Mendeleev's Periodic Table

Question 1

Define Mendeleev’s Periodic Law.

Answer 1

When elements are arranged in order of increasing atomic weight (relative atomic mass), the properties of the elements recur periodically, i.e. the properties displayed by an element are repeated at regular intervals in other elements

Question 2

What did Dmitri Mendeleev do?

Answer 2

He arranged the elements in order of increasing atomic weight (relative atomic mass) and placed elements with similar properties under each other in groups.

Question 3

Summarise Mendeleev’s work (4)

Answer 3

1. He placed all elements with similar properties in the same vertical column. This was called the periodic table of the elements.
2. Mendeleev left gaps in his table. The gaps represented elements that had yet to be discovered.
3. Mendeleev predicted the properties of undiscovered elements. It was found that the properties predicted by Mendeleev were almost identical to the observed properties.
4. Mendeleev reversed the order of some elements (in order to make them fall into groups of elements with similar properties). Tellurium and iodine switched places regardless of atomic weight.
   He realised that the properties were more important than the atomic weights and so he reversed the order of atomic weights so that each element would be in a group with elements of similar properties.

Question 4

Why did Mendeleev reverse the order of some elements?

Answer 4

He realised that the properties were more important than the atomic weights and so he reversed the order of atomic weights so that each element would be in a group with elements of similar properties.