Lothar Meyer’s Contribution to Periodic Table (JEE/NEET Concepts)

Julius Lothar Meyer (1869) was a German chemist who independently worked on classification of elements, around the same time as Dmitri Mendeleev.

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Key Idea of Lothar Meyer

He arranged elements based on:

• Atomic mass
• Valency (combining capacity)
• Physical properties

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Most Important Contribution

Atomic Volume vs Atomic Mass Graph

He plotted a graph between:

• Atomic Volume (volume occupied by 1 mole of element)
• Atomic Mass

This graph showed a periodic pattern, proving that properties repeat regularly.

On the atomic volume vs atomic mass curve given by
Julius Lothar Meyer, elements occupy characteristic positions depending on their properties.

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1. Peaks (Maxima) → Highly Reactive Metals

Elements at the top of the curve

• Alkali metals:
  • Li, Na, K, Rb, Cs

✔ Features:

• Maximum atomic volume
• Highly reactive
• Valency = +1

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2. Just After Peaks → Alkaline Earth Metals

Slightly lower than peaks

• Be, Mg, Ca, Sr, Ba

✔ Features:

• Less reactive than alkali metals
• Valency = +2

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3. Descending Region → Transition Elements

Moving downward from peak

• Fe, Co, Ni, etc.

✔ Features:

• Moderate atomic volume
• Variable valency
• Metallic character

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4. Troughs (Minima) → Least Reactive Elements

Bottom of the curve

• Elements like:
  • Cu, Zn (near minima region)

✔ Features:

• Minimum atomic volume
• Stable nature

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5. Rising Region → Non-metals

Moving upward after minima

• C, N, O, F

✔ Features:

• Increasing electronegativity
• Non-metallic character increases