Alkali earth metals Inert metals
covalent bonding: sharing 2 or more electrons in the atoms of the compounds’ outer shells, the elements involved in these types of bonding are usually non-metals; this happens so that both elements are energetically stable, covalent bonds are formed because of the mutual attraction of the positive charge of the atoms’ nuclei and the negative charge of their electrons.
chemicals that bond using covalent bonding are usually gases or liquids at room temperature. e.g. Elements: chlorine (Cl), hydrogen (H) Compounds water (H2O), Hydrogen chloride (HCl), Ammonia (NH3).
Covalent bonding in elements:
Name: hydrogen Name: Chlorine
Symbol: H 1 Symbol: Cl 2,8,7
Relative atomic mass: 1 Relative atomic mass: 35
Atomic number: 1 Atomic number: 17
Covalent bonding in compounds:
HCl, hydrogen chloride
e.g. ammoniaNH3
Name: Hydrogen Name: Nitrogen
Atomic symbol: H 1 Atomic symbol: N 2,5
relative atomic mass: 1 Relative atomic mass: 14
atomic number: 1 Atomic number: 7
e.g. Methane CH4
Name: Hydrogen 1
Atomic symbol: H
relative atomic mass: 1
atomic number: 1
Name: Carbon
Atomic symbol: C 2,4
Relative atomic mass: 12
Atomic number: 6
there can be as many shared pairs of electrons and covalent bonds as the outer shell of the reactant atoms can fit.
Metallic bonding
This type of bonding is found in metals.
for example: Copper (Cu) Sodium (Na) Magnesium (Mg).
Metallic bonding is the attraction of metal ions e.g. Cu 2+ (Copper cation ) and the delocalised electrons. (Opposite charges attract).
Cu2+ e- Cu2+ e- Cu2+ e- Cu2+
Cu2+ e- Cu2+ e- Cu2+ e- Cu2+
Cu2+ e- Cu2+ e- Cu2+ e- Cu2+
Cu2+ e- Cu2+ e- Cu2+ e- Cu2+
Cu2+ e- Cu2+ e- Cu2+ e- Cu2+
To return a compound in to its original reactant elements a chemical reaction is needed.
for example to change water(H2O) to its original elements 2H (2 hydrogen ) and one O (oxygen), one must heat up the compound, once this process has taken place oxygen and hydrogen gas are given off, this is called a reverse reaction where, one can react the elements to gain a compound and then react the compound again to gain the original elements. during some reverse reactions once the point of equilibrium is reached no more reactions will take place.
2H + O (H2O)
Elements are substances made from only one type of atom, these atoms all contain the same number of protons, neutrons and electrons.
compounds are substances made from 2 or more types of elements, and these substances contain two or more types of atoms and they bond through different ways to gain their energetic stability, for example, metallic, ionic and covalent bonding.
mixtures are substances that could be made of either elements or compounds and are combined together, but they are not chemically bonded; for example a mixture of iron and wood, the iron can easily be separated from the wood with out any needs for change in temperature, pressure or any types of chemical reactions by simply using a magnet to lift all the iron out of the mixture.
In a mixture there can be any amount of substances present, for example a mixture of 100 footballs and one baseball, it will not make any difference to the substances present as no chemical reaction is taking place and it will not speed up or slow down an reaction.
Mixtures can also be found in different forms for example oil and water; this is an example of an emulsion mixture, where the 2 compounds are contained in one container but the two do not mix since water is heavier that oil and it sinks to the bottom and the oil floats on the top of the container, this rule applies for any type of water like liquid and any oily liquid, the one that contains oil will always float on top. Even I you shake the container, you will only see for a short time small amounts of oil in the water but those drops will quickly join together and again form the diagram below. Other examples of emulsion are cheese & butter.
Another example is a foam mixture, when a gas is trying to dissolve in liquid like foam, for example if one uses washing up liquid and mixes it with some water then uses a straw to try and blow some air in to the solution, the only thing that will happen is that bubbles will form in the solution but if you try and add some other form of liquid or solid in to the solution like ice or any type of juice they will easily combine with the solution and their reaction will be irreversible.
Aerosol mixtures:
This is the desperation of small solid particles to dissolve in a liquid solution; although these solutions resemble a real compound solution they are not, this can be tested by: shine a light on a sol mixture, although the solid particles are very small they are still able to diffuse parts of the light, this process is called ‘Tyndall’ some examples of a sol mixture are: clay and water mixture.
Gel mixtures:
This is the desperation of small solid particles to dissolve in a liquid solution. Gel mixtures have the same characteristics as a sol mixtures in fact if you add water to a gel mixture it becomes a sol mixture and in reverse if you increase the concentration of solid materials of a sol mixture it will become a gel, solution, the only difference is it’s gelatinous properties and the fact that even though a gel might be gelatinous at room temperature e.g. broth gelatine, if you heat it up it will become liquid, and vice versa but some gel mixtures will not reverse to their original state for example, the white bit in eggs, once the gelatine is heated it will take a solid state and it will not change back to its original state.
