Groups of three elements each, having similar chemical properties, arranged in increasing order of atomic mass where the atomic mass of the middle element is approximately equal to the mean of theatomic masses of the other two elements
Dobereiner's Triads
Li, Na, K
Ca, Sr, Ba
Cl, Br, I
Dobereiner's Triads could not classify all the known elements at the time
Potential Dobereiner's Triads
Mg, Ca, Sr
S, Se, Te
Be, Mg, Ca
Around year 1800 only about 30 elements were known, but more elements were discovered over time
Elements were initially classified into groups of metals, nonmetals, and metalloids as knowledge about elements and their properties increased
Scientists tried different methods of classifying the increasing number of known elements
Endocrinology is the branch of medicine dealing with the endocrine system.
