Metals, Non-Metals & Metalloids | Chemistry for JEE Main & Advanced PDF Download

What are Metals?

Metals are elements that are typically good conductors of heat and electricity. They exhibit a shiny appearance when polished, which is known as metallic luster. Metals are generally malleable, meaning they can be hammered into thin sheets without breaking, and ductile, meaning they can be drawn into wires. 

Most metals are solid at room temperature, with mercury being a notable exception as it is liquid at room temperature. Metals also tend to have high densities and are often heavy. Chemically, metals tend to lose electrons during reactions, forming positively charged ions known as cations. 

Examples of metals include iron (Fe), copper (Cu), gold (Au), and aluminum (Al).

• The metals are characterised by their nature of readily giving up the electron and from shinning lusture. 
• Metals comprise more than 75% of all known elements and appear on the left-hand side of the periodic table. 
• Metals are usually solids at room temperature (except mercury). 
• They have high melting and boiling points and are good conductors of heat and electricity.
• Oxides of metals are basic in nature. (Some metals in their higher oxidation state form acid oxides e.g. CrO₃)

What are Non-Metals?

Non-metals are elements that are typically poor conductors of heat and electricity. They usually lack the shiny appearance of metals and can appear dull or glassy. Unlike metals, non-metals are brittle when solid, meaning they break easily and are neither malleable nor ductile. Non-metals can exist in various states at room temperature: they can be solid (like carbon), liquid (like bromine), or gas (like nitrogen). 

Non-metals generally have lower densities compared to metals. In chemical reactions, non-metals tend to gain or share electrons, forming negatively charged ions (anions) or covalent bonds. Examples of non-metals include carbon (C), oxygen (O), sulfur (S), and chlorine (Cl).

• Non-metals do not lose electrons but take up electrons to form corresponding anions. Non-metals are located at the top right-hand side of the periodic table. 
• Non-metals are usually solids or gases at room temperature with low melting and boiling points. They are poor conductors of heat and electricity.
• Oxides of non-metals are acidic in nature.

What are Metalloids?

Metalloids, also known as semimetals, have properties that are intermediate between those of metals and non-metals. They are semi-conductors, meaning they conduct electricity better than non-metals but not as well as metals. 

Metalloids often have a metallic luster, making them appear shiny. However, they are generally brittle like non-metals, meaning they break easily and are not malleable or ductile. All metalloids are solid at room temperature. Their densities and other physical properties fall between those of metals and non-metals. Chemically, metalloids can exhibit mixed behavior, sometimes acting like metals and other times like non-metals. Examples of metalloids include silicon (Si), boron (B), germanium (Ge), and arsenic (As). 

• It is very much clear from the periodic table that non-metallic character increases as we move from left to right across a row. It has been found that some elements lying at the border of metallic and non-metallic behaviour, possess the properties that are characteristic of both metals and non-metals.
• These elements are called semimetals or metalloids. 
• The metalloids comprise of the elements B, Si, Ge, As, Sb and Te.
• Oxides of metalloids are generally amphoteric in nature. 

Typical Elements

Elements in the third period, like Na, Mg, Al, Si, P, S, and Cl, are called typical elements. Each group of elements shares similar properties, mostly resembling the characteristics of the typical element within that group. 

• For instance, when predicting the behavior of alkali metals (Group 1), we look at Na as a model, not Li, because Na better represents the group's overall properties. 
• Elements in the second period differ noticeably within their groups due to their smaller size and the lack of available d-orbitals.

Diagonal relationship

Some elements of certain groups of 2nd period resemble much in properties with the elements of third period of next group i.e. elements of second and third period are diagonally related in properties. This phenomenon is known as diagonal relationship.

 Diagonal relationship arises because of

1. Similar size of atom and ions
   Li = 1.23 Å & Mg = 1.36 Å; Li⁺ = 0.60 Å & Mg²⁺ = 0.65 Å
2. Similar electropositive characters
3. Similar polarising powers (charge to radius ratio)
4. Similarity in electronegativity values
   (Li = 1.0 & Mg = 1.2; Be = 1.5 &AI = 1.5)

Similarities between properties of Li and Mg are as follows:

(a) Li and Mg both reacts directly with nitrogen to form lithium nitride (Li₃N) and magnesium nitride (Mg₃N₂) whereas other alkali metals of I A group does not form nitride.

(b) Fluoride, carbonate and phosphate of Li and Mg are insoluble in water whereas these compounds of other alkali metals are soluble.

(c) Li and Mg both are hard metals, whereas other metals of I A group are soft.

(d) LiOH and Mg(OH)₂ both are weak bases, whereas hydroxides of other elements of IA group are strong base.

(f) Metallic bond in Li and Mg both are strong compare to other alkali metals.

(g) Their melting and boiling points are high.

(h) By thermal disintegration of LiNO₃ and Mg (NO₃)₂ ; Li₂O and MgO is obtained respectively.

(I) Thermal stability of Li₂CO₃ and Mg CO₃ is very less compare to other alkali metals and they liberates CO₂ gas easily.

Similarly, Be shows similarity to Al of IIIA group compare to other elements of IIA group which are as follows:

(b) They both are comparatively stable in air.

(c) Both are insoluble in NH3, therefore, do not form blue coloured solution.

(d) There is no tendency of making peroxide and superoxide in them.

(e) Reducing power is very less due to low value of standard electrode potential in the form of oxidation potential.

(f) Be and AI both forms halogen bridge halides.