Presentation on theme: "How many valence electrons do atoms want to obtain?"— Presentation transcript:
How many valence electrons do atoms want to obtain?
A bond is the electrostatic force of attraction between two particles (atoms, ions or molecules)
They are formed/broken during Chemical Reactions Formed = release energy Broken = absorb energy
Valence Electrons - want to achieve happiness “Octet Rule” - want a full valence shell = HAPPY!
Ionic Covalent Metallic - metal and nonmetal - nonmetal + nonmetal - metal + metal Atoms Involved
Find the correct formula for a compound!! Use the oxidation #’s Put the positive one first H +1 + O -2 H 2 O
Ca + Br CaBr Mg + (OH) Mg(OH) Sr + O Sr 2 O SrO
Na + Se Na 2 Se Fe (III) + (HCO 3 ) Fe(HCO 3 ) Al + PO 4 Al 3 (PO 4 ) Al(PO 4 )
Remember: A bond between a metal and a non-metal atom The metal keeps its name, and the non-metal ends in -ide KBr CaCl 2 Potassium Bromide Calcium Chloride
Wings – Bonding Video
What are the formulas for the compounds between: Oxygen and Phosphorus Iodine and Barium
HON – 17 As pure elements, these seven elements form molecules containing two atoms 3 H2H2 N2N2 O2O2 F2F2 Cl 2 Br 2 I2I2
HON – 17 As pure elements, these seven elements form molecules containing two atoms 3 Transition Elements
Atoms combine to form compounds their properties change By bonding atoms together, their properties change I. Bonding A.Chemical Bond This is the attractive force between atoms or ions Results from the rearrangement of valence electrons B. Energy Changes As a chemical bond forms, atoms are brought to a lower energy state Free atoms have more energy than bonded atoms H2H2 O2O2 H2OH2O
Energy Potential Energy HH Free atoms Bonded atoms HHHHHH H2H2 HHHHHHHH H2H2 Making Bonds Breaking Bonds Exothermic Endothermic Chemical Energy Energy released as a bond is formed Energy used to break chemical bonds Energy Chemical energy is considered potential (stored) energy.
C. Stability Two atoms drop to lower energy states when they bond. They are now more stable More energy released during bond formation, more stable the bond More energy released during bond formationStronger Bond Need more energy to break these bonds apart energy To break it, add little energy Weak Bond energy Releases lots of energy energy Strong Bond Releases little energy. To break it, add lots of energy
As we said before, atoms can bond together by moving their valence electrons around Actually, atoms can either lose, gain or share electrons. This gives us several types of bonds Ionic BondAtoms transfer electrons Creates ions Forming ionsAn ion is formed when atoms lose or gain electrons Ion =Charged atom due to a loss or gain of electrons e- e-e- -+
Binary Ionic Compounds - change the end of the non-metal to -ide MgI 2 Magnesium Iodide CoBr 2 K 2 O CoBr 3 Potassium Oxide Cobalt (II) Bromide Cobalt (III) Bromide
When you have more than two elements, refer to Ref. Table E. NaOH Sodium Hydroxide Ammonium Nitrite Potassium Permanganate KMnO 4 (NH 4 )(NO 2 ) Ni 2 (CrO 4 ) 3 Nickel (II) chromate
What would the oxidation number be for Iron in the following compounds: Fe 2 O 3 FeS
You must look at the types of atoms and their electronegativity differences. Ionic - bond between a metal and a non-metal Electronegativity difference should be = to or > than 2.0 This means that one atom can pull an e - from another atom Results in the formation of ions Mn + F = 2.4 K + O = 2.6 Big Dog vs Little Dog
Metal + nonmetalIonic bond Further apart on the Periodic table Higher ionic character Greater difference in electronegativity High ionic character Higher ionic character =
Writing Formulas Lab
What are the formulas for the following compounds: Sodium thiocyanate Ammonium oxide
Compound Naming Race
Writing Formulas Lab
What type of bonds are in the following compounds? Calcium Bromide Sulfur Oxide
You must look at the types of atoms and their electronegativity differences. Covalent - bond between two non-metals Electronegativity difference should be less than 2.0 This means that one atom is not able to pull an e - away DOES NOT FORM IONS!!! Two of the same sized dogs C+Cl = 0.6 I+I 2.7- = 0.0
Covalent - bond between two non-metals Specific Types Polar Covalent Electronegativity differences of 0.5 – the unequal sharing of e - Fe 2 O 3 = 1.6 Results in partial charges on the atom Non-Polar Covalent - the equal sharing of e - Electronegativity differences of 0.0 – 0.4 Usually only in diatomic molecules O2O2 3.4- = 0.0
Nonmetal + nonmetal Covalent bond Small difference in electronegativity Ternary substance - compound containing polyatomic ion Polyatomic ion is covalently bonded together Bond between polyatomic ion and atom is ionic MgSO 4 covalent Ionic Results in a compound having both IONIC and COVALENT bonds
Metal + MetalMetallic bond Alloy - Different metal atoms mixed together Brass – = sea of electrons Electrons are free to move all over, not bound to one nucleus Bronze –copper and tin copper and zinc Gold – Gold, silver, copper
Ionic compounds can also be drawn as Lewis structures. Positive ion Cation Since all the valence electrons are removed, no valence electrons are shown. Na Negative ion Anion The charge is written above + The added valence electrons indicate a full valence shell. Cl Brackets are added and the charge is written on the outside -
Ionic compounds Write the positive ion next to the negative ion, and include their charges Na + Cl -
Covalent compounds First write element symbols and then draw their valance electrons. H2OH2O H H O Now move the atoms to pair up any unpaired electrons H H O
CO 2 Give the formula and dot diagram for the compound formed from the following compound: EN difference ?
