Test 6- Bonding Flashcards
Why do bonds form?
Energy! Atoms strive to be at lowest energy possible
Diagram that shows relationship between potential energy level and distance between atoms
Be able to draw
Chemical bond
Mutual electrical attraction between nuclei and valence (outer) electrons of different atoms. This binds the atoms together. All about valence electrons!
Model to show chemical bonding
Lewis dot diagram shows elemental symbol and bonding VE
Lewis Dot diagram basics
One dot per VE --36 4???1 7???2 --58
Stable electron configuration
- Same as nobel gas
- Elements lose or gain electrons to have the same number of electrons as a nobel gas
Octet rule
- Elements strive for 8e- in outer energy level.
- some only need 2 e- to be stable like He
- Elements in part A of periodic table
Exceptions to octet rule
- H only needs 2 e-
- B needs 6 e-
- Be needs 4 e-
Electronegativity
Relative scale 0-4, the attraction an atom has for a pair of e- in a bond
- Increases up and right
- Electrons close to each other on periodic table share electron to meet the octet rule (covalent)
Share electrons
- Similar electronegativity
- same area of the periodic table
- share e- to fufil octet rule
- covalent bond
Transfer electrons
- Different electronegativity
- far apart on the periodic table
- Ionic bond
Nonpolar covalent bond
- Perfect sharing
- Same attraction
- same electronegativity
- Electronegativity difference Range: 0-.4
Polar covalent bond
- Unequal sharing
- Range: .4<_1.9
Ionic bond
- Not sharing
- Complete transfer
- Range: above 1.9
Drawing Ionic bonds
- Draw lewis dot for both elements
- transfer to make 8
- Write both elements with brackets
- Indicate the charge
- Might have to draw more than one to make 8
Characteristics of Ionic compounds
- Simplest piece is a Formula unit
- Crystal lattice AKA ionic latice
- Always solid at room temperature
- Soluble in water
- Conducts electricity
- High melting point
Formula Unit
Simplest ration of the ions
Crystal lattice AKA ionic latice
- Cluster of Na+ and Cl- Na+Cl-Na+Cl- Cl-Na+Cl-Na+ Na+Cl-Na+Cl- - Not smooth
Ionic compounds solids at room temperature
So strongly attracted that it takes a lot of energy to separate
Ionic compounds soluble in water
Water has a great attraction to the compound and the high energy breaks them apart. (Brad Pitt and Angelina Jolie)
- NaCl(s) –> NaCl(aq)
Ionic compounds conducting electricity
- Solution of ions and liquid ionic compounds
- has to be s solution or melted/liquid
- Triangle of battery, light, and beaker with solution with wires going into the solution
Nomenclature
- Naming/writing formulas
- IUPAC- International Union of Pure and Applied Chemists
Naming Ionic compounds
- Binary
- Name metal first
- When writing a formula, the net charge for all compounds is zero
- Subscript indicates number of atoms/ions of the element it follows
- Criss cross- use charge as subscript of other element
Binary
- Ionic
- 2 elements
- Metal and nonmetal
- End in ide
- name nonmetal and change ending to ide
Naming transitional metals
Use roman numerals to indicate charge of metal ion
Tertiary Ionic compounds
- More than 2 elements
- cation(+)/anion(-)
- Don’t end in ide
- All contain polyatomic ions
Naming representative metals
- more than 2 elements
- Name metal and name polyatomic ion
- Subscript doesn’t matter
- Not all compounds that end in Ide are not binary but all binary compounds end in ide
- If you have more than one polyatomic ion, it must be in parenthesis
Transitional metals with polyatomic ions
Use roman numerals to indicate charge
Covalent bonds
- Occur between 2 nonmetals (in general)
- 2 types of covalent bonds based on electronegativity difference
- 0-.4= nonpolar covalent bond, equal sharing
- 0<_1.9= polar covalent bond unequal sharing
- Exist as individual molecules
- Molecule=smallest piece of covalently bonded particle
Smallest piece of covalent vs. Ionic
- Covalent= molecule
- Ionic= Formula unit
Representing e- sharing covalent bond with a lewis dot diagram
- Still all atoms strive for 8e-
- No transfer
- No charges or brackets
- Dots and circles
- Covalent bond is the overlap
- e- always shared in pairs
- Single if one pair is shared
- Double if two pairs are shared
- Triple if three
Line structure
Each line represents a pair of electrons
Lewis Dot for polyatomic ions
- have circles (2 nonmetals) and brackets (charge)
- Lower electronegativity goes in the middle
- Add/subtract electrons according to charge
Coordinate covalent/Dative bonds
Both shared electrons are from one element
Lewis Dot and Line are both
structural diagrams
