1. Class 2 How Atoms combine with similar and dissimilar atoms
Periodic table
Electron configurations
Energies
Bond types
Bond types and properties.
Fall 08

2. Columns represent groups of similar properties, Group 1A, alkali metals; 8, inert gases; 7B halides

3. Atomic Model Nucleus – Protons +ve charge Neutrons no charge
Orbitals – Electrons –ve charge
Atoms – protons and electrons
balance each other, so
no net charge.
Ions – Positive or negative
charge imbalance
Na+ or Cl-
Quantum mechanical model
Replaced this one

4. Electron States Each Quantum Number Fills up first- 1, 2, 3,4,5,6 etc
Chlorine atom, z=17, 1s2,2s2,2p6,3s2,3p5, electrons = =17
So 1S2,then 2S2,2p6, then 3S2,3P6,3D10,then 4S etc – there are some
Discrepancies though.

5. Note 4s before 3d
Note 4s1 3d5
Note 4s1 3d10

6. Electron Filling of Orbitals
1s 2s 2p 3s 3p 3d 4s 4p 4d Z = 46
1s 2s 2p 3s 3p 3d 4s 4p 36
1s 2s 2p 3s 3p 3d 4s 30
1s 2s 2p 3s 3p 4s 20
1s 2s 2p 3s
1s 2s 2p
1s 2s 1s
On Ionisation, 4s levels empties first.

7. Filling of Shells
Electrons shells like to be full, half full or empty.
Full shells – inert status, for example helium
Full or empty, between elements by ionic
or covalent bonding.
Metallic bonding – sharing of electrons.

8. Periodic Table Rows – number of shells 1,2,3,4 etc
Column – number of electrons in outer shell
Columns have like properties as number of electrons in outer shell same.
Atomic number – number of electrons and so protons in atom.
Different number of electrons changes properties and produces elements

9. Bonding Types Between like atoms – metallic or covalent
Between different atoms – metallic, ionic or covalent.
Primary – ionic, covalent and metallic.
strong
Secondary – hydrogen, van der Waals.
weak.

10. Ionisation energies for the hydrogen atom
4s level just below 3d
Ionisation energies for the hydrogen atom

11. Ionic Bonding
Na, z=11, # of electrons and protons, 1s2,2s2,2p6,3s1 : =11
Note 3s1, lose this electron, full orbitals then ; alkali metals
Cl, z=17, 1s2,2s2,2p6,3s2,3p5 : =17
Note 3p5, gain one electron, full 3p6 orbital, halide ions
Na+ ion due to loosing one electron, Cl- due to gaining an electron
Ionic bonding between elements with different electronegativities.
Elements on right of periodic table highly electronegative, and want to
Gain electrons, elements on left electropositive, lose an electron.
Directional so brittle type materials. Ordered structure, move one ion
Lose order.Crystalline structure from this bonding.

12. Covalent Bonding
Hydrogen 1s1, Carbon 1s2,2s2,2p2, so if hydrogen can share one electron
And carbon can share four electrons, both elements will have full orbitals.
Four hydrogens share with one carbon in covalent bonds.
Molecule of methane gas formed – different elements or same can exhibit
Covalent bonds eg carbon.Elements with half full outer orbital.Can be crystalline

13. Metallic Bonding Ion cores protons And neutrons
Electrons shared in a gas cloud as outer orbitals not filled. Lots of empty
energy states, such as 3d etc. Can be single element, eg gold, or mixtures
such as brass, or aluminum alloys. No directionality to bonds, so ductile
and conductive. Crystalline usually, but not ordered.

14. Metallic Conductivity
Electrons in
Electrons out
Metals are conductive as the electrons are not specific to an ion
Applications – electrical wire, copper circuit boards, thermocouples.

15. Bond Energy and Properties
State
25 C
Solid
Solids
Liquid
Gases
Primary
Primary
Primary
Secondary
Secondary
Bond energy controls melting point.

16. Secondary Bonding Hydrogen – needs presence of hydrogen,
single electron effect,
non crystalline normally
Van Der Waals – dipole type bonding, due
to slight charge imbalance with distance.
Non crystalline normally.

17. Secondary Bonding Positive charge here as electron Favors carbon side
Water good example of hydrogen bond
Between hydrogen and oxygen covalent
Between molecules, hydrogen bond.

18. Homework How does calcium and flourine bond to each other?
How does aluminum bond to other aluminum atoms and how does silicon bond to other silicon atoms?
Why are metals conductive?