Science : Ch 05 – Periodic of Classification of Elements

Atomic number X- 12 ,Y-17 Number of protons X-12, Y-17 Number of electrons X-12,Y- 17 Electronic configuration 2, 8, 2 2, 8, 7 Valence electrons X-2,Y- 7 Valency X- 2,Y- 1

The element with electronic confguration 2, 8 has octet confguration, so it must be an inert gas, i.e., neon, which is placed in group 18.

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.

Element  Y  has 1 less electron to complete its octet which is a property of nonmetals. On the other hand, element  Z  has 2 extra electrons to become stable which is a property of metals.

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.

As we move down in a group, the metallic nature of elements increases.  Be, Mg and Ca are present in the same group (group 2 of the modern periodic table).