ATOMS

ATOMS

1. Remember

   • There are two types of electric charge: a positive charge and a negative charge. Electrical charges of the The same type repel each other. Opposite electrical charges attract each other.

2. All matter is made up of atoms. (There are smaller particles)

3. Inside the atom

   • we can find three different particles:
     • Electrons: Negative (-) , Negligible
     • Protons: Positive (+), Similar to a hydrogen atom
     • Neutrons: Neutral, Similar to a hydrogen atom

4. What does an atom look like?

   • Atoms are made up of electrons and the nucleus is made up of protons and neutrons.

5. Representing atoms

   • We use atomic parameters to summarise the information related to the internal composition of an atom: The atomic number (Z) and the mass number (A)

6. Isotopes

   • Atoms with the same number of protons but a different number of neutrons are called isotopes.

7. IONS

   • Atoms are not always neutral. They can gain or lose electrons in a process called ionisation. When atoms are ionised they become ions.

8. The organisation of atoms in matter

   • All matter is made up of chemical elements.Chemical elements are organised in the periodic table according to their atomic number.Can be classified in:
     • Simple substances
       • Single atoms: This organisation is made up of single atoms with no bonds between them.
       • Large clusters: Atoms are all bonded to each other.
       • Molecules: Two or more atoms of the same type bond together.
     • Compound substances
       • Molecules. Atoms of different types bonded together.
       • Ionic crystals or compounds: Ions with different charges attract each other, the ions bond together. An ion attracts all surrounding atoms with the opposite electric charge, so they form clusters called ionic crystals or compounds.

9. Chemical reaction

   • A physical change is a transformation that affects the form of a substance, but not its composition.
   • A chemical change is a transformation that changes the composition of matter.Chemical changes are called chemical reactions.

10. Chemical equation. A chemical reaction is represented by a chemical equation.

    • Reactants are the initial substances which, when mixed together, start a chemical reaction.
    • Products are the new substances that form as a result of the chemical reaction between the reactants.

11. Energy in chemical reactions

    • A reaction is exothermic when thermal energy is produced or released when it occurs.
    • A reaction is endothermic when thermal energy is required to produce it.