atomic struc/ periodic table

• Everything whether it's living, non-living or even a cell itself is made up of lots of tiny particles which we call atoms
• A single cell probably contains more than 100 trillion atoms
• Atom


  Basic structure is a central nucleus surrounded by electrons which orbit around the nucleus in rings that we call shells
• Particles that make up the nucleus


  • Protons
  • Neutrons
• Protons and neutrons


  • Have the same mass, with a relative mass of 1
  • Protons have a positive charge of 1+
  • Neutrons have no charge (are neutral)
• Electrons

  • Have a mass 2000 times smaller than protons and neutrons
  • Have a negative charge of 1-
• The size of an atom depends on which element it is
• Atoms have a radius of around 0.1 nanometers
• Most of an atom is actually empty space
• The nucleus is 10,000 times smaller than the width of the atom
• Electrons are even smaller than the nucleus
• Atom with 3 protons and 3 electrons


  Overall the atom is neutral as the positive and negative charges balance out
• Ion


  An atom that has lost or gained electrons, so the positive and negative charges no longer balance
• Negative ion

  • An atom with more electrons than protons, resulting in a 1- or 2- charge
• Positive ion


  • An atom with more protons than electrons, resulting in a 1+ charge
• The periodic table represents different types of atoms, which we call elements
• Nuclear symbol


  Provides information about an element, including the elemental symbol, atomic number, and mass number
• The atomic number tells us the number of protons in the atom, which determines the element
• The mass number tells us the total number of protons and neutrons in the atom
• The number of electrons in an atom is always equal to the number of protons
• Atom


  Central nucleus comprising protons and neutrons, with electrons orbiting the nucleus
• Protons


  Determine which element the atom is
• Hydrogen


  • Smallest element, with 1 proton and 1 electron
• There are around 100 different elements
• Periodic table


  Organizes elements, each box represents a different element
• Nuclear symbol


  Represents an element
• Atomic number


  Unique number representing the number of protons in an element
• An atom with 3 protons cannot be carbon, it must be the element with atomic number 3, which is lithium
• Element symbol


  One or two letter symbol representing the element name (e.g. C for carbon, Li for lithium)
• Some element symbols are more confusing (e.g. sodium is Na, iron is Fe)
• Isotopes


  Different forms of the same element that have the same number of protons but a different number of neutrons
• Relative atomic mass


  The average mass of all the isotopes that make up a particular element
• Calculating relative atomic mass


  1. Multiply each isotope's abundance by its mass

  2. Sum the results

  3. Divide by the sum of the abundances of all isotopes
• The relative atomic mass of copper is 63.6
• Molecule


  A group of two or more atoms that are held together by chemical bonds
• Molecules


  • Oxygen
  • Water
  • Nitrogen
  • Chlorine
  • Carbon dioxide
• Compound


  A substance that contains two or more different elements, with the atoms held together by chemical bonds
• Molecules


  Can contain multiple different elements
• Helium


  Exists as a single atom, so it is not a molecule
• Compounds always contain two or more different elements