Question

Dobereiner laid down the ______ rule.

Options

• periodic

• modern periodic

• triad

• octaves

Answer 1

Dobereiner laid down the triad rule.

Explanation

Johann Wolfgang Döbereiner proposed the Law of Triads in 1817. According to this rule, when elements with similar properties are arranged in a group of three (called a triad) in increasing order of their atomic masses, the atomic mass of the middle element is approximately the arithmetic mean of the atomic masses of the other two elements.