar outer electronic configurations sit in the same group, one below the other. A period is a row across which the outer configuration changes from one element to the next.
3. Count the elements. Each orbital holds 2 electrons, so each orbital adds 2 elements to a period. Period 2 fills 2s and 2p, which is 4 orbitals, and it has 8 elements. Period 4 fills 4s, 3d and 4p, which is 9 orbitals, and it has 18 elements.

   Statement	Verdict	Reason
   A	Not true	Properties depend on atomic number, not atomic weight.
   B	True	This is the modern periodic law.
   C	Not true	Similar outer configurations put elements in the same group, not the same period.
   D	True	The period gives n of the outer shell and the block gives l of the last filled orbital.
   E	Not true	The number of elements is twice the number of orbitals being filled.

4. So. The statements that are not true are A, C and E, which is option (a).

The idea to keep. In a period, number of elements = 2 × number of orbitals being filled. Similar outer configuration means same group, and the modern law runs on atomic number.

Answer from the NTA final answer key. Solution by PrepWiser.