Metals Are on the Left, Non-Metals on the Right

What students typically write

“Metals are on the right side of the periodic table and non-metals are on the left.” Or students draw the dividing line in the wrong place, putting common metals like iron and copper on the non-metal side.

This is a straightforward left-right reversal. Students know there is a divide but get the sides backwards, or they have not studied the table carefully enough to know where the boundary falls.

Why it is wrong

The periodic table has metals on the left and in the centre, and non-metals on the upper right. About 80 of the 118 elements are metals. The non-metals are confined to the upper-right corner.

The dividing line is not a simple vertical cut. It runs as a diagonal staircase starting from boron (B, element 5) and stepping down through silicon, arsenic, tellurium, and astatine. Elements to the left and below this line are metals. Elements to the right and above it are non-metals.

Elements along or near the staircase line (boron, silicon, germanium, arsenic, antimony, tellurium) are sometimes called metalloids or semi-metals. They have intermediate properties. Silicon, for example, is a semiconductor, which is why it is used in computer chips. It conducts electricity, but not as well as a metal.

Note that hydrogen sits in Group I on the left side but is a non-metal. Its placement reflects its electron configuration (one outer electron), not its metallic character.

What the mark scheme actually wants

A typical question: “On the outline of the periodic table, draw a line to separate metals from non-metals.” [1]

The marking point requires the line to run roughly diagonally from top-right to bottom-left, separating the small non-metal region (upper right) from the large metal region (left and centre).

A question asking “State whether silicon is a metal or a non-metal and explain your answer” typically expects: “Silicon is a metalloid / has properties of both metals and non-metals” for 1-2 marks.

Worked example: wrong vs right

Question: An element has the following properties: it is a solid at room temperature, conducts electricity, and is shiny. Is it most likely a metal or a non-metal? In which part of the periodic table would you find it? [2]

Wrong answer: “It is a metal because metals are shiny and conduct. It would be on the right side of the periodic table.” This scores 1/2. The identification is correct but the position is wrong.

Right answer: “It is most likely a metal because it is a solid conductor with a shiny appearance (1). It would be found on the left or in the centre of the periodic table (1).” This scores 2/2.

How to avoid this mistake

Remember: there are far more metals than non-metals. Metals dominate the periodic table. The non-metals are a relatively small cluster in the upper-right corner. If you remember that non-metals are the minority squeezed into the corner, you will not put them on the wrong side.

For exam purposes, know the exact position of the staircase line and be able to draw it on a blank periodic table. Also remember hydrogen as the exception: it is on the left but is a non-metal.

For periodic table structure and trends, see arrangement and trends. The transition elements page covers the large block of metals in the centre.