Chemistry

• Mendeleev didn't know about isotopes and so Iodine and Tellurium were reversed in his table.
• An electronic structure is the way in which electrons are arranged in an atom.

  Electrons occupy energy levels, also called electron shells, outside the nucleus.

  The electronic structure of an atom can be predicted from its atomic number.

  Electronic structure of an element is linked to the position on where it is in the table as elements are placed in periods by their increasing atomic number.
• In a metal element's chemical reaction, metal atoms lose electrons to form positive ions.
• What are the properties of metal?

  Shiny,a good conductor of electricity and heat, high density, malleable and ductile.
• What are the properties of non-metal?

  Poor conductor of electricity and heat, dull, low density, brittle
• Most metal oxides are basic and most non-metal oxides are acidic.
• Ions are electrically charged particles that form when an atom or molecule gain or lose an electron.
• Most metals have high melting and boiling points.
• Most non-metals have low melting and boiling points.
• Gain electron = negative ion
• Lose electron = positive ion
• The reactions of elements are related to the number of electrons in their outer shell
• During a reaction, atoms of metal elements give away electrons to form positive ions which are formed with a full outer shell so they are very stable.
• During a reaction, atoms of non-metal elements gain electrons to form negative ions which are formed with a full outer shell, making it very stable.
• An oxide is a compound containing oxygen or oxide ions.
• Oxygen reacts with metal which forms a white oxide.
• The product of a reaction with chlorine is called a chloride.
• Chlorides are a white solid but dissolve in water to form a colourless solution.
• The more easily the ions form, the mire reactive the metal.
• A molecule is a collection of two or more atoms held together by a chemical bond.
• A covalent bond is a bond between atoms formed when atoms share electrons to achieve a full outer shell.
• Ionic bonding forms between two atoms when an electron is transferred from one atom to the other, forming a positive-negative ion pair.
• When a metal reacts with oxygen, it forms metal oxide.