Chemistry · Periodic Classification Of Properties · NEET
Metals are on the LEFT side and the middle of the periodic table. They make up more than 78% of all known elements. Non-metals are packed in the TOP-RIGHT corner (like N, O, F, Cl, the noble gases). Between them, along a diagonal zig-zag "staircase" line, sit the metalloids. So as you read a period from left to right, elements change from metallic to non-metallic. This matters for NEET because many questions just ask you to place an element and predict its behaviour from its position.
Metallic character INCREASES down a group (top to bottom). Going down, atoms get bigger and the outer electron is held more loosely, so the atom loses electrons more easily — that is what "metallic" means. Across a period, from left to right, metallic character DECREASES because the atoms hold their electrons more tightly. Simple rule to remember: metallic character increases down and to the LEFT; non-metallic character increases up and to the RIGHT.
Use their properties. Metals are shiny solids (except mercury, a liquid), conduct heat and electricity well, and are malleable (hammered into sheets) and ductile (drawn into wires). They lose electrons to form positive ions (cations) and form BASIC oxides. Non-metals are poor conductors, often gases or brittle solids, gain electrons to form negative ions (anions), and form ACIDIC oxides. Metalloids (B, Si, Ge, As, Sb, Te) sit in between: they look metallic but behave chemically like weak non-metals and are semiconductors.
A metalloid is an element that shows properties of BOTH metals and non-metals. They lie on the zig-zag staircase line (B, Si, Ge, As, Sb, Te). For example, silicon is shiny like a metal but is a semiconductor, not a good conductor. Their oxides are often AMPHOTERIC, meaning the oxide reacts with both acids and bases. This "in-between" behaviour is exactly why they are placed on the dividing line.
Beryllium sits at the top-right edge of the metals, near the metalloid line, so it is the least metallic member of Group 2. Because metallic character increases DOWN the group (Be < Mg < Ca < Ba), the basic strength of the oxides also increases down the group. BeO is the least basic — in fact it is amphoteric (reacts with both acid and base), while MgO, CaO and BaO are clearly basic. NEET has directly asked which of BaO, BeO, MgO, CaO is most acidic — the answer is BeO.
Not exactly, but they are linked. For metals, reactivity INCREASES down a group (alkali metals get more reactive going down) because losing electrons gets easier. For non-metals, reactivity DECREASES down a group (halogens get less reactive going down) because gaining an electron gets harder. So follow metallic character for metals and non-metallic character for non-metals — do not use one single "reactivity" rule for the whole table.
The correct order of increasing metallic character of Na, Be, P, Mg and Si is:
The correct sequence given below, containing a neutral, an acidic, a basic and an amphoteric oxide respectively, is:
Which one of the following oxides is most acidic in nature?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Hydrogen is placed at the top of the table but behaves like a non-metal under normal conditions. It is a special case and does not fit neatly into one group, which is why it is often shown on its own.
Yes. "Semi-metal" is another common name for a metalloid. The standard NEET metalloids are boron, silicon, germanium, arsenic, antimony and tellurium (B, Si, Ge, As, Sb, Te).
Among stable elements, caesium (Cs) is the most metallic because it sits at the bottom-left of the table and loses its outer electron most easily. Francium is below it but is radioactive and rare.
Metals lose electrons easily and their oxides react with acids (basic oxides). Non-metals form oxides that react with water to give acids (acidic oxides). Metalloids and borderline metals often form amphoteric oxides that react with both.
NEET regularly asks you to order elements by metallic character or to classify oxides as acidic, basic, neutral or amphoteric. Both depend on where the element sits in the table, so mastering this one idea answers several questions each year.
