Module 1 Prpoties of Atoms and Compounds

• Elements are the simplest form of matter and cannot be broken down into simpler substances.
• Atoms structure:

  Particle: Proton Relative Charge: +1Mass (atomic mass): 1

  Particle: Neutron Relative Charge: 0Mass (atomic mass): 1

  Particle: Electron Relative Charge: -1Mass (atomic mass): 1 / 1837

  protons and neutrons are in the nucleous of the atom but electrons are on the outer shells
• Mass number= protons+neutrons

  atomic number= protons=electrons

  neutrons= mass number - atomic number
• Isotopes: atoms of the same elements which have the same protons number, but different nucleon number E.g. Carbon 12 and Carbon 14.

  Two types of Isotopes:

  • non-radioactive isotopes
  • radioactive isotopes which are unstable atoms that break down giving radiations
• Electron shell structure: 2, 8, 8, 18.

  the number of elctrons in shells= 2n^2
• Mixture: two or more elements mixed together but not chemically combined

  Compound: substance in which two or more different elements are chemically combined
• how to write forumals of ionic compounds:

  1. write the elements with their charges at the top
  2. drop their charges and do the the croos method for example ca2 and cl1 would be CaCl2
• Electorn configuration:

  first shell can conatin 2 electrons 2nd shell 8 electrons 3rd shell 18 electrons and so on
• Advanced electron configuration:

  Each shell is split into subshells and each subshelles is made up of a number of orbitals

  They are in the order S,P,D,F
• 1st shell only conatins s subshells, 2nd shells conatins s,p subshells, 3rd shells conatin s,p,d subshells, 4th shells conatin s,p,d,f subshellsThe s subshells only conatins one orbital, the p subshells 3 orbitals, the d subshells, 5 orbitals, the f subshells conatins 7 subshells. An orbital is defined as the region of space surronding an atomic nucles in which one or teo electors move. note that each orbital can conatin a max of 2 electronsThe order in which electrons fill up subshells is:1s,2s,2p,3s,3p,4s,3d,4p,4d,4f
• Ionsaition energy: the energy requried to remove an electron and make an ion. The stronger the attarction between th electron and the postive nuclei, the higher ionsation energy requried to remove the electron. electrons further awy from the nucleus will have a lower ionsation energy than the ones closer to the nucleus.
• Electorn sheielding: the blocking of valence shell electron attraction by the nucleus, due to the presence of inner-shell electrons. electron shielding reduces the ionsation energy. ionsation energy decasres down a group because outer shells are further away from the nucleus hence less attracted to the nuclesus. and increases across a peroid because the outer shells are closer to the nucleus hence more attracted to the nucleus
• electronegativity: the ability of an atom to attract the pair of electrons in a bond. electronegativity increases going across because the electrons are more strongly attracted to the nuclesus. electronegativity decrases going down the group because the electrons are less strongly attracted to the nucleus, because they are more further away
• Atomic radduis: the total distance from the nucleus to the outermost shell of electrons. increases as you move down a group and decasres going across
• Radiostopes


  Unstable nuclei that undergo radioactive decay, emitting particles or energy to become more stable
• Types of radiation


  • Alpha particle
  • Beta particle
  • Gamma ray
• Alpha particle


  • Made up of 2 protons and 2 neutrons
  • Atomic number decreases by 2
  • Atomic mass decreases by 4
  • Can only travel a few cm in the air
  • Stopped by a sheet of paper
• Beta particle


  • Electron particle that gets ejected from the nucleus when a neutron decays into a proton
  • Can travel a few m in the air
  • Can pass through a sheet of paper
  • Stopped by a thin sheet of metal
• Gamma ray


  • Super high energy electromagnetic radiation
  • High frequency
  • Small wavelength
  • Can travel km in the air
  • Can even go to space
  • Stopped by a few cm of lead or meters of concrete
• particle equations reprsents when radioactive isotopes undergo radioactive decay.
• Half life: The average time taken for the number of nuclei in a sample to halve. for example, if there are 7200 carbon 11 atoms at one time and then 3600 atoms left after 20 minutes, the half life is 20 minutes.
• Bond polarity: the unequal sharing of electrons between atoms in a bond, which results in a speration of charge across the bond. we consider the bond to be plar colavent if the differnce in electronegativity values is gretaer than 0 and ionic if its greater than 1.7
• the polarity of diatomic molecules is depand on the polarity of the bond. a greater electronegativity results in a bond being more polar.

  The polarity of polyatomic depend on both shape and polarity. symmetrical bonds mean that all arrows condruct eachother. Symmetrical molecules are non polar and assymetrical molecules are polar
• Shapes of molecules:

  linear: number of bonding pairs of electrons =2, number of lone pairs=0,180 deggres

  Triogal planar: 3 bonding electron pairs and 0 lone pairs,120 deggres

  bent: 2 pairs of bonding elctrons, 1 lone pair

  tetrahedral: 4 bonding pairs of electrons, 0 lone pair

  Trigonal pyramidal: 3 bonding elctron pairs, 1 lone pair
• Ions from when atoms lose or gain elctrons, to gain a full outershell.

  • Anion are negative
  • cations are postive
• Ionic bonding:

  • An electrostatic force of attraction between oppistoely charged ions
  • occurs between metals and non metals
  • they are strong
  • form gaint ionic lattices
• covalent bonding:

  • formed by the sharing of outershell electrons to allow the formation of a full outershell
  • genertaes an electrostatic force of attratction between the postivley charge nuceli and the electrons
  • occurs between two non metals
• Types of covalent bond:

  • single covalent bond: sharing of 1 pair of electrons
  • Multiple covalent bond: sharing of more than one elctron pair
  • Coordiante covalent bond: both bonding electrons are contriubted from the same atom