As the number of known elements grew, so did the need to organize them into groups based on their properties.

The first elements to be identified were mainly gases including the Noble gases.

Mendeleev knew the name, relative mass and the properties of the 63 ____ known at the time.

Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar ____ were in the same column.

Mendeleev left some locations in his periodic table blank for ____ elements.

Mendeleev used the properties of elements located near the spaces in his table to predict ____ for undiscovered elements.

The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be.

Mendeleev was the first, and only, scientist to arrange elements in a periodic table.

Mendeleev arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same ____.