Ions and compounds

Atoms are made up of neutrons that are neutral and have no charge, protons with a positive charge andelectrons with a negative charge.

An ion is an entity or a group of atoms with a positive or negative charge such as the positively charged hydrogen ion H+ and thenegatively charged nitrate ion NO3-. Negatively charged ions are also called anions while positively charged ions are called cations.

A compound is something that is made up oftwo or more simple substances. Ammonia NH3 is a compound without a charge.

Atom model

Below it is shown how positively charged protons (yellow) and neutral neutrons constitutes a nucleusin the atom while the negatively charges electrons orbits the nucleus. This is a very simple model of the atom.A more complicated model would include a nucleus surrounded by orbitals with electrons in them orbiting the nucleus.

Web resources

A philosophical approach to atoms
A full course about atoms and ions
Encarta - encyclopedia

pKa and Ka Background informationThe Ka value is a value used to describe the tendency of compounds or ions to dissociate. The Ka value is also called the dissociationconstant, the ionisation constant, and the acid constant.Topic: Equilibriums The pH scale The ...

NaHCO3 dissolved in water - how is pH calculated? Background about buffersA buffer is a solution that has the ability to keep pH within a certain and narrow range: even if an excessof hydrogen ions (H+) is applied to the solution. In other words:buffers resist changes in pH whenreasonable amount of either H+ or OH- is added to the buffer solution.Th...

Gases - the ideal gas law explained Chemical compounds in aqueous solutions are fairly easy to handle as their quantities can either be expressed in weight such as grams or kilos, moles perliter (molarity) or moles per kg (molality).Topic: pKa & Ka The basics ...

pH strips Background Substances with the property to change color when they come into contact with an either acidic or basicsolution are called pH indicators. This is used in pH strips that changes color when they come into contactwith hydrogen ions (H+) and hydroxide ions (OH-). Usually, pH strips are b...