Atoms

• Isotopes are atoms with different numbers of neutrons but same atomic number
• Atomic number is the number of protons
• Mass number is the sum of neutrons + protons
• Atomic mass is the average mass of all naturally occurring isotopes of an element
• Relative formula mass = sum of relative masses of all elements present in one molecule
• Molecular formula shows how many atoms of each type there are in a molecule
• The mass number is always greater than or equal to the atomic number
• Ions have lost/gained electrons, so they have an overall charge
• The periodic table arranges elements by increasing atomic number, which increases from left to right across rows.
• Isotopes have different numbers of neutrons but same number of protons
• Metals tend to be found on the left side of the periodic table
• Non-metals tend to be found on the right side of the periodic table