Electron structure

• The principal quantum number indicates the shell occupied by the electrons

  
• A shell is a group of orbitals with the same principal quantum number
• The 1st shell can hold 2 electrons
• The 2nd shell can hold 8 electrons
• The 3rd shell can hold 18 electrons
• The 4th shell can hold 32 electrons
• An orbital is a region around the nucleus that can hold up to two electrons with opposite spins
• An orbital can hold 2 electrons
• The 4 types of orbitals are:

  • s orbital
  • p orbital
  • d orbital
  • f orbital
• The shape of an s-orbital is spherical
• The shape of a p-orbital is dumb-bell shape
• In an S subshell, there is 1 orbital
• In a S subshell, 2 electrons can be held
• In a P subshell, there are 3 orbitals
• In a P subshell, 6 electrons can be held
• In a D subshell, there are 5 orbitals
• How many orbitals are present in a D subshell? 5
• How many electrons can be held in a D subshell? 10
• How many electrons can fill F subshell? 14
• When using ‘electrons in box’ representation, what shape is used to represent the electrons? Arrows
• What letter is used to represent the shell number? n
• From which shell onwards is S orbital present? n = 1
• From which shell onwards is P orbital present? n = 2
• From which shell onwards is D orbital present? n = 3
• From which shell onwards is F orbital present? n = 4
• What are the rules by which electrons are arranged in a shell?

  • Electrons are added one at a time
  • Lowest available energy level is filled first
  • Each energy level must be filled before the next one can fill
  • Each orbital is filled singly before pairing
  • 4s is filled before 3d
• Why does 4s orbital fill before 3d orbital? 4s orbital has a lower energy than 3d before it is filled
• What is the electron configuration of krypton? 1s22s22p63s23p64s23d104p6
• Which electrons are lost when an atom becomes a positive ion? Electrons in the highest energy levels