bonding

• Ionic bonding occurs when one atom transfers electrons to another atom, resulting in the formation of positive and negative ions.
• The three states of matter are solid, liquid and gas.
• Melting and freezing between solid and liquid take place at the melting point.
• Boiling and condensing between liquid and gas take place at the boiling point.
• The amount of energy needed to change state from solid to liquid and from liquid to gas depends on the strength of the forces between the particles of the substance.
• The nature of the particles involved in the three states of matter depends on the type of bonding and the structure of the substance.
• High- because of many strong covalent bonds between atoms in giant structure.
• Diamond and sand are poor because electrons can’t move.
• Conductivity when molten is poor because ions can’t move.
• Graphite is good because free delocalised electrons can move through the structure.
• Conductivity when solid is poor because ions can’t move.
• High- strong electrostatic forces between positive ions and delocalised electrons.
• The stronger the forces between the particles, the higher the melting point and boiling point of the substance.
• Limitations of the simple model include that there are no forces between the spheres, and that atoms, molecules and ions are solid spheres.
• The three states of matter can be represented by a simple model where particles are represented by small solid spheres.
• Particle theory can help to explain melting, boiling, freezing and condensing.
• Gas particles are widely spaced and in constant motion, with frequent and elastic collisions.
• Liquids particles are closely spaced but still in constant motion, and therefore are constantly colliding.
• Solid particles can only vibrate in a fixed position.
• Pure elements and compounds melt and boil at specific temperatures.
• Melting point and boiling point data can be used to distinguish pure substances from mixtures.
• A pure substance will melt or boil at a fixed temperature, while a mixture will melt over a range of temperatures and not have a sharp melting point.
• A pure solid will melt at a fixed temperature and the line will stay horizontal when it is melting, with the heat absorbed to break the bonds between the solid particles.
• Solid starts melting at a certain point, after which the temperature will start to rise again when all the solid has melted.
• In chemical equations, the three states of matter are represented as (s), (l) and (g), with (aq) for aqueous solutions.
• Metal atoms lose electrons to become positively charged ions, while non-metal atoms gain electrons to become negatively charged ions.
• When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and so charge can flow.
• Some common groups of elements have a charge, these are called compound ions.
• When in solid form, ionic compounds do not conduct electricity because the ions are fixed in place.
• Ionic compounds have high melting points and high boiling points due to the large amounts of energy needed to break the many strong electrostatic forces of attraction between oppositely charged ions.
• Group 1 elements form +1 ions such as Na + , Group 2 elements form +2 ions such as Mg 2+ , Group 6 elements form -2 ions such as Mg 2+ , and Group 7 elements form -1 ions such as F -.
• Covalent bonding occurs in non-metallic elements and in compounds of non-metals.
• Lithium Oxide has Li + ions and O 2- ions.
• When atoms share pairs of electrons, they form covalent bonds.
• The empirical formula is the simplest ratio of ions in a compound.
• To work out the formulae of compounds, ions are combined together so that the total positive charge of the ions is the same as the total negative charge of the ions, resulting in a neutral compound.
• MgF 2 is the formula for Magnesium Fluoride, which requires two F- ions to cancel out the +2 charge on the Mg.
• Covalently bonded substances may consist of small molecules, such as H 2 , Cl 2 , O 2 , N 2 , HCl, H 2 O, NH 3 and CH 4.
• An ionic compound is a giant structure of ions held together by strong electrostatic forces of attraction between oppositely charged ions.
• The intermolecular forces increase with the size of the molecules, so larger molecules have higher melting and boiling points.