Observe the following trends in the periodic properties, in the periodic table. Identify the properties X, Y, P and Q respectively.

Effective nuclear charge, Non-metallic character, Atomic size, Metallic character

Metallic character, Electronegativity, Effective nuclear charge, Valency

Atomic size, Metallic character, Valency, Non-metallic character

Valency, Non-metallic character, Electronegativity, Effective nuclear charge

Use Mendeleev's Periodic table to predict the formulae for the oxides of the following elements: K , C , Al , Si

According to Mendeleev's periodic table, the elements K , C , Al , Si are present in group I , IVA , III and IVA respectively. Hence, their oxides will be K 2 O , CO 2 , Al 2 O 3 and SiO 2 .

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

The criteria used by Mendeleev in creating his Periodic Table are: (i) Elements were arranged in the increasing order of their atomic masses. (ii) All elements in a group should have similar chemical properties. That is, he used the criteria that the element with similar chemical properties should be in the same group.