CHEMISTRY TOPIC 1

CHEMISTRY TOPIC 1

1. Atoms and their structure

   • Atoms are the smallest particle of a chemical element that can exist.
   • 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.
   • Sub atomic particles
     • subatomic particles are particles much smaller than atoms. There are two types of subatomic particles: elementary particles, which according to current theories are not made of other particles; and composite particles.[2] Particle physics and nuclear physics study these particles and how they interact.

2. Isotopes

   • Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom.

3. Chemical equations, subscripts and superscripts

   • A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and formulae, wherein the reactant entities are given on the left-hand side and the product entities on the right-hand side.
   • In chemical formulas the number of atoms in a molecule is written as a subscript, so we write H2O for water which has two atoms of hydrogen for each one of oxygen.
   • In chemical equations, superscripts are used to show the charge of ions of the atoms or molecules. They are placed immediately after the chemical formula with their sign denoting whether it is an anion (negatively charged) or a cation (positively charged).

4. Mixtures and separating mixtures

   • In chemistry, a mixture is a material made up of two or more different substances which are mixed but are not combined chemically. A mixture refers to the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.
   • The individual substances in a mixture can be separated using different methods, depending on the type of mixture. These methods include filtration, evaporation, distillation and chromatography.

5. The periodic table

   • The classic Periodic Table organizes the chemical elements according to the number of protons that each has in its atomic nucleus. The Periodic Table of the Elements arranges all of the known elements in an informative array. Elements are arranged in order of increasing atomic numbe
   • Group 7
     • The halogens. The group 7 elements are placed in the vertical column second from right in the periodic table. Chlorine, bromine and iodine are the three Group 7 elements you are likely to see at school. Fluorine is too reactive to keep or produce safely at school.
   • Group 0
     • The group 0 elements are found on the right hand side of the periodic table. They are called the noble gases because they are very unreactive. The highest occupied energy levels (outermost shells) of their atoms are full: helium atoms have two electrons in their outer energy level.
   • Group 1
     • The Group 1 elements in the periodic table are known as the alkali metals. They include lithium, sodium and potassium, which all react vigorously with water to produce an alkaline solution.

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