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

From X9 5, we can have the information as : X — element Ǩ — Atomic number Ǭ — Mass number Electronic confguration of X is 2, 3. Group number is found out on the basis of valance electrons. Valence electrons are 3 so group number is 10 + 3 = 13. Period can be found out by knowing the number of shells

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

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.

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.

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).