Question

The wrong statement among the following is (1) Mcndclcev arranged the Elements in a tabular form according to increasing atomic weight. (2) Onc of the dcfects in Mcndclcev's periodic table is position of lanthanides. (3) Maximum number of groups in Bohr's periodic table is 18 . (4) Elements with similar chemical properties occur only within the same period.

Short answer

The incorrect statement is option (4).

Step-by-step solution

Analyze Each Statement

Carefully read each of the options provided and determine if the statement is valid based on known periodic table principles.

Verify Mendeleev's Arrangement

Mendeleev arranged the elements according to increasing atomic weight as stated in option (1). This is historically accurate, so it is a correct statement.

Identify the Defect in Mendeleev's Table

Mendeleev's periodic table indeed had issues with the positioning of the lanthanides, which aligns with option (2). Hence, it is a correct statement.

Confirm Bohr's Group Numbers

Bohr's periodic table does have 18 groups, as stated in option (3). This is correct based on modern understanding of the periodic table.

Evaluate Chemical Properties Relationship

Elements with similar chemical properties are found within the same group, not the same period as stated in option (4). Therefore, this statement is incorrect.

Key concepts

atomic weight arrangement

Mendeleev, a pioneer in the organization of elements, created the first widely recognized periodic table. He arranged elements in increasing order of their atomic weights.
Unlike modern tables which use atomic numbers, Mendeleev prioritized atomic mass to predict new elements and correct assumed atomic weights.
For example, he placed tellurium before iodine despite its higher atomic weight to maintain chemical behavior consistency.
This ordering paved the way for discovering the periodic law, emphasizing periodicity in element properties.

defects in Mendeleev's table

While Mendeleev's periodic table was groundbreaking, it had several notable defects. One major flaw was the positioning of the lanthanides.
These elements did not fit neatly into Mendeleev's arrangement and were awkwardly placed.
Additionally, using atomic weight sometimes led to misplaced elements as anomalies.
For instance, argon and potassium posed a challenge due to their reversed positions in terms of atomic weight.
Mendeleev's model, though revolutionary, required adjustments that later periodic tables, like Bohr’s, addressed more effectively.

groups in Bohr's periodic table

Bohr's periodic table introduced significant improvements, including the concept of electron shells. He maintained 18 groups, aligning with our contemporary understanding.
These groups signify elements with shared valence electron configurations and similar chemical behaviors.
Bohr’s model helped explain periodic trends better by associating element properties with electronic structure.
This clarity was a major advancement, leading to more precise predictions about element behavior.
Each group in Bohr’s table played a crucial role in recognizing patterns among elements, thus enhancing the periodic table's utility.

chemical properties in periods

Elements within the same period, or horizontal row, show gradual but noticeable changes in chemical properties.
Moving across a period, elements shift from metals to metalloids to non-metals.
This transition reflects increasing electronegativity and ionization energy attributes.
However, similar chemical properties most accurately occur within groups, or vertical columns, where elements share valence electron characteristics.
For instance, all noble gases in Group 18 have complete outer shells, making them inert.
Understanding these trends is key to grasping the logic behind element behaviors.