For an explanation, see the main splats page
SPLATS about chemical bonds
The principles of chemical bonds
- Molecules are made of atoms linked together by chemical bonds involving valency electrons and they can be measured: molecules have a fixed mass, and a set size.
- We consider matter as made of atoms that are grouped into molecules. We consider atoms as a nucleus surrounded by electrons. The electrons form chemical bonds.
- In 1921, Charles Bury related the electronic structure of elements to their chemistry, setting the scene for others to understand the chemical bond.
- The electrons around the nucleus largely direct chemical properties, as atoms form covalent bonds by sharing electrons or ions by gaining and losing them.
- In 1931, Linus Pauling saw resonance bonding in compounds lacking one single structure and used it to explain the high stability of symmetric planar molecules.
- Chemical change usually involves electron transfer, which requires the application or release of energy as chemical bonds are changed, broken and formed.
- The shape of a molecule can be predicted from our knowledge of its chemical bonds and the sizes and numbers of the atoms involved in forming it.
- Bonding between the atoms in chemical compounds takes different forms: ionic bonds, metallic bonds and covalent bonds being the most common forms encountered.
- Molecules may have ionic or covalent bonds, depending on the affinities of their components for electrons. Gradations between the extremes are also possible.
- Ionic compounds may be considered for calculation and prediction purposes as if they are molecules, even though they never exist in nature as molecules.
- Some substances decompose when heated, because the bonds holding the compound together were overcome by the heat energy that was externally applied.
- Decomposition is a chemical change producing new compounds: compounds may decompose when energy is applied, or when energetic bonds between atoms break down.
- Combustion is a chemical change, usually happening in the presence of oxygen, but it is also able to happen in chlorine, which is an excellent oxidizer.
- Mass is always conserved in chemical reactions: if the products appear to have a different mass, one product was probably lost in the form of a gas.
- One common form of chemical reaction is the redox reaction, where one of the reactants is oxidized and another reactant is reduced at the same time.
- Extracting metal from ore involves reducing the metal from an oxidized state to a neutral state, while the reducing agent is oxidized at the same time.
- Energy affects molecules and ions, leading to change as new linkages and combinations are formed, because the energy is able to influence bonds.
- There is an enthalpy of formation associated with every chemical reaction, and this can be predicted, given sufficient knowledge of the bonds involved.
- Chemical change involves atoms changing partners in either a simple or a complex way to form new compounds. Energy is always involved in chemical changes.
- Most reactions need energy, or else they release energy: an endothermic reaction absorbs energy, while an exothermic reaction releases energy.
- In 1800, William Nicholson and Anthony Carlisle use electrolysis to separate water into hydrogen and oxygen, using the battery of Alessandro Volta.
- Electrolysis is a chemical change, involving the application of energetic electrons to ions, while the electrical energy strips electrons from other ions.
- In 1834, with the increasing use of electrolysis, Michael Faraday introduced the convenient terms electrolyte, electrode, anode, cathode, ion, cation and anion.
- Heating of a substance can bring about chemical change, because heat is a form of energy, and so is able to make changes in the existing bonds.
- Some chemical reactions can produce useable energy, as in the heat produced in a flame, or the electricity produced from chemical energy in a cell.
- The simple structures of many molecules are reflected in their equally simple formulae, but simple formulas can sometimes be misleading if taken literally.
- We can write a molecular formula to represent a compound, but the fact that we use a molecular formula does not imply that such a molecule necessarily exists.
- We can calculate empirical formulae of all sorts of compounds, but just because we use an empirical formula, that does not imply that such a molecule exists.
- We can draw structural diagrams of molecules, but our use of a structural diagram does not imply that such a molecule as the one drawn actually exists.
- Chemical analysis often relies on knowing what chemical changes will happen in given conditions, so that each reaction (or lack of one) provides information.
- The van der Waals forces make atoms cling and stick together, and this is why gases fail to perform in the ideal way laid down by the gas laws.
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