part c

Look at the two question marks between zinc (Zn) and arsenic (As). At the time, no elements were known with atomic weights between 65.2 and 75. But Mendeleev predicted that two elements must exist with atomic weights in this range. What led Mendeleev to predict that two undiscovered elements existed in that range?

part d
The two elements predicted by Mendeleev were discovered later. Locate the elements gallium (Ga) and germanium (Ge) in the periodic table. Click each element to reveal its properties. Explain how these elements fit Mendeleev’s predictions.

Both recognized that the elements have repeating properties but Mendeleev realized that there are elements yet to be discovered while Newlands tried to fit the known elements together.

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Adetunmbiadekunle Adetunmbiadekunle · Answer 2 · 2021-09-16T15:51:11+02:00

Part C

Mendeleev arranged elements in the periodic table in increasing order of atomic numbers, such that elements having similar chemical properties fall into the same group.

Mendeleev discovered that two elements existed between atomic weights 65.2 and 75 because he knew quite well the properties of the elements closer to this range and he expected to have other elements that would have their properties similar to these other elements. Therefore, he left a gap for these two elements in the periodic table until they were eventually discovered.

Part D

Gallium

1) has low melting point

2) is a good conductor of heat

3) has a density of 5.9 g/cm^3

4) Has a shining lustre

All these properties are in consonance with Mendeleev's predictions

Germanium:

1) has a melting point of 938 degree Celsius

2) has an atomic weight of 72.64u

3) is hard

4) greyish-white in color

These are approximate to Mendeleev's prediction

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