Video Transcript
Which of the following properties is not commonly associated with a metal? A) Ductility. B) Brittleness. C) Malleability. D) Electrical conductivity. Or E) Shininess.
The question asks us for a property not commonly associated with a metal. In chemistry, the simplest definition of a metallic element is one that forms positive ions and exhibits metallic bonding. If you take a look at your periodic table, the more to the left and down in the periodic table an element is, the more likely it is to be metallic.
Metals generally form positive ions in a sea of delocalised electrons. The crystalline arrangement of the ions and the attraction between the ions and the sea of delocalised electrons gives rise to many of a metal’s physical properties.
Ductility can mean the ability of a material to be formed into a thin wire. More generally, ductility means the ability of a material to deform plastically. Plastic deformation is a permanent change of shape due to stress. Metals are well-known for their ductility, being drawn into electrical wires or supporting cables. Therefore, as ductility is commonly associated with a metal, it is not a correct answer.
Brittleness is the tendency for material to break without plastic deformation. Therefore, ductility and brittleness are opposites. Most metals are not brittle at room temperature although some become brittle when cooled significantly. Therefore, brittleness is not commonly associated with a metal and is the correct answer. Just to be safe, I’m going to go through the other options.
Malleability is the ability of a material to be reshaped by hammering. As with ductility, metals are well known to be malleable. The crystalline structure of the ions combined with a strong general attraction to the delocalized electrons allows the material to reform without breaking up. An example where a metal demonstrates its malleability is forging, for instance iron forging. Therefore, malleability is not a correct answer.
Electrical conductivity is the ability of a material to permit an electrical current to flow. Metals have delocalised electrons due to the metallic bonding. These electrons can move from ion to ion and respond to an external electrical field allowing a current to flow. Therefore, electrical conductivity is not a correct answer.
Shininess is another way of describing reflectivity. Reflectivity is strongly related to the smoothness of a surface. Metals can be polished, and so they are commonly shiny. This specific metallic sheen arises because of complex interactions between light and the delocalized electrons. Shininess is very strongly associated with metals and, therefore, is not a correct answer.
So of the five options given, the property not commonly associated with a metal is brittleness.
