Unit 4: Bonding Flashcards
Valence Shell Electron-Pair Repulsion
Theory that states that a molecule adopts a shape that minimizes repulsive forces between the bonding pairs
electronegativity
Measures an elements ability to attract bonding electrons
A more electronegtive element will “pull” electrons more strongly in a bond
Periodic trend: increases left to right and bottom to top; F is the most electronegative element (4.0) and Fr is the lowest (0.7)
He, Ne, Ar, Rn have no values because they are not known to form any bonds under normal conditions
polar bond
Convalent bond between atoms with different electronegativities - the electrons are not shared equally
Partial charges on atoms
The greater the difference in electronegativity values between the 2 elements, the more polar the bond that joins them
hydrophilic
Polar substances are hydrophilic and dissolve in water
exceptions to octet rule
- H & He are stable with 2 electrons
- B & Al are stable with 6
- Elements from periods 3-7 (e.g. sulfur) usually have 8 but 10 or 12 are possible (e.g. SF6)
- Molecules with an odd number of valence electrons - 1 must remain unpaired - generally, the element with lower electronegativity
nonpolar molecule
has a symmetrical distribution of charge (e.g. CCl4)
covalent bond
Describes the force holding atoms together in a molecular compound
Involves 2 atoms sharing 2 electrons
resonance hybrid
resonance is a concept that indicates the electron arrangement in some molecules (like O3 - ozone) aren’t represented by a single Lewis structure but by 2 or more
In reality, the actual molecule is a composite of the formulas drawn and is a resonance hybrid
molecular formula
Chemical formula for a molecular or covalent compound
A formula that indicates the actual number of atoms present in a molecule
tetrahedral structures
Contain 4 groups around the central atom
Tetrahedral
General formula: AX4
# of Bonded Atoms: 4
# of Unshared Pairs: 0
EX: CH4, CH2Cl2
Tringonal pyramid
General formula: AX3
# of Bonded Atoms: 3
# of Unshared Pairs: 1
EX: NH3, NH2Cl
Tetrahedral - bent
General formula: AX2
# of Bonded Atoms: 2
# of Unshared Pairs: 2
EX: H2O, OF2
trigonal planar structures
Contain 3 groups around the central atom
Trigonal planar
General formula: AX3
# of Bonded Atoms: 3
# of Unshared Pairs: 0
EX: BF3, BH3
Tringonal planar - bent
General formula: AX2
# of Bonded Atoms: 2
# of Unshared Pairs: 1
EX: SO2, NO2
linear structures
Contain 2 groups around the central atom
General formula: AX2
of Bonded Atoms: 2
of Unshared Pairs: 0
EX: BeCl2, CO2, HCN
chemical bond
Forces that hold atoms together in a chemcial compound
polar molecule
Has an asymetrical distribution of charge
molecular or covalent compounds
A compound composed of 2 or more nonmetals and existing in discrete units of atoms held together in a molecule; electrons are shared between atoms rather than transferred from one atom to another
Often soluble in CCl4 but not water
ionic compound
A compound consisting of cations and anions in proportions that give electrical neutrality (metal and nonmetal)
Held together by ionic bonds - the attraction between ions of opposite charge
Often soluble in water but not CCl4 (carbon tetrachloride)
nonpolar bond
Covalent bond between atoms with similar electronegativity - the electrons are shared equally
No charges on atoms
ionic bond
When atoms have very different electronegativities, the electrons are transferred (not shared)
Complete transfer of 1 or more valence electrons
Full charges on resulting ions
bond length
Distance between the nuclei in a covalent bond
The more bonds, the stronger the pull between the 2 atoms and the shorter the bond length
paramagnetic
A paramagnetic electron is an upaired electron
hydrophobic
Nonpolar substances are hydrophobic and do not dissolve in water
unit cell
Simplest 3D representation of the overall crystal lattice
organic compound functional groups
H to the right in red circle should be OH
