Never say I tried it once and it did not work. Earnest Rutherford 2 Lewis Electron Dot Structures
Composed of elemental symbol dots representing the outer shell or valence electrons
For oxygen --
3 Lewis Electron Dot Structures
Add or subtract dots for electrons gained or lost to form ion.
1s2 2s2 2p4 1s22s2sp6 4 Bonding
Atoms like to have a full outer shell and will gain lose or share electrons to achieve a full outer shell
Representative elements gain lose or share electrons to have 8 electrons in their outer shell corresponding to full s and p orbitals.
This is the octet rule.
5 Types of Chemical Bonds 6 Two kinds of bonds
atoms gain or lose electrons to form octet
ions held together by electrostatic forces
atoms share electrons to form octet
atoms held together by shared electron covalent bonds
7 Ion Formation
Na Na 1e
Mg Mg2 2e
Cl 1 e Cl1
S 2 e S2
These elements tend to lose electrons to gain an octet Note losing an electron always costs energy -- but sometimes this lost of energy can be compensated by the strong electrostatic energy gained when a cation and an anion combined. These elements tend to gain electrons to form an octet 8 Ionic Bonds
Bonds formed by the interaction of ions and the strong electrostatic forces that hold them together.
Ions group together in ratios which balance their positive and negative charges results in a neutral crystal
9 What compound will be formed by the reaction of potassium and chlorine 10 What compound will be formed by the reaction of magnesium and oxygen 11 What compound will be formed by the reaction of sodium and sulfur 12 What compound will be formed by the reaction of sodium and sulfur 13 Show bonding in H2O 14 Covalent Bonds
Bonds where atoms share electrons to achieve an optimum number of electrons in their outer shells. Typically an octet.
15 Show bonding in H2
or 17 (No Transcript) 18 Lewis Electron Dot Structures
Bonding electrons pairs electron pairs involved in bonds
Lone electron pairs electron pairs that do not participate in bonding
Bond order number of bonds
19 Bond Length Bond Strength
A measure of the amount of energy it takes to break a bond.
The length of a bond between two atoms is the distance separation the nuclei of the atoms.
20 Bonding in nonmetals
Generally every unpaired electron in the Lewis Dot diagram of an element can form a bond.
21 Show bonding in Cl2
22 Show bonding in O2
23 (No Transcript) 24 Show bonding in N2 25 Diatomic Elements 26 Writing Lewis Dot Structures
Decide which atoms are bonded together - draw a skeleton structure
Count the total number of valence electrons available.
Find the number of electrons needed to give an octet around all atoms -- (remember H needs 2 all else need 8).
27 Writing Lewis Dot Structures
Determine number of electrons short.
Number of bonds needed number of electrons short/2.
Distribute bonds -- (1st hook atoms together and then add double bonds where appropriate).
Calculate number of electrons used in bonds.
28 Writing Lewis Dot Structures
Calculate electrons remaining.
Distribute remaining electrons to give all atoms an octet.
29 Lewis Structures of ions
for anions add the extra electrons to the number available
for cations subtract the lost electrons from the number available
In some Lewis structures the multiple bonds can be written in several equivalent locations. All structures have the exact same energy. Which is the correct Lewis structure
Answer None alone are correct the true molecule is a hybrid of the possible structures. The electrons are delocalized.
31 Predicting Shapes of Molecules
To predict the shapes of molecules we look at the things (sigma bonds or lone pairs of electrons) surrounding them and put them as far from each other as possible.
Valence Shell Electron Pair Repulsion (VSEPR) Theory
32 2 atoms attached to central atom 33 3 atoms attached to central atom 34 4 atoms attached to central atom 35 3 atoms lone pair attached to central atom 36 2 atoms 2 lone pairs attached to central atom 37 (No Transcript) 38 Electronegativity
A measure of the relative tendency of an atom to attract electrons to itself when it is bonded to another atom.
Electronegativity increases up and to the right on the periodic table.
39 (No Transcript) 40 Polar Bonds
Bonds in which electrons are not shared equally due to the electronegativity differences.
41 Polar molecules
Molecules with a positive and negative end due to the presence of polar bonds.
42 Cl2 43 HF 44 H2O 45 CO2
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