Atom structure, periodic table, chemical formulas

• Dalton-marbles (1803)

  Thompson - plum pudding (1897)

  Rutherford- nucleus and outer part (1911)

  Bohr- planetary model (1913)
• There are 3 subatomic particles; electron, proton and neutron
• The atomic mass unit(amu) can be defined as the mass of single proton.

  A neutron has a mass of 1amu

  An electron has a mass of 1/1840amu
• The protons and neutrons are found in the nucleus of the atom
• The electron orbit the nucleus of the atom

  The electron cloud is the area in which the electrons move around and orbit the nucleus
• The atomic number is the number if protons in the nucleus.
• The mass number is the number of protons & neutrons in the nucleus
• No. Of neutrons= mass no. - atomic no.
• No. Of electrons= no. Of protons
• Nucleus= no. of protons = atomic number

  No. Of neutrons= mass no. - atomic number
• Electron orbits= no. of electrons=no. of protons
• The nucleus formula of an element shows its mass & atomic number, alongside the symbol e.g ²⁷Al

  ¹⁹
• The electron configuration of an element is a simple list of the number of electrons in each orbit of the atom e.g Ca- 2,8,8,2
• The number of protons determines the type of atom/element present.
• The number of electrons determines how it reacts
• The number of neutrons can vary
• Isotopes are atoms with the same atomic number but with different mass numbers
• The periodic table is an arrangement of elements in order of increasing atomic number.
• Each row of the table is called a period, it shows the number of electron shells present in the atom.
• Each column of the table is called a group, it shows the number of electrons in the outer shell of the atom
• Metals:

  • Left
  • Fe,Zn,Na,Cu
  • Shiny, metallic lustre
  • Flexible solids
  • Conduct electricity
  • Tend to lose electricity
• Non-Metals

  • Right
  • C,S,O,F
  • Dull, no lustre
  • Brittle solids, liquids, gases
  • Do not conduct electricity
  • Tend to gain/share electricity
• An atom with a full outer shell is unreactive, if the outer shell isn't full the atom will react
• Octet rule states that when bonding occurs atoms will lose, gain or share electrons until they get a full outer shell(8)
• A chemical bond occurs between 2 atoms when these atoms lose, gain or share electrons
• A molecule is a group of atoms bonded together
• Ionic bonding occurs between a metal ion and a non-metal ion
• An ion is a charged atom
• Metals form positive ions
• An ionic bond is the force of attraction between 2 oppositely charged ions
• Characteristics of ionic substances

  1. Form solid at room temperature, have high MP & high BP
  2. Dissolve in H2O not in hexane
  3. Conduct electricity when molten or dissolved
• Radicals

  Are groups of bonded atoms that carry a charge emg SO4²-, OH-
• Covelant bonding occurs when non-metals bond together
• A covelant bonds occurs when 2 atoms share a pair of electrons

  Double covelant bond forms when 2 atoms share 2 electrons
• Characteristics of covelant bonding

  • Form liquids and gases at RT, have low MP & BP
  • Do not dissolve in H2O, do in hexane
  • Do not conduct electricity when molten or dissolved
• Valency of an atom is the number of electrons lost, gained or shared during bonding
• Valency | example

  1 | group 1, gp 7- OH-

  2 | gp 2 , gp 6 - CO3²-

  3 | gp 3, gp 5

  4 |gp 4
• Example:

  Li O

  Val: 1 2

  +1 

  = =

  2 2