EXERCISE

According to modern periodic law, the properties of elements are a periodic function of their

Which of the following is the most non-metallic element?

Which of the following statements does not apply to elements belonging to the same period of the periodic table?

Why do we classify elements?

What were the two criteria used by Mendeleev in creating his periodic table? 

In Mendeleev's periodic table, why was there no mention of noble gases like helium, neon, and argon?

Would you place the two isotopes of chlorine, $\mathrm{Cl}-35$ and $\mathrm{Cl}-37$ in different slots because of their different atomic masses or in the same slot because their chemical properties are the same? Justify your answer.

What is the number of electrons in ${\mathrm{Cl}}^{-}$ Ion? ($\mathrm{Cl} =17$)