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

Ions and compounds

pH strips

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...

Questions & Answers

Questions & Answers Question about acetate buffer and what happens when HCl is added to such a solutionDebra ask:How do I attack this problem?I want to compare the effect of adding 1mmol of HCL to 100 ml of 0.2M acetate buffer at two different starting pH's. (pKa of acetate buffer =4.7Initial pH = 4.7Initial pH = 5.7Thank youHi Debra,There is bo...

Acids and bases - Broensted-Lowry definition

Acids and bases - Broensted-Lowry definition A more fundamental definition of acids and bases than the one provided on the index page was given by the Danish chemists Johannes Broensted. The definitions are:A Broensted acid is a proton doner.A Broensted base is a proton acceptor. The English chemist, Thomas Lowry, proposed exactly the same at roug...


Buffers BackgroundAs shortly explained in the section about how to calculate pH in a solution of dissolved NaHCO3 abuffer has the capability of keeping pH within a certain and narrow range even if an excessof hydrogen ions H+ or hydroxide ions OH- are added.In this particular page I will elaborate a bit on why buffers actually have the capabilities ...