Atomic weight and noble gases in Mendelev's periodic table

Thread starter mahrap
Start date Oct 6, 2012
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Atomic Gases Noble gases Periodic Periodic table Table Weight

In summary, atomic weight is the average mass of all the naturally occurring isotopes of an element, expressed in atomic mass units. It is determined by the relative abundance and mass of each isotope and is an important characteristic for understanding an element's chemical properties. Noble gases, a group of elements with a full outer electron shell and unique chemical properties, are placed separately in Mendeleev's periodic table due to their similarities and differences from other elements. The atomic weight also plays a crucial role in an element's placement in the periodic table, as elements with similar atomic weights tend to have similar chemical properties and the atomic weight generally increases across a period in the table.

Oct 6, 2012

mahrap

Why did Mendelev order the elements according to their atomic masses rather than their atomic number?

Why did Mendelev not include noble gases in his periodic table?

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Oct 6, 2012

AGNuke

Gold Member

Simple : Because Noble gases weren't discovered at the time Mendeleev introduced his Periodic table.

1. What is atomic weight?

Atomic weight is the average mass of all the naturally occurring isotopes of an element. It is expressed in atomic mass units (amu) and is an important characteristic of an element for understanding its chemical properties.

2. How is atomic weight determined?

Atomic weight is determined by taking into account the relative abundance and mass of each isotope of an element. The more abundant an isotope is, the more it contributes to the overall atomic weight of the element.

3. What are noble gases?

Noble gases are a group of elements in the periodic table that have a full outer electron shell, making them very stable and unreactive. This group includes helium, neon, argon, krypton, xenon, and radon.

4. Why are noble gases placed in a separate group in Mendelev's periodic table?

Noble gases are placed in a separate group in Mendelev's periodic table because they have unique chemical properties and do not easily fit into any other group. They also have similar atomic structures and share common characteristics, making it logical to group them together.

5. How does atomic weight affect an element's placement in the periodic table?

The atomic weight of an element plays a crucial role in its placement in the periodic table. Elements with similar atomic weights are usually placed in the same group, as they share similar chemical properties. Additionally, as you move across a period in the periodic table, the atomic weight generally increases, reflecting the trend of increasing atomic mass in elements.