Chemical Bonding - created from Mind Map_1

Energy Levels Energy levels (shells)- the electrons that surround the nucleus of an atom the period number of an atom(horizontal rows) correspond witht he number of energy levels in that atom Energy level diagrams known as Bohr diagrams how to determine # of electrons in an atom?- it is the same as the atomic # Ions must have full energy levels Aragon doesnt form ions bc its energy levels are aledeardy full Atoms form ions to get full energy levels 1st anergy level: 2 electrons 2nd energy level: 8 electrons 3rd energy level: 8 electrons

Lewis Dot Diagram Valence Electrons are in the outer shell--> determines charge The # of the vertical column correspond with the # of valence e- There are 4 valence orbitals for each atom # of protons & as # of electons is same as atomic # # of neutrons= mass # - atomic # Can hold between 0-2 electrons electrons occupy empty orbitals before pairing

Ionic Compounds form from collision between elements results in TRANSFER of e- one element loses an e- to form a cation (+), the other element gains e- forms anion (-) electrostatic force- attracts cation and anion to each other Properties How do we show an e- has transfer has occured?- square brakets w/ charge movement what does the chemical formula chow us for ionic compounds?- simplest ratio of the compound cation to anion that exists Crystal- an arrangement of ions in repeating unit The arrangement of cations and anions depends on the charge and the number of the ions Lattice- the specific ways in which atoms are arranged in an ionic compound ion- the simplest repeating unit of a crystal structure 1) Do NOT consist of molecules (bonds of ions) 2) Bonds are strong (attractive forces are stronger than repulsive) 3) Have distinct properties (high melting/boiling point) 4) Liquid & dissolve salts, conduct electrce current (charged molecules are free to move) 5) They are hard&brittle->developes fracture (resists large force) (reapeating pattern forming layers if shifts into cleavage plane

Electronegativity electronegativity- the relative ability of an atom to attract a pair of binding e- in its valence level each element is assigned an e-neg based on a scale developed by Linus Pauling Matals have low e-neg Non-metals have high e-negs the DIFFERENCE in e-negs between the matal and non-metal that gives the bonds between their ionic character Ex. oxygen: 3.5

Covalent compounds Electrons Bonding capactiy Formatopn of Covalent Bonds Lewis structure steps 1 e- in an orbital is an unpaired/bonding electron, can be shared w/another atom 2 e- in an orbital non-bonding/lone pairs Lewis dot diagrams show what e- are lone pairs and which can bond Will repell e- in other orbitals will NOT bind w/another atom the number of unpaired e- in an atom the maximum # of single covalent bonds that an atom can form Octet rule the shared e- belong to both valence levels of each atom atoms must be surrounded by 8 e- to have full valence shells Atoms must share 2 or more e- 1) Determine # of e- 2) The atom w/ lowest e-neg is the central atom 3) Distribute electrons so aech atom follows octet rule 4) repkace each pair of dots with a dash 5) Count # of electrons around each atom , must follow octet rule 6) If structure is an ion, place brackets around and indicate charge # of valence e- should be same from step 1

Multiple Bonds Covalent bonds that has 2 or 3e- pairs by two atoms called double or triple bonds

Types of formulas Empirical Molecular Lewis Structural Steriochemical shows whole # ratio of atoms shows actual # of atoms in compound uses symbols to show e- sharing &transfer of stable valence octet shows which atoms are bonded&type of bond structural formula to represent the compound in 3-D Linear- 2 bonding, most common Be or C, all on same plane Trigonal planar- 3 bonding, most common B or C, all on same plane Tetrahedral- 4 bonding, 2 on same plne 1 in front 1 behind, most common C or Si Trigonal planar- 3 bonding, 1 lone, 1 on plane 1 in front 1 behind 1 lone, common: N or P Bent- 2 bonding, 2 lone, 2 on plane 2 lone, common: O and P CARBON WILL NEVER HAVE A LONE PAIR

VSEPR Parirs of e- that surround central atom of an ion arranged as far apart as possible to minimize electron-electron repulsion Valence Shell Electron Pari Repulsion Used to predict shape of ion

Polarity of Molecules Dependant on 2 factors If molecule is only made of nonpolar bonds, then it is always nonpolar If a molecule contains polar bonds it DOESNT always mean it is polar If covalent bond is polar the e- are pulled to more e-neg atoms-> creates dipole bond The shape of a molecule determines if dipole bonds will cancel out or create polar molecule Nonpolar covalent: Polar covalent: 0.5-2.1 Ionic: >2.1 If pulls dont all cancel out then it is a polar molecule If all pulls cancel out then it is a nonpolar molecule Bond Polarity Molecular shape All tetrahedrals that have same substituents are polar molecules All trigonal pyramidals are polar molecules bents are always nonpolar molecules

Chemical Bonding