Periodic Table

The correct name is Dmitri Ivanovich Mendeleev (D.I. Mendelief), who is credited with creating the Periodic Table of Elements. Mendeleev's periodic table was organized based on atomic mass, and it highlighted the periodicity of elements' properties.

In the modern periodic table, elements are arranged according to their increasing atomic number (the number of protons in the nucleus). This arrangement helps in classifying elements based on their electronic configuration, and it also leads to the periodicity of their chemical and physical properties.

The first ionisation energy is the energy required to remove the outermost electron from a neutral atom. For group 13 elements (B, Al, Ga, In), ionisation energy generally decreases down the group due to increasing atomic size, but anomalies occur due to electron configurations.
Step 1: Electron configurations
- B (atomic number 5):
- Al (13):
- Ga (31):
- In (49):
Step 2: Group 13 trends
- Atomic size: Increases down the group (B , so the electron is removed from the orbital.
- Anomaly: Ga’s filled subshell provides poor shielding, increasing effective nuclear charge, so Ga has higher ionisation energy than Al.
Step 3: Ionisation energies
- B: ~801 kJ/mol (smallest, highest ionisation energy). - Al: ~577 kJ/mol. - Ga: ~579 kJ/mol (slightly higher than Al due to ). - In: ~558 kJ/mol (largest, lowest ionisation energy).
Step 4: Order
Highest to lowest: This matches option (B).

Step 1: Verify each option
\begin{tabular}{lll} Option & Element & Correct Atomic Number
(a) Sg & Seaborgium & 106 (Correct)
(b) Mt & Meitnerium & 109 (Correct)
(c) Bh & Bohrium & 107 (Not 105)
(d) Hs & Hassium & 108 (Correct)
\end{tabular}
Step 2: Identify the mismatch
Bohrium (Bh) has atomic number 107, not 105 as given in option (c). The element with atomic number 105 is Dubnium (Db).
Step 3: Confirm other options
All other options correctly match:
- Sg (Seaborgium) is indeed element 106
- Mt (Meitnerium) is element 109
- Hs (Hassium) is element 108
Step 4: Conclusion
Only option (c) presents an incorrect match between the element symbol and atomic number.