Kaizen Education

Atoms are like Lego

Every substance in the universe is made up of building blocks known as atoms. There are only about 100 types of atoms but they can be arranged in different combinations to create countless types of different substances. In this way, atoms are like tiny pieces of Lego.

Unlike blocks of Lego, atoms are round like tiny balls. They are so small that they cannot be seen with even the most powerful optical microscope. Instead, scientists must use a scanning tunneling microscope (STM) to obtain images of atoms such as the copper atoms.

Elements

Elements are substances that are made up of just one type of atom. The air you breath is not pure but is a mixture of different elements.Most of the air you breath is made up of nitrogen. Billions of invisible oxygen and nitrogen atoms surround you. They are what you feel hitting your skin on a windy day.

Each element has a unique set of characteristics that scientists refer to as its properties.

These properties determine whether an element is classified as metallic or non-metallic.

Metallic elements

Aluminum, iron, mercury, gold and solver are all examples of metallic elements that are used everyday in construction, electronics and jewellery. Your body needs metals too- iron, calcium, sodium and potassium are all needed for it to function properly. Metallic elements all share some characteristic properties. Metals:

• Tend to be shiny (this is known as being lustrous)

• are solid at room temperature (except mercury, which is a liquid)

• are good conductors of heat and electricity, allowing heat and electricity to flow easily through them

• can be bent and hammered into sheets (when metals act this way, there are refereed to as being malleable)

• can be stretched into wires (metals are referred to as being ductile)

   

Non-metallic elements

Non-metallic elements tend to be solids or gases at room temperature. Bromine is the only non-metal that is liquid at room temperature. Some non-metallic elements are shown below. Non-metals:

• Tend to be dull (not shiny)

• Do not conduct heat or electricity

• break or crumble when you bend them (non-metals are refereed to as being brittle)

   

The black ask or charcoal formed when you burn paper or wood is made of the element carbon, and is typically of non-metallic solids. The element helium is a non-metallic gas that is light and non-toxic and can be used safely in party balloons.

There are 118 known elements but only 98 of these occur naturally- the rest are synthetic and must be made in a lab. Each element has a name and a chemical symbol.

Chemical symbols

Often the chemical symbol of an element comes directly from its name. For example, the element calcium is given the symbol Ca, carbon has the symbol C and magnesium has the symbol Mg. However, sometimes the symbol of an element does not appear to relate to the name at all. For example potassium has the symbol K and sodium has the symbol Na. This is because their symbols come from the names for the elements in other languages. These names may be different from those used in English. For example, the Latin name for potassium is kalium.

Writing chemical symbols

The chemical symbol of an element is usually made of one or two letters.

• The first letter is always in upper case
• the second letter is always in lower case

So the chemical symbol for chlorine is always written as Cl and never CL or cl. Likewise, sodium is Na and not NA or na.

The last six elements of the periodic table are so radioactive that they have not yet been absolutely proved to exist. Until their existence is confirmed, these elements are given temporary symbols of three letters.

Atoms in elements

Elements are made up of just one tyoe of atom. However, the atoms in elements can be arranged in different ways.

The atoms can exist:

• as single atoms (this is referred to as being mono atomic)
• in clusters of atoms called molecules
• in large grid-like structures called lattices

The way the atoms are arranged in an element determines many of the physical properties of the element. Physical properties include whether the element is solid, liquid or gas, its melting and boiling points, how well it conducts heat or electricity, and if it blends or breaks when a force is applied.

Mono-atomic elements

An elements that consists of just single atoms is known as mono-atomic. Mono-atomic elements are rare, with only six of the 98 naturally occurring elements being mono-atomic. These are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). These elements are all non metallic gases.

• The oxygen you’re breathing right now is made up of billions of oxygen molecules. Each oxygen molecules two oxygen atoms. For this reason scientists represent oxygen gas by the molecular formula O2.
• Other non-metallic elements that are made up of molecules with just two atoms are nitrogen (N2), hydrogen (H2) and chlorine (Cl2)
• Some non-metallic elements are made up of molecules with more than two atoms. For example, phosphorus commonly has four atoms, giving it the molecular formula P4.
• Sulfur forms ring shaped molecules of different sizes. One ring has just six sulfur atoms (with a molecule formula S6) while other rings contain eight sulfur atoms (S8) and 20 sulfur atoms (S20)
• Carbon is unique among the non-metallic elements in that it can form very large molecules of almost any size. The most famous is called the buckyball. This is a molecule that has 60 carbon atoms arranged in the shape of a soccer ball and has the molecular formula C60.

Elements in lattices

Crystal lattices are large grid-like structures that repeat the same arrangement of atoms over and over. All metallic elements form crystal lattices. Only a few non-metallic elements for crystal lattices.

Metallic lattices

Eighty per cent of the known elements are metals. The atoms in metals form lattices, rather than molecules. The lattice structure makes metals dense, strong and solid at room temperature. The only exception is mercury, which is a liquid at room temperature. As a result, metals are important materials for the construction and manufacture of a large variety of objects- from buildings and bridges through to trains, planes, cars, tools and jewellery.

The atoms in metallic lattices can slide and move over each other without breaking the lattice. This means that metals can be bent, drawn into thin wires or hammered into thin sheets. Metal sheets can be thick, like the ones used to build a corrugated iron shed. Or the sheets can be very thin, like aluminum foil.

Non-metallic lattices

Only a few non-metallic elements form lattices. An example is silicon. Another example is carbon, which forms crystal lattices to make graphite and diamond.

In graphite, the carbon atoms form sheets that are stacked on toip of each other. The sheets do not break easily but can slide across each other. This makes graphite a good lubricant for industrial machinery. The lead in grey-lead pencils is also made of graphite mixed with clay.