Basic Chemistry/Atoms and elements
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Elements and the Periodic Table
[edit | edit source]Elements contain only one type of atom. They can't be split up into anything simpler. Everything on Earth is made up of elements. There are about 118 different elements, and they are listed in the Periodic Table. Every element has a name and a symbol, for example Carbon, C.
The elements are specifically arranged in the periodic table so that
- every column contains elements with similar properties. Columns are called groups.
- every row shows a gradual change or "trend" in properties across it. Rows are called periods.
- elements are listed by atomic number. (see below)
Atoms
[edit | edit source]The atoms in an element are all identical. All materials are made up of atoms.
Atoms have a nucleus in the middle which is made up of protons and neutrons. Protons are positively charged whereas neutrons are neutral. Electrons spin quickly around the nucleus. They are negatively charged.
Elements
[edit | edit source]Elements are substances that are only made from one kind of atom.It can also be defined as substances that cannot be broken down into simpler substances by physical or chemical changes.These substances are called elements
The Discovery of the Elements
[edit | edit source]Before 1669 the following elements had been discovered: carbon, sulfur, iron, copper, arsenic, silver, tin, antimony, gold, mercury and lead. Some had been known for thousands of years, although they had not been known as elements.