atomic structure and chemical bonding

valence electrons

electrons in the outermost shell that partipate in chemical bonding

octet rule

atoms tend to gain, lose, or share electrons to achieve eight valence electrons

covalent bond

bond formed by sharing electrons between atoms

ionic bond

electrostatic attraction between oppositively charged ions

cation

positively charged ion formed by losing electrons or gaining protons

anion

negatively charged ion formed by gaining electrons or losing protons

electronegativity

an atom’s tendency to attract shared electrons

polar covalent bond

bond in which electrons are shared unequally

nonpolar covalent bond

bond in which electrons are shared relatively equally

what determines bond polarity

electronegativity difference between bonded atoms

ionization energy

energy required to remove an electron from an atom or ion

electron affinity

energy change associated with adding an electron to an atom

orbital hybridization

mixing atomic orbitals to form hybrid orbitals used in bonding

sp3 hybridization

mixing one s and three p orbitals to form four sp3 orbitals

sp3 geometry

tetrahedral

ideal bond angle of sp3

109.5

molecular shape of typical sp3 amine nitrogen

trigonal pyramid

molecular shape of water

bent due to two lone pairs on oxygen

sp2 hybridization

mixing one s and two p orbitals to form three sp2 orbitals

sp2 geometry

trigonal planar

sp2 ideal bond angle

120

sp hybridization

mixing one s and one p orbital to form two sp orbitals

sp geometry

linear

sp ideal bond angle

180

sigma bond

bond formed by direct orbital overlap along internuclear axis

pi bond

bond formed by sideways overlap of parallel p orbitals

how many sigma and pi bonds in single bond

one sigma bond

how many sigma and pi bonds in double bond

one sigma and one pi

how many sigma and pi bonds in triple bond

one sigma and two pi

why is rotation restricted around double bond

rotation would disrupt sideways orbital overlap forming pi bond

intermolecular interactions

attractions or repulsions between molecules or different parts of molecules

hydrogen bond

attraction between h bonded to an electronegative atom and suitable electron-pair acceptor

hydrogen-bond donor (hbd)

group containing hydrogen attached to electronegative atom (commonly O-H or N-H)

hydrogen-bond acceptor (hba)

atom with available lone pair that can accept hydrogen bond

can alcohol act as both hbd and hba

yes. O-H donates and oxygen accepts

can ether act as hbd

no. has no O-H or N-H bond

can ether act as hba

yes, through oxygen’s lone pairs

can tertiary amine act as hba

no, lacks an N-H bond

can neutral tertiary amine act as hba

yes, through nitrogen lone pair

ion-ion interaction

electrostatic attraction or repulsion between charged groups

ion-dipole interaction

attraction between ion and polar molecule

dipole-dipole interaction

attraction between molecules with permanent dipoles

london dispersion forces

weak attractions arising from temporary, induced dipoles

van der waals interactions

weak noncovalent interactions associated with molecule proximity and electron distributions

hydrophobic effect

tendency of nonpolar groups to associate in water, reducing unfavorable contact with water

hydrophilic

having favorable interactions with water, often through polarity or charge

lipophilic

having an affinity for nonpolar, lipid-like environments

how do charged functional groups generally affect water solubility

tend to increase aqueous solubility through favorable interactions with water

how do large nonpolar groups generally affect lipophilicity

increases lipophilicty

why are noncovalent interactions important in drug action

they contribute to drug binding, molecular recognition, solubility, and distribution