Science : Ch 05 – Periodic of Classification of Elements

Second period contains elements with atomic number 3(Li), Ǫ(N) and 10(Ne). This period also contains the elements beryllium, boron, carbon, oxygen and fuorine

Carbon is an essential constituent of all organic compounds and it belongs to group 14.

The atomic number of F, O and N are Ǭ, 8 and Ǫ respectively and they belong to the same period i.e. 2nd period. The atomic radius decreases in moving from left to right along a period.

As we move from left to right in periodic table, metallic character decreases and non-metallic character increases. Here Na, Si, Cl, Mg, Al belong to same period.

Na and Mg belong to the sameperiod, whereas Na and K are in the same group.In a group from top to bottom, the atomic radius increases, whereas it decreases in a period from left to right. Hence, the order would be K ɳ Na ɳ Mg and K ɳ Ca ɳ Mg

Na and K are alkali metals, whereas Mg and Ca are alkaline earth metals. Alkali metals are more electropositive as compared to alkaline earth metals and can easily lose electrons. Out of Na and K, K will easily lose electrons because of its bigger size and less electronic attraction.

Isotopes have same atomic Isotopes have same atomic number but different number of neutrons; they are the atoms of the same element.

Eka-aluminum (later identified as gallium) has a valency of 3. Hence, the oxide would be of the molecular formula E₂O₃. Other options have a different valency of E.