Question

Explain how are elements are classified ?

Answer 1

Answer:

Elements in the same group of the periodic table have similar chemical properties. Elements can beclassified as metals, metalloids, and nonmetals, or as a main-group elements, transition metals, and inner transition metals. Groups are numbered 1–18 from left to right.

Answer 2

Based on electronic configuration and properties, elements are classified in four groups.

1) Noble gases :-

✔ The $\mathsf{{18}^{th}}$ (VIII A) elements are called Noble gases.

✔ In these elements, all shells are completely filled in the electrons.

✔ These are least reactive due to octet configuration.

✔ They available in air (Ar is the most abundant)

✔ General electronic configuration is $\mathsf{{ns}^{2} {np}^{6}}$ (Except Helium, $\mathsf{{ns}^{2}}$ )

2) Representative elements :-

✔ The s and p block elements except noble gases are called representative elements.

✔ In these elements, last shell is incomplete

✔ The general electronic configuration is $\mathsf{{ns}^{1} \: to \: {ns}^{2} {ns}^{5}}$

3) Transition elements :-

✔ The d-block elements except IIB elements are called Transition elements.

✔ In these elements last two shells are incomplete.

✔ These are placed in between s and p blocks.

4) Inner transition elements :-

✔ 'f' block elements are called inner transition elements, because they are placed with in the transition elements.

✔ In these elements last three shells are incomplete.

✔ It consists of lanthanides and actinides

$\underline{\underline\mathsf{✠ \: Electronic \: configuration \: table}}$ :

$\boxed {\begin{array}{|c|c|c|c|cccc|} \sf Element & \sf Symbol & \sf Valency & \sf{Atomic\:Number} & & \sf{Electron} & \sf Configuration & \\ &&&&\bf K&\bf L &\bf M&\bf N \\ \rm Hydrogen &\sf H & 1 & 1 & 1 &&& \\ \rm Helium &\sf He & 0 & 2 & 2 &&& \\ \rm Lithium &\sf Li & 1& 3 &2 &1 && \\ \rm Beryllium &\sf Be & 2 & 4 & 2 & 2 && \\ \rm Boron &\sf B & 3 & 5 & 2 & 3 && \\ \rm Carbon & \sf C & 4 & 6 & 2 & 4 && \\ \rm Nitrogen &\sf N & 3 & 7 & 2 & 5 && \\ \rm Oxygen &\sf O & 2 & 8 & 2 & 6 && \\ \rm Fluorine &\sf F & 1 & 9 & 2 & 7 && \\ \rm Neon & \sf Ne & 0 & 10 & 2 & 8 && \\ \rm Sodium &\sf Na & 1 & 11 & 2 & 8 & 1 &\\ \rm Magnesium &\sf Mg & 2 & 12 & 2 & 8 & 2 & \\ \rm Aluminium &\sf Al & 3 & 13 & 2 & 8 & 3 & \\ \rm Silicon &\sf Si & 4 & 14 & 2 & 8 & 4 & \\ \rm Phosphorus &\sf P & 3 & 15 & 2 & 8 & 7 & \\ \rm Sulphur &\sf S & 2 & 16 & 2 & 8 & 8 & \\ \rm Chlorine &\sf Cl & 1 & 17 & 2 & 8 & 8 &1 \\ \rm Argon &\sf Ar & 0 & 18 & 2 & 8 & 8 & 2 \\ \rm Potassium &\sf K & 1 & 19 & 2 & 8 & 8 &3 \\ \rm Calcium &\sf Ca & 2 & 20 & 2 & 8 & 8 & 4 \\ \end {array}}$