C2.2.1

• The shell or energy level number is called the principal quantum number ( n )
• The maximum number of electrons in each shell is 2n^2 with n being the principal quantum number or energy level
• what is the maximum number of electrons in the 1st energy level?

  2
• what is the maximum number of electrons in the 2nd energy level?

  8
• what is the maximum number of electrons in the 3rd energy level?

  18
• what is the maximum number of electrons in the 4th energy level?

  32
• Define an orbital

  A region around the nucleus that can hold up to 2 electrons with opposite spins
• Name the different orbitals:

  • s
  • p
  • d
  • f
• S-orbitals:

  • are spherical shaped electron clouds
  • Each energy level contains 1 s-orbital
  • the greater the n number the greater the radius of the s-orbital
  • There is 1 orbital in each s sub-shell
  • 2 electrons can fill an S sub-shell
• Define a sub-shell

  a group of the same type of orbitals within an energy level ( eg 2s 3d )
• P-orbitals:

  • dumb bell shaped electron cloud
  • each energy level after n = 2 contains three p-orbitals ( px , py and pz ) at right angles to one another
  • the greater the principal quantum number (n) the further the p-orbital is from the nucleus
  • there are 3 orbitals in each p sub-shell
  • 6 electrons can fill a p sub-shell
• D-orbitals:

  • each energy level after n = 3 contains 5 d-orbitals
  • 5 orbitals are in each d sub-shell
  • 10 electrons can fill a d sub-shell
• F-orbitals:

  • each energy level after n = 4 contains 7 f-orbitals
  • 7 orbitals are in each f sub-shell
  • 14 electrons can fill an f sub-shell
• Orbitals fill in order of increasing energy
• What does a represent?

  • Each arrow represents an electron ( 2 in each orbital )
  • The arrows are in opposite directions representing the electrons opposite spins

  
• What does b represent?

  • the shape of orbit or orbital type ( s , p , d , f )

  
• What does c represent?

  • the energy level

  
• What is significant about d?

  • the 4s orbital is lower in energy than the 3d orbital and so fills up first

  
• Orbitals with the same energy (in the same subshell ) are occupied singly first
• • electrons are negatively charged and therefore repel each other
  • electrons in the same orbital must have opposite spins
  • this is to counteract the repulsion between the negative charges of the two electrons
• Occupying the same energy subshells singly first prevents any repulsion between paired electrons until there is no further orbital available
• Electron configurations show how subshells are occupied by electrons in an atom.
• The subshell below is filled with 6 electrons, using an and b describe the occupation pattern?


  a , a , b , b

  
• What is a ?

  the principal quantum number ( n )

  
• What is b?

  the subshell

  
• What is c?

  the number of electrons in the subshell

  
• What is d?

  The electronic Configuration of Bromine

  
• Electron configurations can be shortened to nobel gas configurations
• What goes in the bracket in Bromines electronic configuration?

  Ar

  
• What is depicted in the picture?

  the Nobel gas configuration of bromine

  
• Electron configurations can also help to locate elements on the periodic table
• Where is sodium located on the periodic table?

  3 down , 1 across in the s block

  
• What is a?

  the s block

  
• What is b?

  the d block

  
• What is c?

  the p block

  
• What is d?

  the f block

  
• What does a represent?

  Rows down

  
• What does b represent?

  the block

  
• What does c represent?

  columns across

  
• Why is sodium in the s block?

  sodium is in the s block because its highest energy electron is in the s subshell