Question

3. a. Why do we classify elements?
b. Why did Mendeleev leave some gaps in his periodic table?
c. What were the two criteria used be Mendeleev to classify the elements in creating
his table?​

Answer 1

Answer:

(b) Mendeleev used atomic mass and similarities in chemical properties to classify the elements. ... That's why Mendeleev didn't placed Nobel gases in the periodic table. When they were discovered, they were placed in a different group so that they don't create any difference in the periodic table.

Explanation:

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Answer 2

Answer:

a) It enables chemists to predict the properties of the elements and their compounds based on their positions in the Periodic Table, and vice versa. It becomes easier to study, understand, compare and contrast the related properties among the elements and their compounds from different groups

b) Mendeleev left spaces in his periodic table because he predicted there were elements that weren't discovered yet that would fit in these spaces.

c) 1- Increasing atomic masses of the elements. 2- Elements with similar chemical properties were placed in a group. He suggested that the properties of the elements are periodic functions of their atomic masses. This was known as periodic law.