Mendeleev gave the name eka-aluminum to an a. compound containing aluminum. b. mixture of aluminum and an unknown element. c. unknown element he predicted would have properties similar to those of aluminum. d. rare isotope of aluminum.

C. unknown element he predicted would have properties similar to those of aluminum.

Explanation: Mendeleev arranged the elements in order of increasing atomic masses. He left spaces for the elements that were predicted to exist, but were not discovered.

One space was left below Aluminum where an element of mass 70 was predicted to exist with properties similar to Aluminum. It was referred to as eka-Aluminum.

Later it was named as gallium.

Mendeleev gave the name eka-aluminum to an C. unknown element he predicted would have properties similar to those of aluminum

The periodic system of elements is an arrangement of elements classified based on similar properties and their atomic number order.

The periodic system is divided into groups (vertical order) and periods (horizontal order)

There are some scientists who do the grouping of elements, mostly based on the relative atomic mass

These scientists grouped the elements into groups of three elements called the Triade

These scientists arrange elements based on their relative atomic mass increases called the octave law. Similarities between the elements occur in elements that  have a difference of 1 octave  (elements 1 and 8, elements 2 and 9, elements 3 and 10 etc.)

These scientists group elements based on their relative atomic mass increases.

Mendeleev placed elements that have similar properties in one group (vertical direction) and based on the increase in relative atomic mass in one period

In the periodic system made by Mendeleev, there are some parts in the group that are left blank because the element has not been found but is predicted to have the same properties as the elements in that group.

The Mendeleev periodic system is useful after the discovery of new elements which had similar properties in accordance with Mendeleev's predictions.

In group III, under the Al element, Mendeleev empties the unknown element, but it is predicted to have similar properties with aluminum and is given the name eka-aluminum. This element was later discovered and named gallium (Ga) with atomic number 31 and relative atomic mass of 69.72

electron affinity

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Identify the group number in the periodic table

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the charge on each ion in the compounds

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Keywords: element, group, period, eka-aluminum, gallium, periodic system