Atomic structure
Atomic models, Ionisation energies, ionisation trends, electronic structure
- Created by: shanellepaul
- Created on: 29-12-15 13:37
View mindmap
- Atomic structure
- Atomic Models
- Thompson: Plum pudding model - atoms where still a solid sphere but contain -vely charged particles = electrons.
- Dalton: Atoms are solid spheres that made up an element.
- Rutherford: gold foil experiment - firing alpha particles at thin gold foil sheet so alpha particles would be slightly deflected by +ve 'pudding' making up most of the atom.
- Findings: most alpha particles passed through the gold atoms, very few were deflected back.
- Bohr's model: a cloud of electrons would spiral into nucleus and atom would collapse.
- Electrons must exist in fixed shells. Each shell has a fixed energy. Electrons move between shells and EM radiation is emitted or absorbed. energy in shells is fixed so the radiation has a fixed frequency.
- Electronic structure
- Each electron shell has a principal quantum number.
- The further away a shell is from the nucleus the higher its energy level and PQN.
- Not all electrons in the same shell have the same energy.
- Shells are divided into subshells. Different electron shells have different numbers of sub shells.
- Sub shells: S,P,D,F
- S = 1 orbital P = 3 orbitals D = 5 orbitals F= 7 orbitals
- Each orbital holds 2 electrons.
- S = 1 orbital P = 3 orbitals D = 5 orbitals F= 7 orbitals
- Sub shells: S,P,D,F
- Shells are divided into subshells. Different electron shells have different numbers of sub shells.
- 4s subshell has lower energy than 3d subshell.
- Elements in periodic table are classified depending on what letter orbital their outermost electron is in.
- Ionisation energy
- measured for gaseous atoms so use (g)
- Factors affecting IE: Nuclear charge, Distance from nucleus and shielding.
- Nuclear charge: more protons in nucleus = stronger +ve charge and attraction for electrons.
- Distance from nucleus: attraction falls with distance.
- Shielding: as number of electrons between nucleus and outer electrons increases the outer electron is less attracted to the nucleus.
- High IE = high attraction between nucleus and electrons so more energy is needed to remove the electron.
- Ionisation trends
- Al has lower IE than Mg. Al outer electron is in a 3p orbital not 3s.
- 3p is found further away from the nucleus. 3p experiences additional shielding from 3s electrons.
- These two factors override the effect of increased nuclear charge.
- Evidence for theory of electron shells
- These two factors override the effect of increased nuclear charge.
- 3p is found further away from the nucleus. 3p experiences additional shielding from 3s electrons.
- S has a lower IE than P.
- Shielding is identical as being removed from the same orbital - 3p.
- S outer electron experiences repulsion as its in a paired orbital.
- Repulsion between 2 electrons in an orbital makes electrons easier to remove from shared orbitals.
- Evidence for electronic structure model.
- Repulsion between 2 electrons in an orbital makes electrons easier to remove from shared orbitals.
- S outer electron experiences repulsion as its in a paired orbital.
- Shielding is identical as being removed from the same orbital - 3p.
- Al has lower IE than Mg. Al outer electron is in a 3p orbital not 3s.
- Atomic Models
Comments
No comments have yet been made