## How has the periodic table changed since Mendeleev?

The periodic table has long-since filled in Mendeleev’s gaps and has added new elements. It has even changed the weights of other elements. The periodic table is continually being changed as new discoveries are made and new theories are developed to explain the behavior of chemicals.

## How did Mendeleev organize the first periodic table?

In 1869, Mendeleev published the first periodic table of the elements. In his periodic table, Mendeleev arranged elements in rows by increasing atomic mass. Within a row, elements with lower atomic masses were on the left. Thus, all the elements in a column had similar properties.

## What is dobereiner triads give examples?

He arranged the three elements in a triad in an increasing order of atomic mass and showed that the atomic mass of the middle element was approximately equal to the mean of the atomic masses of the other elements. Examples : Lithium (Li), Sodium (Na), Potassium (K) from Dobereiner’s tried.

## Is P as SB a dobereiner Triad?

Using his triad rule, we can determine the atomic weight of arsenic (As) when the atomic weight of phosphorus(P) and antimony (Sb) is given, 31 and 120 respectively. Their average will result in the atomic weight of arsenic as per Dobereiner’s triad rule. Hence, the correct option is (B).

## Is Cu Ag Au a triad?

Answer: cu ag au is the answer as dobereniers law does not hold true for these elements. Explanation: try finding the avg at mass of cu and au.. it is not equal to mass of ag.

## Which pair will not follow Newland rule of octave?

Cl and Br did not follow the trend of Newland’s octave as they are coming after Calcium. So, the correct answer is option D. (ii) Not all the elements discovered fit into the same slots in Newland’s periodic classification. For example, cobalt and nickel were placed in the same slot.

## What was a shortcoming of the Triad system?

What was a shortcoming of the triad system? a limitation of the triad system was that not all of the known elements could be classified in this way.