Fluorine and Magnesium Give the formula and dot diagram for the compound formed from the following elements: EN difference ?
Strontium and Bromine Give the formula and dot diagram for the compound formed from the following elements: EN difference ?
NH 3 Give the formula and dot diagram for the compound formed from the following elements: EN difference ?
Sodium hydroxide Give the dot diagram for the compound:
Give the formula and dot diagram for the compound formed from the following elements. Phosphorus and Chlorine P δ-δ- δ-δ- δ-δ- δ+δ+ Cl
What are they? The attractive force between the hydrogen attached to a highly electronegative atom of one molecule and a highly electronegative atom (N, O, F only) of a different molecule. Only found in polar covalent compounds Individually a very weak bond
Very High M.P. and B.P. Less dense as a solid High Heat of Vaporization Sweating, climate moderation High Surface Tension Unique properties of water Fewer molecules to be attracted to therefore a stronger attraction
Hydrogen bonding is the strongest of the intermolecular bonds!!!! Hydrogen bonding is the strongest of the intermolecular bonds!!!! (click for video)
Strontium and Iodine Give the formula and dot diagram for the compound formed from the following elements: Sr I I +2
BUBBLES The Jesus lizardThe Jesus lizard – the Basilisk lizard scroll down to view movie
Rules are similar to ionic compounds, just need to add prefixes for the number of atoms mono- di- tri- tetra- penta- hexa- hepta- octa- nona- deca-
Try the following: CO 2 CCl 4 Dinitrogen monoxide Diphosphorus pentoxide Carbon dioxide Carbon tetrachloride N2ON2O P2O5P2O5
Naming Covalent Molecules wkst 1
A.State evidence that indicates that NH 3 has stronger intermolecular forces of attraction than CF 4. B.Draw the lewis dot diagram for CF 4. Is it a polar or non-polar molecule Physical Properties of CF 4 and NH 3 at STP CompoundMP (ºC)BP (ºC)Solubility in 20ºC CF Insoluble NH Soluble
Molecules - are only covalently bonded Polarity of molecules - - completely dependent on the shape of the molecule A molecule is either polar or non-polar with respect to charge - molecules are only polar if they have polar covalent bonds - if you can draw one straight line and all the (+) are on one side and all the (-) are on the other side, the molecule is polar DipoleMolecule which has a + side and a - side
Assigning + and - to atoms The atom with the higher electronegativity gets the - The atom with the lower electronegativity gets the + Examples O == C== O H--Cl N H H H -+- nonpolar + - polar polar Symmetrical charge distribution Equal distribution of charge - results in the formation of a Nonpolar molecule Asymmetrical charge distribution Negative(-) end and Positive(+) end - results in the formation of a Polar molecule
Molecular Polarity wkst
Explain, in terms of electrons, why the bonding in NaCl is ionic?
