Atomic Structure, Formulae and Elements/Compounds/Mixtures
Atoms and molecules are very different; atoms are the smallest particles of an element that consist of electrons surrounding a nucleus that contains protons and neutrons; molecules are a group of two or more atoms chemically joined together forming an identifiable unit which retains the properties and composition of the substance. Elements are made up of atoms. We can identify the size of each particle in an atom by its relative atomic mass, where one RAM is equal to 1/12 of the mass of a carbon-12 atom. Other elements are measured relative to this mass. There are no units of this.
| Particle | RAM | Charge |
|---|---|---|
| Proton | 1 | +1 |
| Neutron | 1 | 0 |
| Electron | 1/1840 | -1 |
Key Definitions:
Atomic Number is the number of protons in the nucleus of an atom
The mass number is the sum of the number of protons and neutrons in the nucleus of an atom
Isotopes are atoms of the same element containing the same number of protons and electrons, but different numbers of neutrons (same atomic number, different mass number)
Relative Atomic Mass is the weighted average mass of one atom of an element, taking into account the abundance of all the isotopes of an element. It’s measured as a ratio of 1/12 of the mass of an atom of carbon-12
Calculating RAM is from the mass number the relative abundances of all of the isotopes of an element. The equation for this is (mass of isotope 1 * % of isotope 1) + (mass of isotope 2 * % of isotope 2) + (mass of isotope 3 * % of isotope 3) etc.
When writing chemical equation