Atoms

Atoms

1. Atoms consist of electrons surrounding a nucleus that contains protons and neutrons. Neutrons are neutral, but protons and electrons are electrically charged: protons have a relative charge of +1 and electrons have a relative charge of -1.

2. All substances are made of tiny particles called atoms. An element is a substance that is made of only one sort of atom. There are about 100 different elements. These are shown in the periodic table, which is a chart with all the elements arranged in a particular way.

   • All substances are made from tiny particles called atoms. An atom has a small central nucleus made up of smaller sub-atomic particles called protons and neutrons. The nucleus is surrounded by even smaller sub-atomic particles called electrons.
   • Protons and electrons have an electrical charge. Both have the same size of electrical charge, but the proton is positive and the electron negative. Neutrons are neutral.

3. The horizontal rows in the periodic table are called periods and the vertical columns are called groups.

4. The elements in a group have similar properties to each other.

5. The metals are shown on the left of the periodic table, and the non-metals are shown on the right. The dividing line between metals and non-metals is shown in red on the table below. You can see that most of the elements are metals.

6. The atoms of each element are represented by a chemical symbol.

7. This usually consists of one or two different letters, but sometimes three letters are used for newly discovered elements.

8. For example, O represents an oxygen atom, and Na represents a sodium atom.

9. The first letter in a chemical symbol is always an UPPERCASE letter, and the other letters are always lowercase.

   • The number of electrons in an atom is equal to the number of protons in its nucleus. This means atoms have no overall electrical charge.
   • The atomic number of an atom is the number of protons it contains. All the atoms of a particular element have the same atomic number (number of protons). The atoms of different elements have different numbers of protons. For example, all oxygen atoms have 8 protons and all sodium atoms have 11 protons.

10. science

11. So, the symbol for a magnesium atom is Mg and not mg, MG or mG.