1. The Energiser…….. Se 11 Na 1. How many protons does this element have?23 Na
2. How many electrons does this have? Se 34 79
3. Write out the electronic structure of Mg. 24 12
4. How does reactivity change down group 1?

2. The Energiser……..
5. How does the electronic structure of Na compare to that of Mg?
6. How does the electronic structure of N compare to that of P?
7. What is common about the following: Na, Mg, Zr, Al, Bi, W?
8. What charge does Ca commonly carry as an ion?
9. How many outershell electrons do elements in group 5 have?

3. The Energiser……..
10. Name the scientist who’s nuclear model of the atom forms the basis of current ideas on atomic structure?
Bonus! What was the plum pudding theory and why was it disproved?

4. Evidence for atomic structure
L.O. To understand what is meant by ionisation energy.
To be able to describe electronic structure using data on successive ionisation energies.
How do we know how electrons are arranged?

5. Geiger-Marsden’s Experiment :
Alpha particles, [ He2+ ] were fired at a thin gold foil
Most pass through unaffected
Few pass through but deflected
VERY few reflected back towards source
Suggests that:
mass (protons + neutrons) and positive charge (protons) of atom concentrated in VERY small part of atom
ie the NUCLEUS
and most of the atom’s volume is empty space containing the electrons
ie the ENERGY LEVELS

6. N.B: Always ENDOTHERMIC (you can tell by the sign!)
What do you know about ionisation and ionisation energy?
FIRST IONISATION ENERGY (Em1) of an atom: the energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form gaseous 1+ ions.
M(g) M+(g) + e (kJ mol-1)
N.B: Always ENDOTHERMIC (you can tell by the sign!)
Successive energies for an element get larger

7. Can you describe AND explain the graph below?Na X

8. Successive ionisation energies for Sodium
Data suggest ONE electron most EASILY removed (furthest from, and most shielded from nucleus).
 one electron in outer energy level
 Na belongs to group 1 of periodic table
“similar” Em values correspond to electrons being removed from same electron shell.
Inner 2 electrons hardest to remove. They have no shielding from the nucleus.
Na belongs to period 3 because 11 e- divided into 3 energy levels
Test yourself p53

9. How do we explain ionisation energies of successive elements?He Ne Ar Li Na K

10. Subshells Level 4 – 4 orbitals – 4s, 4p, 4d, 4f
Each main energy (principal quantum) level is split into sub levels.
The sub levels are called ORBITALS.
Principal Quantum Level 1
Principal Quantum Level 2
Principal Quantum Level 3
 1 orbital 1s
 2 orbitals
2s 2p
 3 orbitals
3s 3p 3d
Level 4 – 4 orbitals – 4s, 4p, 4d, 4f
For now, concentrate on understanding orbital filling up to 4p!
Test yourself p

11. True or False False Na – 11 protons Electron structure 1s2 2s2 3s1 2p6
S – 16 protons Electron structure 1s2 2s2 2p6 3s2 3p5
True
Ar – 18 protons Electron structure 1s2 2s2 2p6 3s2 3p6
False
Be – 4 protons Electron structure 1s2 2s1 2p1
True
O – 8 protons Electron structure 1s2 2s2 2p4