atomic structure and bonding

• elements are arranged in the periodic table by increasing atomic number (or increasing number of protons).
• elements in the same group all have the same number of outer electrons, this gives them similar chemical properties (for example how reactive they are).
• Group 1 (Alkali metals) - elements are very reactive metals
• • Group 7 (Halogens)- reactive non-metals
• • Group 0 (Noble Gases) - non-reactive gases
• The first shell of an atom can only contain 2 electrons
• The other electron shells can only contain 8.
• The electron arrangements written can be found on P6 of the data booklet.
• electon arrangement:

  A) 2 electrons

  B) oxygen

  C) 6 electrons

  D) 2,6

  
• Protons have a positive charge, a mass of 1 amu (atomic mass unit) and are found in the nucleus.
• Electrons have a negative charge, a mass of 0 amu and they spin around the outside of the nucleus.
• Neutrons have a neutral charge, a mass of 1 amu and are found inside the nucleus.
• Atomic number is always the same as the number of protons
• The mass number = atomic number + no. of neutrons
• An isotope is two or more forms of the same element which have the same number of protons but different number of neutrons
• an isotope also has the same atomic number but different mass number.
• nuclide notation:

  A) mass number

  B) atomic number

  C) charge of ion (not in atoms)

  D) element symbol

  
• The relative atomic mass is the average mass of all the atoms of an element in a given sample.
• The relative atomic mass is determined on the percentage of the different isotopes in a sample