topic 1 chem

• atoms contain a centeral nucleus surrounded by electrons
• atoms have no overall charge, elements and protons have the same charge
• smaller number on an element = atomic number = number of protons and electrons
• bigger number = the mass number
• neutrons = mass number - atomic number
• protons, neutrons, electrons = isotopes
• isotopes are atoms with the same element with different numbers of neutrons
• ions are atoms which have an overall charge, ions have lost or gain electrons
• positive ions = lost electrons
• negative ions = gains electrons