Dissolve in polar solvents Dissolve in non-polar solvents Dissolve in polar solvents
A substance containing free ions that makes the substance electrically conductive The process where ionic compounds split (separate) into their respective ions
Draw the Dot Diagrams for the following compounds and determine if they are polar or non-polar, and name them: H 2 O CH 4
Connectors # Needed Spheres Sticks6Black2 Red2 Springs4Yellow4 You might have to share with another group to get 4. Green1 Blue1
III. VSEPR ClassShapeModelExample AXLinearHCl AX 2 Linear CO 2 AX 3 Trigonal Planar BH 3 AX 4 Tetrahedral CH 4 : AX 3 Pyramidal NH :AX 2 BENT H2OH2OH2OH2O
What are the names of the following compounds: CoI 3 MgSO 4
A substance will conduct electricity IF it has freely moving charged particles Particles can be ions, electrons, etc. as long as they can move MetalConducts electricity in solid or liquid form Freely moving electrons allows the electricity to flow. Ionic substanceDoes NOT conduct in solid form Ions are locked in place Has charges, but not free moving LiquidWhen melted, can conduct electricity Ions are mobile enough to move past each other
SolutionIn solution, ions separate Ions are free to move, conducts electricity Dissociate Covalent SolidDoesn’t conduct electricityNo charged particles LiquidDoesn’t conduct electricity No charged particles Solution Some types of covalent molecules can be broken down to make ions Ionization Conducts some electricity, because only a few of the molecules in the sample are broken down
Used to determine a substances properties – only found in covalently bonded substances Used to determine a substances properties – only found in covalently bonded substances Relatively weak compared to ionic, metallic, and even covalent bonds Relatively weak compared to ionic, metallic, and even covalent bonds Examples Examples Dispersion forces – for your college education Dispersion forces – for your college education Dipole-Dipole forces – again something for college Dipole-Dipole forces – again something for college Hydrogen bonding – we’ve done these Hydrogen bonding – we’ve done these Molecule-ion attractions – we’ll look at these Molecule-ion attractions – we’ll look at these
Molecule-Ion Attractions – the attraction between the ions and molecules of water in a solution A Good Animation A Good Animation
Ionic Hard Good Conductors Not as solids High MP & BP Dissolve in Polar Substances - water Covalent Generally soft Poor Conductors No charged particles Low MP & BP AKA – Molecular Substances
Coordinate Covalent Bond Hydronium ion Ammonium ion - one atom donates BOTH electrons that are shared O H H +H + H O HH + N H H +H + H N H H H H +
2. Dispersion Forces – weak IMF between non-polar molecules - formation of temporary polarity Bigger molecule = Stronger force He, Ne Ar or Kr
We know how atoms are held together as molecules How are molecules held together when they are liquid and solids? Dipole Interaction Polar bondHas a + side and a - side O -- H - + Look at the whole H 2 O molecule H O H We can divide this molecule into a + side and a - side This is called aPOLAR moleculeOr a DIPOLE
Molecular Polarity handout
Lab Check in
Structure Determination by VSEPR Water, H 2 O TETRAHEDRAL The electron pair geometry is TETRAHEDRAL The molecular geometry is BENT. 2 bond pairs 2 lone pairs
Affect on Boiling Points Stronger force = Higher Boiling Point
Give the name of a substance that can NOT conduct electricity in the solid phase but can as a liquid. Explain why.
Name the following compounds: PCl 3 K 2 C 2 O 4
Covalent bonds are classified as single, double, or triple bonds depending on the number of electrons shared between the two nuclei.
Intermolecular Forces 11.2 Intermolecular forces are attractive forces between molecules. Intramolecular forces hold atoms together in a molecule. Intermolecular vs Intramolecular 41 kJ to vaporize 1 mole of water (inter) 930 kJ to break all O-H bonds in 1 mole of water (intra) Generally, intermolecular forces are much weaker than intramolecular forces. “Measure” of intermolecular force boiling point melting point H vap H fus H sub
What are the names of the following compounds: KCH 3 COO BaCr 2 O 7
Types of Intermolecular Forces 3. Dipole-Dipole Forces Attractive forces between polar molecules Orientation of Polar Molecules in a Solid 11.2
Draw the electron dot diagram for the following : Magnesium Iodide ion
Sodium Atom Chlorine Atom Total charge Atom is considered Total charge Atom is considered neutral a positive ion -18 Called a Cation a negative ion Called an Anion Cation Anion Positive ion due to the loss of electrons Negative ion due to the gain of electrons meow.
Examples - Determine the type of ion shown and explain how it was made from a neutral atom. IonType of IonHow it was made K + Ca +2 O -2 Br - cationLost 1 electron cation anion Lost 2 electrons Gained 2 electrons Gained 1 electron
Draw the electron dot formula for neutral atoms of Na and F Na F All atoms want a full octet in their valence shell. This is a stable configuration. When ionic bonding occurs,the one valence electron in Na is transferred to F + - Notice how both atoms have a full octet? F has gained an electron to get a total of 8. Na uses its full shell underneath as a full valence Na The attraction between the + and - ion causes the bond ReviewIonic bonds 1. Electrons are transferred 2. Ions are created Cation lost e-, anion gained e- 3. Very strong bond. Has high melting and boiling points, and a very rigid structure 4. Creates ionic substances
Covalent Bonds a. Electrons in bonds - No transfer of electrons - Electrons are shared between valence shell of atoms - Weaker bonds than ionic In covalent bonding, atoms get a full octet by sharing electrons between their valence shells Hydrogen and helium do not need 8 electrons, only 2 H H So the molecule H 2 looks like H
In covalent bonding, atoms still want to achieve a noble gas configuration But rather than losing or gaining electrons, atoms now share an electron pair. The shared electron pair is called a bonding pair The octet rule
Look at the parts of H 2 O HH OO H H This indicates that H 2 O looks like H---O | H Not H--O--H Or H--H--O Review In a covalent bond, electrons are shared between valence shells There is NO transfer of electrons, so no ions are formed Their bonds are weaker, have lower melting and boiling points If atoms are covalently bonded, they make