Identifying an Ionic Compound. Objectives: To learn and test for metal ions and non-metal ions and then apply them to discover the identity of an unknown ionically bonded substance
Identifying an Ionic Compound- Introduction Ionic compounds are defined as being compounds where two or more ions (an atom or group of atoms with an overall electrical charge) are held next to each other by electrical attraction. One of the ions has a positive charge - called a "cation", and the other has a negative charge - called "anion". Cations are usually metal atoms and anions are either nonmetal or polyatomic ions (ions with more than one atom). Usually, when we have ionic compounds, they form large crystals that you can see with the naked eye. Table salt is one of this- if you look at a crystal of salt, you can see that it has in irregular cube shape. This is because salt likes to stack in little cube-shaped blocks. When forming salt, Na readily loses an electron and Cl readily gains an electrons so both can become stable. Heat is added in the reaction so Na burns brightly in CL gas and a white solid forms on the sides of the container. This solid is salt, or sodium chloride. When the chlorine atom gained an electron, the atoms arrange themselves in a lattice. The force of attraction between a cation and anion is a very strong bond called an "ionic bond". This is an electrostatic attraction. An ionic bond happens between a metal and a nonmetal. Properties of salts: 0. All ionic compounds form crystals. 0. Ionic compounds tend to have high melting and boiling
Chemistry revision notes. Atomic Structure and Bonding, Electrolysis, Acids and Alkalis.
Atomic Structure and Bonding (F) Atoms, Molecules and Ions. AN ATOM is the smallest particle of an element. They cannot be split into smaller particles in chemical reactions. Iron is made of iron atoms (Fe). Sulphur is made of sulphur atoms (S) A MOLECULE is a small group of atoms joined together. The atoms may be the same (e.g. O2) or different (e.g. H2O). The chemical formula shows the number and type of atoms present. Non-metal compounds are made of molecules: Carbon dioxide contains CO2 molecules Methane (natural gas) contains CH4 molecules AN ION is an atom or group of atoms with an electrical charge (+ or -). Metal compounds such as sodium chloride or copper sulphate contain ions. Sodium chloride is made of Na+ and Cl- ions Magnesium Oxide is made of Mg2+ and O2- ions Note that metals form positive ions while non-metals form negative ions. A solid is represented by (s). e.g. H2O(s) is ice. A liquid is represented by (l) e.g. Fe(l) is molten iron. A gas is represented by (g) e.g. H2O(g) is steam. A solution in water is represented by (aq). Salt dissolved in water is NaCl(aq). You should remember that the common gases are diatomic (have 2 atoms in each molecule). These are Oxygen O2; Hydrogen H2; Nitrogen N2; and Chlorine Cl2. Elementary Particles Atoms are made up of smaller particles called protons, neutrons and electrons. The protons and neutrons
Revision of Atomic Structure
Revision of Chemical Bonding Bonding occurs between elements in order that they can obtain stable 'full shell' (noble gas) electron configurations. Types of bonding: ionic, covalent, metallic Ionic Bonding Transfer of electrons to create charged particles called ions Ionic compounds contain positive and negative ions whose charges balance. Usually found in compounds that contain metals combined with non-metals - electrons are transferred from the metals (to leave positive metal ions) to the non-metals (to create negative ions). e.g. sodium chloride NaCl e.g. magnesium chloride MgCl2 (simplified diagram - only outer shells shown) The ions are held together by the strong electrostatic attraction between opposite charges. In the solid they form giant regular structures called lattices. Greater charges generally means stronger forces, so MgO (Mg2+ O2-) has a higher melting point than NaCl. Properties of ionic compounds: Usually solid at room temperature with high melting points and boiling points. Usually hard Usually soluble in water Do not conduct electricity when solid, but can when molten or in aqueous solution because the ions are free to move. Covalent Bonding Sharing of electrons between atoms. Usually between non-metal atoms. Atoms overlap outer shells to create stable full shells. e.g. hydrogen H2 Shared pair of electrons is known as a single covalent
The Periodic Table - Revision Notes The numbers in italics are the page numbers of where more information can be found in the revision guide.
CD6 The Periodic Table Revision Notes The numbers in italics are the page numbers of where more information can be found in the revision guide. Elements and atom 6 Everything is made up of 100 different chemicals called elements . An element is a pure substance that is only made up of one type of particle called an atom. Each element has its own symbol on the periodic table. Eg Copper = Cu Oxygen=O An atom is made up of two parts. In the centre there is a small , heavy lump with a positive charge called the nucleus. On the outside small light ,negatively charged particles called electrons orbit around the nucleus. Nucleus (+ve) Electrons (-ve) An Atom Each element has two numbers on its symbol. The smaller number is the atomic number and tells you the number of protons in the nucleus of an atom of that element. The larger number is the atomic weight (Ar) . The atomic weight tells you the total number of neutrons and protons in the nucleus. Eg 23 Na The atomic number is 11 . The atomic weight (Ar ) is 23. 7 11 Isotopes are two different atoms of the same element that are only different because they have different
