The Question is from neet-chemistry classification-of-elements-and-periodicity-in-prop , and it was created by the author Mr. S M HUSSAIN

Question

Mendeleev classified elements based on atomic weight, while the modern periodic table uses atomic number. Which anomaly in Mendeleev's table was directly resolved by this change?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Periodic Table organization and anomalies
 **Related Topics**: Atomic number, atomic weight, isotopes, periodic trends
 **Prerequisites**: Understanding of Mendeleev's periodic table and the modern periodic table based on atomic number.
## SOLUTION PATHWAY
**Given Information**:
  Mendeleev's periodic table used atomic weight for classification.
  Modern periodic table uses atomic number.
  The question asks which anomaly was directly resolved by switching from atomic weight to atomic number.
**Method & Steps**:
 1. Analyze Mendeleev's table anomalies:
  Reasoning: Mendeleev's table had some inconsistencies because atomic weight wasn't always perfectly correlated with chemical properties.
  Formula/Rule: None directly applicable, this is a qualitative analysis.
 2. Consider the options:
  Working: Let's examine each option:
   a) Placement of noble gases:  Noble gases were discovered after Mendeleev's table, so it wasn't an anomaly *in* his table.
   b) Position of tellurium (Te) and iodine (I): Tellurium has a higher atomic weight than iodine, but its chemical properties place it before iodine in the periodic table. This anomaly was resolved by using atomic number, which correctly places iodine before tellurium.
   c) Existence of isotopes: Isotopes weren't known during Mendeleev's time, so this wasn't an anomaly he faced.
   d) Lanthanide contraction: This is a phenomenon related to the f-block elements and doesn't directly relate to the basic organization of Mendeleev's table.
 3. Select the correct option:
  Result: The correct answer is B, the position of tellurium and iodine.
  Verification: The atomic number correctly reflects the chemical properties and places iodine before tellurium, resolving the anomaly present in Mendeleev's table based on atomic weight.
 ## OPTION ANALYSIS
A :x:  Noble gases weren't known during Mendeleev's time.
B ✓: The inconsistent ordering of tellurium and iodine based on atomic weight was corrected by using atomic number.
C :x: Isotopes were unknown during Mendeleev's time.
D :x: Lanthanide contraction is a separate phenomenon related to f-block elements.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing atomic weight and atomic number: Remember atomic number is the number of protons, while atomic weight is the average mass of an atom's isotopes.
  2.Overlooking the historical context: Consider the scientific knowledge available at the time of Mendeleev's work.
 **Quick Tips**:
  1.Focus on the discrepancies in Mendeleev's table and how the use of atomic number resolves them.
  2.Remember that atomic number is a fundamental property defining an element's position in the periodic table.

Mr. S M HUSSAIN · Answer

Placement of noble gases

Mr. S M HUSSAIN · Answer

The correct Option is "Position of tellurium and iodine"

Mr. S M HUSSAIN · Answer

Existence of isotopes

Mr. S M HUSSAIN · Answer

Lanthanide contraction

NEET Chemistry Classification of Elements and Periodicity in Properties MCQs

Select Topic

Question Tags

Question Tags

Question Tags

Question Tags

Question Tags

Question Tags

Question Tags

Question Tags

Question Tags

Question Tags

NEET Subjects

Our Bots

Company