Unit 5 Chemical Bonding
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Transcript of Unit 5 Chemical Bonding
UNIT 5 CHEMICAL BONDINGChapter 6.1 Lewis Dot Diagrams & Ions
STABLE ELECTRON CONFIGURATIONS
When is an atom unlikely to react?When the outer shell (highest occupied
energy level) is filled with electrons 8 e- for Octet Rule
Noble gases are the most stable elements.The highest occupied energy level is
completely filled. Elements tend to react to achieve
electron configurations similar to those of noble gases.
STABLE ELECTRON CONFIGURATIONS
Chemical properties of an element depend on the number of valence electrons.
Electron dot diagram - [Lewis Dot Model] is alternative to standard electron shell diagramDot diagram emphasizes valence
electrons (inner shells hidden)
ELECTRON CONFIGURATION AND LEWIS DOT DIAGRAMS
F F
Lewis Dot Diagram
Both of these mean the same thing
LEWIS DOT DIAGRAM
Element symbol represents:Nucleus
ANDAll inner core electrons
Dots represent: Valence electrons (outer shell –
Highest occupied energy level)
F
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
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 # 17Halogen Family/Group 7A
7 Valence ElectronsNeutral (but not stable) - 17 protons and 17
electronsTo 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
Naming Anions:Part of element name + suffix “ide”
Example: Chlorine ion becomes “chlor” + “ide”
Cl- is called a chloride ion F- is the fluoride ion (“fluor” + “ide”) Br- is the bromide ion (“brom” + “ide”) I- is the iodide ion (“iod” + “”ide”)
FORMATION OF IONS
CATION = Ion with a positive charge Example: Sodium
atomic # 11Alkali Metal Family/Group 1A
1 Valence Electron Neutral (but not stable) -11 protons and 11 electronsTo 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+
FORMATION OF IONS
Naming Cations:Use the normal element name
Na+ is called a sodium ion Li+ is the lithium ionCs+ is the cesium ionFr+ is the francium ion
BONDING
Elements achieve stable electron configurations by transferring or sharing electrons between atoms
Transferring Electrons -Those with <4 valence electrons “LEND”
themThese elements “lose” valence electrons
OR
Those with >4 valence electrons “BORROW” themThese 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
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
IONIC BONDING
Chemical bond = force that holds atoms or ions together as a unit.
Opposites attractParticle(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
IONIC BONDING
Ionic Compounds What is the chemical formula for magnesium
chloride? Mg and Cl
First determine the Lewis Dot Diagram and Ions for each element:
Mg2+ , Cl-Ions Lewis Dot
IONIC BONDING
Mg atom cannot reach a stable electron configuration by giving up just 1 valence electron or reacting with just 1 chlorine atom.
Mg + 2Cl OR
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
Formula for magnesium chloride is MgCl2
2+ --
PROPERTIES OF IONIC COMPOUNDS
The properties of sodium chloride are typical of ionic compounds.High melting point
sodium chloride melts ~800°CWhen solid - poor conductor of
electric currentWhen liquid (melted) - good conductor
of electric current. Brittle - crystals shatter when struck
with a mallet
EXIT SLIP
Draw the Lewis Dot Diagrams for the Nitrogen Family.
Provide and name the ions for Oxygen, Calcium, and Sulfur.
What is the chemical formula for Aluminum Fluoride? Show the steps you used to determine the
formula.