Chemistry Revision Topic 1

Chemistry Revision Topic 1

1. What the atoms are and their structure

   • Atoms are the basic units of matter and the defining structure of elements. Atoms are made up of three particles: protons, neutrons and electrons. Protons and neutrons are heavier than electrons and reside in the center of the atom, which is called the nucleus.
     • Atoms consist of electrons surrounding a nucleus that contains protons and neutrons.
       • Protons
         • electrically charged: +1 relative charge. At the centre of an atom
       • electrons
         • electrically charged: -1 relative charge. Arranged around the nucleus in shells
       • neutrons
         • neutral. At the centre of an atom
   • The number of protons in an atom is called its atomic number. In the periodic table atoms are arranged in atomic number order.

2. Isoptopes

   • Isotopes are atoms of an element with the normal number of protons and electrons, but different numbers of neutrons. Isotopes have the same atomic number, but different mass numbers. The different isotopes of an element have identical chemical properties. However, some isotopes are radioactive.

3. Chemical equations: subatomic particles and coefficients

   • The letter or letters that represent an element are called its atomic symbol. The numbers appearing as subscripts in the chemical formula indicate the number of atoms of the element immediately before the subscript. If no subscript appears, one atom of that element is present
   • the coefficients give the number of molecules (or atoms) involved in the reaction

4. Mixtures

   • The substances in a mixture are separated by the differences in their physical properties, such as their particle size. The more different the properties are, the easier it is to separate the substances
   • The different substances in mixtures are usually easily separated from one another. The method you use depends upon the type of mixture you have

5. Nuclear Model