### Core Logic Fluorine is the most electronegative element and lacks vacant d-orbitals in its valence shell. Consequently, it exhibits only a -1$-1$ oxidation state (and 0$0$ in elemental form) and cannot show variable positive oxidation states unlike other halogens. ### Pattern Recognition First element of a group lacks d-orbitals rightarrow$\rightarrow$ anomalous properties rightarrow$\rightarrow$ Fluorine only exhibits -1$-1$. ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties

### Core Logic Statement I is true: The lanthanides (4textf$4\text{f}$) and actinides (5textf$5\text{f}$) are separated at the bottom of the periodic table to avoid distortion of the periodic trends layout and preserve clean structural classification groups. Statement II is false: s-block elements (alkali and alkaline earth metals) possess exceptionally low ionization energies, making them highly reactive; thus, they are always encountered as compounds rather than in native pure forms in nature. ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties

### Core Logic Statement I: Along a period, the chemical reactivity of elements first decreases and then increases. Group 1 elements (alkali metals) are highly reactive, Group 17 elements (halogens) are also highly reactive, but the elements in the middle (like carbon) are less reactive. Moreover, Group 18 elements (noble gases) are mostly inert. Therefore, statement I is false. Statement II: Group 1 elements are metals and form basic oxides (e.g., Na_2O$Na_2O$). Group 17 elements are non-metals and form acidic oxides (e.g., Cl_2O_7$Cl_2O_7$). Therefore, statement II is true. ### Pattern Recognition Reactivity is highest at the extreme left (Group 1) and extreme right (Group 17) of the periodic table, excluding noble gases. Metallic character = basic oxides; Non-metallic character = acidic oxides. ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties

### Core Logic Decode the IUPAC name "Unununnium" into its atomic number. Un = 1 Un = 1 Un = 1 Suffix = ium So, the atomic number is 111. ### Step 1: Finding group number For d-block elements with Z > 100, the group number is the last two digits of the atomic number. Since Z = 111, the element belongs to group 11 (the Copper group). ### Evaluation Rubric / Model Answer null ### Chapter Mix Class 11 Chemistry: Classification of Elements and Periodicity in Properties