MediumChemistryHigh School (11–12)The Periodic Table › Development of the Periodic TableNumericalpythonBoard Exam

In Mendeleev's table the gap for eka-silicon had silicon (28.09 u) above, tin (118.71 u) below…

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

In Mendeleev's table the gap for eka-silicon had silicon ( $28.09$ u) above, tin ( $118.71$ u) below, gallium ( $69.72$ u) to the left and arsenic ( $74.92$ u) to the right. Predict its atomic mass as the mean of the four neighbours. Germanium, found in 1886, has $72.63$ u. By what percentage is the prediction off?

Need a reminder? The key ideaShow

Dobereiner's triads: the atomic mass of the middle element of three similar elements is close to the mean of the other two. Newlands' law of octaves: every eighth element, in order of atomic mass, is like the first. Mendeleev's periodic law: the properties of the elements are a periodic function of their atomic masses; he left gaps and predicted unknown elements from their neighbours.

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

← All Problems

← Calcium (40.08 u), strontium (87.62 u) and barium (137.33 u) behave alike…Newlands' list, in order of atomic mass, began: H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl… →

More onThe Periodic Table › Development of the Periodic Table

Discussion (0)

Loading…