Bonding Between Atoms

Bonding Between Atoms Why do atoms form bonds? To get a stable octet of valence electrons. Called a “noble gas configuration”

Two Major Types of Bonds IONIC BOND Metal and Nonmetal valence e- transferred COVALENT BOND All nonmetals valence e- shared Crash Course: https://www.youtube.com/watch?v=QXT4OVM4vXI

Changes in Energy Energy is released when bonds form. exothermic Lower energy = more stable Exothermic = Bond Forms Endothermic = Bond Breaks

Lewis Dot Diagrams of Atoms Show valence electrons involved in bonding

Lewis Dot Diagrams of Ions Positive Ions (cations): lose outer shell valence to get stable octet. Negative Ions (anions): gain electrons to complete outer shell octet. What are Ions (4:44) https://www.youtube.com/watch?v=900dXBWgx3Y

Ionic Bonding Happens between metals and nonmetals What are Ionic Bonds? (1:30) https://www.youtube.com/watch?v=zpaHPXVR8WU

Atoms Become Ions Metals Lose Electrons: Ex: Mg is 2-8-2 Loses 2 electrons to become Mg+2 2-8 Nonmetals Gain Electrons: usually take top (-) charge become (–) ion Ex: Cl is 2-8-7 Gains 1 electron to become Cl-1 2-8-8

Ionic Bond = Electron Transfer As ions form, an exchange or transfer of electrons happens. Lithium (metal) 2-1 Fluorine (nonmetal) 2-7

They transfer enough electrons so that all get a stable octet of valence! Na before: 2-8-1 Na after: 2-8 Cl before: 2-8-7 Cl after: 2-8-8 Mg before: 2-8-2 Mg after: 2-8 O before: 2-6 O after: 2-8 Ca before 2-8-8-2 Ca after 2-8-8 Cl before: 2-8-7 Cl after: 2-8-8 (Happens twice!)

Electronegativity Difference Ionic compounds: large differences in atomic EN values ( > 1.7) Greater EN diff. = more “Ionic Character”.

Ex: EN Values Metal Na = 0.9 Nonmetal Cl = 3.2 Nonmetal with higher EN “takes” electron(s) from metal

Positively and negatively charged ions form and attract each other due to OPPOSITE CHARGES. IONIC BOND Forming Table Salt :6 minutes http://science360.gov/obj/video/c8b6ed58-5791-4fc1-8619-62fd8d99d9d0/atoms-bond-ionic-bonds - ion + ion

Ionic compounds have uniform crystalline lattice structure. https://www.youtube.com/watch?v=lhC42qxk5kQ&safe=active

Can you identify an ionic compound from a covalent? _____________MgBr2 _____________Ca(NO3)2 _____________P2O5 _____________CO2 _____________Na2S _____________H20

Drawing Lewis Dot Diagrams of Ionic Compounds Page 7 Bonding Packet

Ionic Compounds are Neutral “Subscripts” show ratio of ions Total positive and negative charges must balance so the compound is electrically neutral.

Writing Neutral Ionic Formulas Write symbols of elements Write the charges Criss-Cross charges if necessary to balance the formula Put parenthesis around polyatomic ions if more than one in formula Simplify if needed. Tutorial on writing ionic formulas 9 min http://www.youtube.com/watch?v=vscoYh6m46M

Stock System for Naming Ionic Compounds Binary: Contain ions of 2 elements Ex: MgCl2, Al2O3, NaCl

Name nonmetal with “-ide” ending. Naming Binary Ionics Name metal Name nonmetal with “-ide” ending. Note: Name never indicates # of ions Ex: NaCl, MgBr2, CaO, Al2S3 Writing Ionic Formulas: (3:22) https://www.youtube.com/watch?v=vfYnhnfdsD0

Ternary Ionics: Contain 3 elements Polyatomic ion present. Note: Elements inside the polyatomic ion are covalently bonded (all nonmetals). These compounds contain both ionic and covalent bonds!! MgSO4

Naming Ternary Ionics (with polyatomic) Name Metal Name polyatomic ion If two polyatomics, name them both Ex: NaNO3, Ca3(PO4)2, NH4Cl Ionics with Polyatomic Ions: (3:46) https://www.youtube.com/watch?v=JylJwHryeSU

Why does the 3rd compound use a Roman Numeral in it’s name?

When to Use a Roman Numeral Roman numerals are used when the metal can have more than one possible charge. Roman numeral indicates the charge the metal takes in that compound and must be indicated in the name Ex: NiBr2 Nickel II Bromide NiBr3 Nickel III Bromide

Name the following ionic compounds: Fe(NO3)3 ____________________ NaF _________________________ Cu3P ________________________ Al2(SO4)3 ____________________

Write the correct formula for: _____________cobalt III oxide _____________magnesium sulfide _____________ lead II nitrate _____________ calcium phosphate

Properties of Ionic Compounds

High Melting Point Attraction between ions is very strong. Requires large amount of heat energy to separate ions and make solid melt. Higher MP than covalents

Solubility in Water Most ionics will dissolve in water, or be “soluble”. When dissolved in water they are “aqueous” Ex: NaCl (aq)

Water is a “polar molecule”. Acts like magnet to pull ions apart and into solution. Ions are now “dissociated” or “hydrated” ions. http://youtu.be/EBfGcTAJF4o

Conductivity Ionic compounds conduct when ions are “mobile” or free to move about. Ionic compounds conduct when: Molten (melted or liquid) (l) Aqueous (aq)

Molten Ionics can Conduct!

Conductivity DO NOT conduct when solid as the ions locked in place. Most covalents do not conduct

Which compound has the highest Melting point? KCl or SO2 Which substances conduct electricity? NaCl (s) CO2 (g) MgBr2 (l) C6H12O6 (s) LiNO3 (aq)

Dancing Queen: Song about Ionic vs Covalent Bonding Crash Course Chemistry: Nomenclature (only watch first 6 minutes, skip section on naming acids for now) http://www.youtube.com/watch?v=mlRhLicNo8Q Dancing Queen: Song about Ionic vs Covalent Bonding http://www.youtube.com/watch?v=QIfTT-_-xLo Crash Course: Atomic Hookups http://www.youtube.com/watch?v=QXT4OVM4vXI