All matter in the universe is made up of chemical elements. At the time of writing, there are 118 elements have been confirmed to exist and scientists believe there are even more that are yet to be discovered. As the periodic table contains so many elements scientists investigated how the elements were related to each other and how they should be organised. From this research, the periodic table of elements was created. Within the periodic table itself we can generally see that elements are broadly divided into two groups; metals and non-metals.

For instance, the air in the Earth's atmosphere is made out of a mixture of molecular nitrogen and oxygen, plus a trace amount of other elements. While alloys such as brass are made up of a combination of copper and zinc. The atmosphere contains an overwhelming ratio of non-metals to metals, while pure alloys contain only metal. In this article, we will be exploring the properties and characteristics of both metals and non-metals.

• Firstly, we will explore the definition of metals and non-metals.
• We will then study the characteristics of metals and non-metals by studying their differences.
• Afterwards, we will then investigate different elements and determine whether they are metals or non-metals.
• Finally, we will go through some practice questions you might see in your exams.

Metals and non-metals definition

As previously mentioned, elements are divided into two broad categories; metals and non-metals.

A way in which we can differentiate between a metal and a non-metal is by analysing the way they behave in a chemical reaction. Elements try to achieve better stability by having a full outer shell of electrons.

They can do this in two ways:

1. by gaining electrons,
2. by losing electrons.

Elements that lose electrons in chemical reactions end up forming positive ions are metals. While the elements that do not form positive ions, instead gain electrons to form negative ions. Furthermore, elements in group 0 (which already have a full outer shell of electrons) exhibit the properties and characteristics of non-metals too.

Nevertheless, there can be exceptions. Some elements have the characteristics of elements from metals and non-metals. These types of metals are called metalloids or semi-metals.

In the periodic table, we have a general trend. As you move across the period from left to right on the periodic table the metal characteristics of elements decrease. As you go down a group, the metal characteristics of elements increase.

Characteristics of metals and non-metals

Now that we know what metals and non-metals are let us explore the difference between the two. We can start by looking at their electron configurations. Metals of a low atomic number will generally have 1-3 outer shell electrons and non-metals will have 4-8 outer shell electrons.

Let's move on to bonding, metals bond through metallic bonding via the loss of the outer electrons. Non-metals use other types of bonding such as covalent bonding, where electrons are instead shared between atoms in molecules.

In terms of conductivity, metals are very good conductors of electricity but non-metals are bad conductors of electricity.

Let's move on to how metals and non-metals react chemically with a couple of common substances. When reacting with oxygen, metals form basic oxides with some being amphoteric. Non-metals form acidic oxides which can sometimes be neutral. In addition, metals can readily react with acids, whereas non-metals tend to not react with acids.

Looking at the physical properties of metals on metals and non-metals. Metals tend to be shiny, are solid at room temperature (apart from mercury), are malleable, ductile and have a high melting and boiling point. On the other hand, non-metals are dull and do not reflect light, their states at room temperature vary, they are brittle and have relatively low melting and boiling points.

Fig. 3 - A bundle of copper wire. It is malleable and ductile, therefore exhibiting the characteristics of a metal.

Table. 1 - Characteristics of metals and non-metals

Metal and non-metal elements

So we have discussed what metals and non-metals are, and their characteristics. But which elements are metal and non-metals? Let us explore a few common examples.

Oxygen

Oxygen is a non-metal and has the chemical symbol \(\ce{O}\). It is one of the most common elements found on earth and the second-most abundant element in the atmosphere. Oxygen is an important element as it is required for the survival of both plants and animals. Oxygen is not found by itself, rather scientists have to separate it from other elements. Oxygen has two allotropic forms (diatomic and triatomic) that occur in nature, molecular oxygen \(\ce{O2}\) and ozone \(\ce{O3}\).

By itself, oxygen is colourless, odourless and has no taste. Oxygen has many practical applications. For example, animals and plants require oxygen to carry out respiration which produces energy. Oxygen is also used in manufacturing and fueling rocket engines.

Carbon

Fig. 4 - A synthesised diamond, which is an allotropic form of carbon.

Carbon is also a non-metal and has the chemical symbol \(\ce{C}\). Carbon is another element that is important for life. Virtually all molecules in all living organisms contain carbon as it can readily form bonds with many other types of atoms, which allows the flexibility and function that most biomolecules require.

Carbon is allotropic and can exist as graphite and diamonds, which are both valuable materials. Also, substances that have large amounts of carbon, like coal, are burned to provide us with energy to power our daily lives, these are known as fossil fuels.

Aluminium

Aluminium is a metal and has the chemical symbol \(\ce{al}\). Aluminium is one of the most abundant metals on earth. It is lightweight and its metallic properties allow it to be used in a variety of industries such as transportation, building and more. It is key to how we live our modern-day lives.

Magnesium

Magnesium is a metal and has the chemical symbol \(\ce{Mg}\). Magnesium is another metal that is lightweight and abundant. Like oxygen, magnesium is not found by itself. Rather, it is usually found as a part of compounds in the rocks and soil. Magnesium can also be used to separate other metals from their compounds, as it is something called a reducing agent. As it is not very strong, it is often combined with other metals to make alloys to become more useful as a construction material.

Metals and non-metals examples

We have so far explored the definition of metals and non-metals, their different characteristics and some examples of their elements and their uses. Let us consolidate our knowledge and answer some practice questions.