Electron Configuration and Lewis Dot Diagrams We have seen that LDD’s represent the valence electrons only. Here we see Fluorine is represented by the symbol F surrounded by the 7 valence electrons. (10 sec) Both of these mean the same thing

F Lewis Dot Diagram Element symbol represents: Dots represent: Nucleus AND All inner core electrons Dots represent: Valence electrons (outer shell – Highest occupied energy level) F So make sure your notes have these key points (15 sec)

Stable Electron Configurations – Lewis Dot Diagrams Assigning valence electrons across the period table is simple group

Stable Electron Configurations – Lewis Dot Diagrams

Stable Electron Configurations – Lewis Dot Diagrams

Stable Electron Configurations – Lewis Dot Diagrams

Stable Electron Configurations – Lewis Dot Diagrams

Stable Electron Configurations – Lewis Dot Diagrams

Stable Electron Configurations – Lewis Dot Diagrams

Stable Electron Configurations – Lewis Dot Diagrams

Stable Electron Configurations – Lewis Dot Diagrams

Formation of Ions When an atom gains or loses an electron(s)  atom is no longer neutral. # of Protons NO LONGER EQUAL # of electrons Definition: ION = atom (or group of atoms) with positive (+) or negative (-) net electric charge.

Formation of Ions ANION = Ion with a negative (-) charge [Memory aid: anion = A Negative ION] Example: Chlorine atomic # 17 Halogen Family/Group 7A 7 Valence Electrons Neutral (but not stable) - 17 protons and 17 electrons To become stable – gain 1 electron in outer e- shell Now have 1 more e- than proton = -1 net charge Symbol is written Cl- or Cl1-

Formation of Ions CATION = Ion with a positive charge Example: Sodium atomic # 11 Alkali Metal Family/Group 1A 1 Valence Electron Neutral (but not stable) -11 protons and 11 electrons To become stable – lose the 1 electron in outer e- shell Now has 1 more proton than electron = 1+ net charge Symbol is written Na+ or Na1+

Bonding MNM MM NMNM Elements achieve stable electron configurations by transferring or sharing electrons between atoms Transferring Electrons - Those with <4 valence electrons “LEND” them These elements “lose” valence electrons OR Those with >4 valence electrons “BORROW” them These elements “gain” electrons

Formation of Ions & Bonding Sodium reacts with chlorine  electron transferred from sodium to chlorine Each atom ends up more stable

Formation of Ions & Bonding Sodium reacts with chlorine  electron transferred from sodium to chlorine Each atom ends up more stable

Formation of Ions & Bonding

LDD’s for Ions - + Na Cl

Ionic Bonding Chemical bond Opposites attract Ionic bond Chemical bond = force that holds atoms or ions together as a unit. Opposites attract Particle(s) with negative charge attracts particle(s) with positive charge. Ionic bond Force that holds cations and anions together and which involves the transfer of electrons. Bond occurs between a metal and a nonmetal

Mg2+ , Cl- Ionic Bonding Ions Lewis Dot Ionic Compounds What is the chemical formula for magnesium chloride? Mg and Cl First determine the Lewis Dot Diagram and Ions for each element:

Ionic Bonding Mg + 2Cl OR Mg atom cannot reach a stable electron configuration by giving up just 1 valence electron or reacting with just 1 chlorine atom.

Ionic Bonding Mg transfers 2 electrons, one to each of the 2 Cl atoms. After transfer  Charge on the magnesium ion is 2+ Charge on the 2 chloride ions is 1-

- - Ionic Bonding 2+ Formula for magnesium chloride is MgCl2 When it’s ionic the electrons are completely donated so they should not be drawn as shared electrons

Covalent Bonding Non –metal with Non-metal Eg CH4 Covalent compounds have real bonds shared electrons so the LDD should have shared electrons and they may not be shared equally but must be represented as shared