5.1 Electron structure

• Electrons are in constant motion around the nucleus of the atom
• Electrons are found in energy levels or shells
• Shells are made up of sub-shells
• Sub-shells are made from orbitals
• An atomic orbital is a region around the nucleus that can hold up to two electrons in opposite spins
• S orbital can hold up to two electrons and is spherical shaped
• P orbital can hold up to six electrons, has three lobes and is dumbbell shaped
• D orbital can hold up to ten electrons, has four lobes and is football shaped
• Electrons fill orbitals in order of increasing energy
• Sub-shell 4s is filled before 3d
• Orbitals are filled by single electrons before pairing
• S-block elements have their highest energy electrons in the s sub-shell
• p-block elements have their highest energy electrons in the p sub-shell
• d-block elements have their highest energy electrons in the d sub-shell