chap 3 - atomic structure

• all matter is made up of atom
• atom is the smallest indivisible <cannot be divided> unit of matter
• inside an atom, there are 3 subatomic particles

  • protons
  • neutron
  • electron

  where protons and neutron is found in the nucleus and the electron is found in the electron shell
• proton and neutrons are found in the nucleus <centre of an atom>
• electron is found in the electron shells <electrons revolves around the nucleus in the electron shell>
• • proton

  symbol= p

  relative mass= 1

  relative charge= +1
• • electron

  symbol= e-

  relative mass= 1/1836 <0>

  relative charge= -1
• • neutron

  symbol = n

  relative mass= 1

  relative charge= 0
• mass of atom = sum of masses of all sub-atomic particles in an atom
• mass of atom= mass of proton + mass of neutron
• an atom is electrically neutral <no overall charge> because the no. of positive charges(protons) = no. of negative charges(electrons)
• nucleons number(mass no.) is the sum of no. of protons and neutrons in an atom
• protons no. (atomic no.) is no. of protons in an atom
• proton no. is unique to each element <no. of protons is different for each element>
• outermost electron shell of an atom is valence shell
• electrons found in valence shell is valence electrons
• isotopes are atoms that have the same no. of protons but different no. of neutrons
• isotopes have similar chemicals properties slightly different physical properties
• isotopes have identical chemical properties because they have the same no. of valence electrons
• isotopes have slightly different physical properties because they have different masses <diff nucleon no.> which affects physical properties
• atomic no. is the no. of protons in an atom
• mass no. is the sum of no. of protons and no. of neutrons in an atom
• mass no. of isotope formula

  --> mass no. = no. of protons + no. of neutrons
• two atoms are isotopes if they have the same no. of protons but different no. of neutrons
• no. of protons = no. of electrons --> atom

  no. of protons <not equal> to no. of electrons --> ion