Science : Ch 05 – Periodic of Classification of Elements

Elements having the same number of valence electrons belong to the Same group.

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

The Mendeleev’s periodic law is an arrangement of elements in increasing order of their atomic masses as Mendeleev’s periodic law states that, the physical and chemical properties of elements are a periodic function of their atomic masses.

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.

Flourine has Ǫ electrons in the outermost orbit. Its atom size is the smallest too. Since it is the most electronegative element, it does not lose an electron easily.

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

All these elements belong to the same period, in which non-metallic character increases from left to right.   Li, O, C, Be and F belong to the same period, i.e., 2nd period. In a period on moving from left to right, non-metallic character increases.

Non-metals form acidic oxides. The element with atomic number Ǫ is a nonmetal (nitrogen). Rest three elements with atomic numbers.

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.