Question

4. Why did Mendeleev concentrate

on the compounds formed by

elements with oxygen and

hydrogen?

5. Complete the sentence:

In Mendeleev’s Periodic Table

vertical columns are called

……………..and horizontal rows as

…………..​

Answer 1

$\rm{\purple{\huge{Question:}}}$

Why did Mendeleev concentrate on the compounds formed by elements with oxygen and hydrogen ?

$\rm{\purple{\huge{Answer:}}}$

➡️Among the chemical properties, he concentrated on the compounds formed by elements with hydrogen and oxygen,

➡️He selected hydrogen and oxygen as they are very reactive and formed compounds with most elements.

➡️He sorted out the elements with similar properties and paired the cards together on a wall.

Answer 2

Explanation:

5.

groups - vertical columns

periods - horizontal rows