chemistry c3-c4

• All substances are made of tiny particles called ATOMS.
• Substances that contain only one type of atom are called  ELEMENTS.  
• Atoms of different elements can join together to form COMPOUNDS.  
• • Atoms are made of a tiny NUCLEUS surrounded by shells of   ELECTRONS .
• Many common compounds are made up of a metal and one or more non-metals bonded together. The periodic table can be divided into metals on the left and non-metals on the right.
• • The first part is often a metal element, and the second part is usually a non-metal, with the ending ‘-ide’. 
  • An example is magnesium oxide.  
• • Many compounds are made of three or more elements. Often, one of these elements is oxygen. 
  • The names of many of these compounds have an ‘-ate’ ending, for example copper sulphate (CuSO4).
• All matter is made up of particles called atoms.

  These atoms are made up of 3 types of even smaller sub-atomic particles.

  These are called protons, electrons, and neutrons.
• Protons are positively charged

  Electrons are negatively charged
• Neutrons have no charge but 

  help stop the protons in the 

  nucleus from pushing apart
• electronic configuration 2.8.8
• the top number= protons and neutrons (mass number)

  
• the bottom number=protons (atomic number)

  
• group (verticle) = The group number is the same as the number of electrons in the outer shell 

  
• The period number is the same as the number of electron shells the atom has
• Atoms which have full (or empty) outer shells are more stable than those which still have space for more electrons.
• When an atom loses or gains electrons it becomes an ion.

  Ions do not have equal amounts of protons and electrons, so they have an overall charge.

  Proton numbers never change when ions form.
• Metals lose electrons to form positive ions called cations (there are now more protons than electrons, so the ion is positive).  Metals lose electrons from the outer shell to gain the electronic configuration of the nearest noble gas (group VII).  

  
• Because all elements in a group have the same number of outer electrons, they will all end up with the same ionic charges.
• The charge on an ion is written as a superscript (a small symbol to the top right of the atomic symbol).

  E.g.  Ca2+, Li+, O2-, F-

  If the charge is plus or minus one then you don’t need to include the number.
• representing ions-Metal ions keep the same name as their atoms.

  Non-metal ions change the end of their name to -ide.

  Oxygen becomes oxide

  Fluorine becomes fluoride etc
• may come across Polyatomic ions

  
• Metals form positive ions by giving away electrons to empty their outer shells.

  Non-metals form negative ions by receiving electrons to fill their outer shells.

  A strong electrostatic attraction called an ionic bond forms between oppositely charged ions.
• All ionic compounds are solids at room temperature. 
• •  When non-metal atoms combine to form molecules they do so by sharing electrons in their outside shells, this is called a covalent bond.  
  •   A covalent bond is an electrostatic attraction between the two positively charged nuclei and the shared pair of electrons in the covalent bond.  
• Atom - a particle with equal amounts of protons and electrons

  Ion - a charged particle with unequal amounts of protons and electrons

  Molecule - 2 or more atoms covalently bonded together