Question

1. There are two triads mentioned in the paragraph

Suggest a physical property of:

a) the metals in one triad

b) the non-metals in the other triad.

[That paragraph is in the pic]​

Answer 1

Such triads—including chlorine-bromine-iodine, calcium-strontium-barium, and sulfur-selenium-tellurium—were noted by the German chemist J.W. Döbereiner between 1817 and 1829. The triad was the earliest atomic-weight classification of the elements.