Chemistry- Bonds Flashcards
(32 cards)
chemical bond
- forces that hold groups of atoms together and make them function as a unit
- forms if the energy of the aggregate (combined product) is lower than that of the separated atoms
chemical bonding
a mutual electrical attraction between the nuclei and valence electrons of different atoms that bond them together
ionic bonding
- electrons are transferred
- metal & nonmetal
- electronegativity range is 1.7 and greater
covalent bonding
- electrons are shared equally
- nonmetal & nonmetal
- electronegativity rand 0-1.69
- one with higher electronegativity (-)
nonpolar covalent bonding
- equal sharing of electrons
- electronegativity range: 0 - 0.4
polar covalent bonding
- unequal sharing of electrons
- electronegativity rand: 0.5 - 1.69
coordinate covalent bonding
both the shared electrons come from the single atom
metallic bonding
- metals can be thought of positive ions immersed in a “sea” of mobile electrons
- ONLY IN METALS
- valence electrons are shared between all atoms
- constantly IN MOTION
crystal lattice
3-D network of cations and anions mutually attracted to one another
formula unit
ratio of atoms in the crystal lattice in simplest ratio
ionic compounds
- mostly solids (bonded very tightly)
- high melting and boiling point
- brittle
- conduct electricity when MOLTEN/ DISSOLVED IN WATER
- soluble in water, insoluble in organic solvents
molecular compounds
- solids, liquids, or gases
- low melting and boiling point
- soft
- non conductors
- insoluble in water, soluble in organic solvents
dipole moment
- determined by shape of molecule &polarity of bonds
- property of a molecule whose charge distribution can be represented by a center of - and +charge
- represented by arrows
- positive –> negative (points to negative)
nonpolar molecules
- molecules with nonpolar covalent bonds and all monoatomic (Cl2, N2, H-H, Cl-Cl)
OR - molecules with polar covalent bonds with symmetrical charge (CO2, BF3, CCl4)
- no poles
polar molecules (dipoles)
- molecules with polar covalent bonds with asymmetrical charges
- will have a positive end and negative end
presence of oppositely charged ends produces
- force of attraction which
- increased BP and MP
- higher heat of fusion (melting) and vaporization
- low V.P.
HF
- predicted to be ionic but is actually COVALENT
- due to HYDROGEN BOND
BF3
- predicted to be ionic but is actually COVALENT
- due to SYMMETRY
LiH or NaH
- predicted to be covalent but is actually IONIC
- due to HYDRIDES
lewis structure
- shows hoe valence electrons are arranged among atoms in a molecule
- stability relates to noble gas configuration
duet rule
hydrogen forms stable molecules when it shares 2 electrons
octet rule
elements form stable molecules when surrounded by 8 electrons
Exceptions To Octet Rule
- molecules with odd number of electrons
- molecules in which an atom has less than an octet (B and Be)
- molecules in which an atom has more than an octet (P and S/ third period onward)
- second elements never exceed octet rule
- C, N, O, F obey octet rule
VSPER (Valence Shell Electron-Pair Repulsion)
- structure around a given atom is determined principally by minimizing electron pair repulsion
- (un)shared pair of electrons repel each other
- an unshared pair repels more strongly than shared pair
- double and triple bond are considered as a single bond
- shape of molecule is result of (un)shared electrons being placed as far as possible
