Chemistry

Elements, compounds and mixtures An element contains only one type of atom. A compound contains atoms of two or more elements chemically bonded in fixed proportions. A mixture contains two or more substances that are not chemically bonded. Its components can be separated by physical methods. Atomic structure Particle Relative charge Relative mass Location Proton $+1$ $1$ Nucleus Neutron $0$ $1$ Nucleus Electron $-1$ $\frac{1}{1840}$ Shells around nucleus The proton number, or atomic number, is the number of protons. The mass number, or nucleon number, is the total number of protons and neutrons. In a neutral atom, number of electrons equals number of protons. ...

Solids, liquids and gases State Arrangement and separation Motion Macroscopic properties Solid Particles closely packed in a regular arrangement Vibrate about fixed positions Fixed shape and volume; almost incompressible Liquid Particles close together in an irregular arrangement Move and slide past one another Fixed volume; takes container shape; almost incompressible Gas Particles far apart in a random arrangement Move rapidly and randomly in all directions No fixed shape or volume; easily compressed; low density These descriptions apply to particles, not necessarily individual atoms. A particle may be an atom, molecule, or ion. ...