Atomic structure

• Atom


  smallest part of an element
• Molecule 


  made of a fixed number of atoms covalently bonded together
• what is the mass and charge of a proton

  mass = 1 charge = +1
• What is the mass and charge of a neutron

  mass = 1 charge= 0
• what is the mass and charge of a electron

  mass= too small charge= -1
• Atomic number

  the number of protons in an atom
• Mass number

  The number of protons and neutrons in an atom
• Isotopes

  Atoms of the same element but with a different number of neutrons
• Relative atomic mass (Ar)

  the average mass of an atom
• calculating Ar

  multiply the mass of each isotope by its relative abundance , add those together , divide them by (usually)100
• columns are called groups
• Rows are called periods
• Metals on the left
• Non-metals on the top right + hydrogen
• Elements in the same group have the same number of electrons in their outer shell
• Electrons in the same group have similar chemical properties because have the same number of electrons on their outer shell
• Noble gases are unreactive because they have a full outer shell of electrons