Class 2
How Atoms combine with similar
and dissimilar atoms
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Periodic table
Electron configurations
Energies
Bond types
Bond types and properties.
Fall 12
Columns represent groups of similar properties, Group 1A, alkali metals; 8, inert gases; 7B halides
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
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 = 2+2+6+2+5=17
2
So 1S2,then 2S ,2p6, then 3S2,3P6,3D10,then 4S etc – there are some
Discrepancies though.
Note 4s before 3d
Note 4s1 3d5
Note 4s1 3d10
Electron Filling of Orbitals
1s 2s 2p 3s 3p 3d 4s 4p 4d
Z=
1s 2s 2p 3s 3p 3d 4s 4p
1s 2s 2p 3s 3p 3d 4s
1s 2s 2p 3s 3p 4s
1s 2s 2p 3s
1s 2s 2p
1s 2s
1s
On Ionisation, 4s levels empties first.
46
36
30
20
12
10
4
2
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.
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
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.
4s level just below 3d
Ionisation energies for the hydrogen atom
Ionic Bonding
Na, z=11, # of electrons and protons, 1s2,2s2,2p6,3s1 : 2+2+6+1=11
Note 3s1, lose this electron, full orbitals then ; alkali metals
Cl, z=17, 1s2,2s2,2p6,3s2,3p5 : 2+2+6+2+5=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.
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
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.
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.
Bond Energy and Properties
State
25 C
Solid
Solid
Primary
Solids
Primary
Liquid
Solid
Solid
Solid
Primary
Gases
Secondary
Secondary
Bond energy controls melting point.
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.
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.
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?