Atoms and Elements

Atoms and Elements

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 Neutron has a electrical charge 0, Electrons have a relative charge of -1.

2. Atom

   • All substances are made of tiny particles called atoms.

3. Elements

   • An element is a substance that is made of only one sort of atom. There are about 100 different elements
   • The elements in a group have similar properties to each other.

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

5. Metals and Non-metals

   • Metals
     • The metals are shown on the left of the periodic table.
   • Non-metals
     • The non-metals are shown on the right.

6. Atomic structure

   • 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.

7. Mass Number

   • The mass number of an atom is the total number of protons and neutrons it contains. The mass number of an atom is never smaller than the atomic number. It can be the same, but is usually bigger.

8. Atomic Number

   • 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.

9. Electronic structure

   • The electrons in an atom occupy energy levels. These are also called shells. Each electron in an atom is found in a particular energy level. The lowest energy level (innermost shell) fills with electrons first.

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