Class 2How Atoms combine with similar

and dissimilar atoms• 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 modelReplaced this one

Electron States

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

Note 4s before 3d

Note 4s1 3d5

Note 4s1 3d10

Electron Filling of Orbitals1s 2s 2p 3s 3p 3d 4s 4p 4d Z = 461s 2s 2p 3s 3p 3d 4s 4p 361s 2s 2p 3s 3p 3d 4s 301s 2s 2p 3s 3p 4s 201s 2s 2p 3s 121s 2s 2p 101s 2s 41s 2On Ionisation, 4s levels empties first.

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.

Ionisation energies for the hydrogen atom

4s level just below 3d

Ionic Bonding

Na, z=11, # of electrons and protons, 1s2,2s2,2p6,3s1 : 2+2+6+1=11Note 3s1, lose this electron, full orbitals then ; alkali metalsCl, z=17, 1s2,2s2,2p6,3s2,3p5 : 2+2+6+2+5=17Note 3p5, gain one electron, full 3p6 orbital, halide ionsNa+ ion due to loosing one electron, Cl- due to gaining an electronIonic bonding between elements with different electronegativities.Elements on right of periodic table highly electronegative, and want toGain electrons, elements on left electropositive, lose an electron.Directional so brittle type materials. Ordered structure, move one ionLose order.Crystalline structure from this bonding.

Covalent Bonding

Hydrogen 1s1, Carbon 1s2,2s2,2p2, so if hydrogen can share one electronAnd 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 exhibitCovalent bonds eg carbon.Elements with half full outer orbital.Can be crystalline

Metallic Bonding

Electrons shared in a gas cloud as outer orbitals not filled. Lots of emptyenergy 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.

Ion cores protonsAnd neutrons

Metallic Conductivity

Electrons in Electrons out

Metals are conductive as the electrons are not specific to an ionApplications – electrical wire, copper circuit boards, thermocouples.

Bond Energy and Properties

State25 CSolidSolid

Solids

LiquidSolidSolidSolid

Gases

Bond energy controls melting point.

Primary

Primary

Primary

Secondary

Secondary

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 electronFavors carbon sideWater good example of hydrogen bondBetween hydrogen and oxygen covalentBetween 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?