Unit 1: Bonding (Textbook) Flashcards
D: Octet rule
Eight electrons filling the valence level = stable
D: Valence orbital
The volumes of space that can be occupied by electrons in an atom’s highest energy level.
D: Electronegativity
Relative ability of an atom to attract a pair of bonding electrons in its valence level.
D: Covalent bond
- Forms between two nonmetals
- The attraction between two nuclei for a shared pair of bonding electrons.
D: Ionic bond
The attraction between a specific cation and anion.
Why do ionic bonds form a crystal lattice?
When enough ions assemble to form a visible amount of compound, we are able to see a repeating crystal shape.
D: Metallic bonding
When both types of colliding atoms have relatively low electronegativities, the atoms share electrons but no chemical reaction takes place.
5 Properties of a metallic bond
Shiny Malleable Conductor Crystal lattice Low e/n
In metallic bonds, why are valence electrons free to move between the atoms?
The valence electrons are not held strongly by their atoms
Describe the phrase “sea of mobile electrons”
Wherever the electrons move in a metallic bond, they hold the atoms together. The “glue” that holds the structure together
Why are metallic bonds malleable?
The atoms can be moved around each other without moving them further apart from each other so the bonds are not weakened or broken by the changing shape of the solid.
VSEPR Theory (5)
- Only the valence electrons on the central atom are important for molecular shape
- Valence electrons are paired
- Bonded/lone pairs of electrons are treated equally
- Valence electrons pairs repel
- Molecular shape is determined by the positions of electron pairs when they’re a max distance apart
D: Polar molecule
Negative charge is not distributed equally among the atoms = partial positive and negative charges on opposite sides of the molecule
D: Nonpolar molecule
A molecule with symmetric electron distribution
D: Nonpolar covalent bond
If the bonded atoms have the same electronegativity they will attract any shared electrons equally
D: Polar covalent bond
If atoms have different e/n
If x > 1.7
Ionic
If x < 1.7
Polar covalent
If x =0
Nonpolar covalent
D: Bond dipole
The charge separation that occurs when the e/n difference of two bonded atoms shifts the shared electrons making one end negative and the other positive
Explain “like dissolves like”
Nonpolar solute dissolves in nonpolar solvent. Vice versa.
D: Intermolecular forces
The forces of attraction and repulsion between molecules
What are “van der Waals” forces?
DD
LDF
Properties of DD forces
- Attraction between dipoles
- Weakest IMF
- Only for polar molecules
LDF
Electron movement within a molecule produces a momentary dipole
D: Isoelectronic molecules
Molecules with the same number of electrons
D: Hydrogen bond
- Hydrogen with fluorine, nitrogen or oxygen
- Strongest IMF
Why is water more dense than ice?
Water contracts when freezing. HB hold water molecules in a hexagonal lattice = low density
Where are ionic compounds abundant in nature?
Fresh and salt water
5 Properties of ionic compounds
- Rigid structure
- Solid at room temp.
- High bp and mp
- Crystal lattice
- Brittle
Why are ionic compounds brittle?
Rigid structure = ions cannot be rearranged without breaking the ordered structure of the crystal lattice
5 Properties of metals
Shiny Conductor Malleable Low to high bp Crystal lattice
Bonding Theory in metals (3)
- Low e/n = loosely held electrons
- Empty valence orbitals = electron mobility
- Electrostatic attraction between positive ions and negative electrons = strong bonds
Why are metals lustrous?
Valence electrons absorb and re-emit light
Why are metals malleable?
Nondirectional bonds mean that planes of ions can slide over each other while remaining bonded
Why are metals able to conduct electricity?
Valence electrons can freely move throughout the metal
Why do metals form a crystalline structure?
Electrons provide the “electrostatic glue” holding the metal ions together producing structures that are continuous and closely packed
Properties of molecular solids
- Not conductors (in pure form and solution)
- Relatively low mp
- Not very hard
Why can’t molecular compounds conduct electricity?
Individual entities are neutral
2 Examples of covalent network crystals
Diamond
Quartz
Properties of covalent network crystals
- Very hard
- Brittle
- Very high mp
- Insoluble
- Not conductors
Why are covalent network crystals considered brittle?
Do not bend under pressure
Describe covalent network crystal shape of a diamond
Carbon atoms in a large tetrahedral network with each carbon covalently bonded to four other carbon atoms
Why are covalent network crystals so hard?
Interlocking structure meaning atoms are not easily displaced
Why do covalent network crystals have such high melting points?
Many covalent bonds need to be broken which requires a lot of energy
3 Properties of molecular crystals
- Soft
- Low mp
- Nonconducting (solid, liquid and solution)
Forces/bond in molecular crystals
LDF
DD
HB
5 Properties of metallic crystal
- Soft to very hard
- Conductor (solid and liquid)
- Ductile
- Malleable
- Lustrous
3 Properties of ionic crystal
- Hard, brittle
- Medium to high mp
- Conductor (solid and solution)
3 Examples of covalent network crystal
C(s)
SiC(s)
SiO2(s)
