HKNIC - What is an Atom
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What is an Atom
We can imagine that the things we see and touch in our daily life can be broken down or divided into ever smaller parts. But we can also suppose that there must come a point when they are so small that they are no longer divisible.
What is an Atom

This idea was current several centuries BC in India and Greece,.   Indeed, the word "atom" comes from the ancient Greek, meaning "unbreakable."   By the early 19th century, it was observed through chemistry that there are many kinds of atoms, which people at the time believed could not be created or destroyed.  Atoms of the same kind began to be grouped into what are known as elements – the basic "building blocks" of chemical substances.  When our idea is found to agree with what we have observed, it becomes a useful idea.

Elements exist all around us. The air that we breathe, for example, is made up of several of gases: nitrogen, oxygen, carbon dioxide, water vapour and small amounts of other gases. We cannot divide nitrogen or oxygen. But we can divide carbon dioxide into carbon and oxygen, and water vapour into hydrogen and oxygen. So carbon dioxide and water vapour are not elements whereas carbon, hydrogen and oxygen are.

We have now discovered as many as 117 elements since work first began on their identification in the 19th century. Some occur naturally, such as gold. Although gold is rare, if we are lucky enough, we can find it in small nuggets in river beds. Some elements prefer to combine with other types of elements, such as iron which prefers to combine with oxygen in the air to become ferric oxide, commonly known as rust. Elements may occur as gases, such as helium, which is used to fill up balloons; or as liquids, such as the mercury once used in thermometers; or as solids, such as the aluminum in soft drink cans or the body of an aeroplane.