The Question is from neet-chemistry , and it was created by the author Mr. S M HUSSAIN

Question

Mendeleev left gaps in his periodic table for undiscovered elements. Which of the following properties was NOT used by him to predict the properties of these missing elements?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: D
## CONCEPT FRAMEWORK
 **Primary Concept**: Mendeleev's Periodic Table and its predictive power
 **Related Topics**: Periodic trends, atomic properties, chemical properties
 **Prerequisites**: Basic understanding of the periodic table and its organization based on atomic weight and recurring chemical properties.
## SOLUTION PATHWAY
**Given Information**:
Mendeleev's periodic table had gaps for undiscovered elements. He predicted the properties of these elements.
**Method & Steps**:
1. Identify properties used by Mendeleev:
Mendeleev arranged elements in order of increasing atomic weight and observed recurring patterns in their properties. He used the properties of elements surrounding a gap to predict the properties of the missing element.  These properties included atomic weight, density, and the formulae of their oxides and hydrides. These properties showed trends across periods and groups.
2. Identify the property NOT used:
Radioactive decay properties were unknown during Mendeleev's time (late 19th century).  Radioactivity was discovered much later (1896 by Becquerel).
3. Conclusion:
Therefore, Mendeleev could not have used radioactive decay properties to predict the properties of undiscovered elements.
  Result: D
  Verification: The other options (atomic weight, density, and formulae of oxides and hydrides) are all properties that exhibit periodic trends and were known and utilized by Mendeleev.
 ## OPTION ANALYSIS
A ✓: Atomic weight was the primary organizing principle of Mendeleev's table.
B ✓: Density is a physical property showing periodic trends.
C ✓: Formulae of oxides and hydrides reflect chemical properties and their periodic variation.
D :x: Radioactive decay properties were unknown at the time of Mendeleev's work and therefore could not have been used in his predictions. 
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing Mendeleev's table with the modern periodic table (organized by atomic number).: Remember that Mendeleev's table was based on atomic weight, which was the best available information at the time.
  2. Assuming all properties were used equally.: Mendeleev relied more heavily on some properties than others when making predictions. 
 **Quick Tips**:
  1.Focus on the historical context of Mendeleev's work.: Understanding the scientific knowledge of his time is crucial to answering this question.
  2.Remember the key properties used for prediction: atomic weight, density, and chemical formulas (oxides and hydrides) are the key to this question.

Mr. S M HUSSAIN · Answer

Atomic weight

Mr. S M HUSSAIN · Answer

Density

Mr. S M HUSSAIN · Answer

Formulae of oxides and hydrides

Mr. S M HUSSAIN · Answer

The correct Option is "Radioactive decay properties"

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