Chemical Bonding + Structure Flashcards
what is an ionic bond
- electrostatic attraction between oppositivley charged ions
- transfer of electrons
- polarity difference greater than 1.7
- usually metal + non metal (cations and anions)
what is a covalent bond
- electrostatic attraction between a pair of electrons and a positively charged nuclei
- sharing of electrons
- usually nonmetal+ nonmetal
what is metallic bond
- negatively charged metal ions are attracted to delocalized electrons
- metal + metal
what are ionic compounds
are formed when electrons are transferred from one atom to another to form ions with complete outer shells of electrons
- consist of ions held tightly together in attic structures by ionic bonds
what are polyatomic ions
ions containing more than one elements
CATIONS
metals LOSE electrons to form positive ions
ANIONS
non-metals gain electrons to form negative ions
how can charge be predicted
accorrding to position on periodic table
- transition metals can form more than one charge
properties of ionic compounds
- solids
- lattice structure
- high melting point + boiling point
- low volatility
- do NOT conduct electricity in solid state
- soluble in water
- neutrally charged due to balance of positive and negative ions
what is the goal of a covalent bond
octet rule/stability: to achieve a full shell of valance electrons
WHAT IS A MOLECULE
a group of atoms held together by covalent bonds
what happens as more bonds are added
bond length decreases and bond strength increases
what is electronegativity
the tendency of an atom in a molecule to attracted a shared pair of electrons towards itself
what is polarity
polar bonds form when two atoms bonded together have different electronegativity values (UNEQUAL SHARING)
what is VSEPR
VALANCE SHELL ELECTRON PAIR REPULSION: the total # of electron domains determine the geometrical arrangement by maximum repulsion
- ELECTRONS ARRANGE THEMSELVES AROUND A CENTRAL ATOM SO THA THEY ARE AS FAR APART AS POSSIBLE
Linear
electron domains: 2 (2 atoms bonded to central atom)
angle: 180
Bent/V-shaped
electron domain: 3 (2 atoms bonded to central atom with one or two un paired electrons)
angle: 105
Trigonal Planear
electron domain: 3 ( 3 atoms bonded to central atom)
angle: 120
trigonal pyramidal
electron domain: 4 (3 atoms and an unbonded pair bonded to central atom)
angle: 107 or less than 109.5
tetrahedral
electron domain: 4 (4 atoms bonded to central atom)
angle: 109.5
having polar bonds does not equal a polar molecule
symmetrically also is taken into account
what are intermolecular forces
the physical properties of molecular substances that result from different type of forces between their molecules
types of intermolecular forces
- van der waal forces
- london forces (dispersion forces)
- dipole-dipole forces
- hydrogen bonding
what are london dispersion forces
- temporary dipoles due to fluctuating electrical field
- electrons can be unevenly spread which lead stop temporary dipoles
trend: increase with increasing molecular mass
factors that affect the magnitude of london forces
- number of electrons
- size and volume of electron cloud
- shapes of molecules
what are dipole-dipole forces
- when dipoles attract (usually in polar molecules)
- weaker than covalent bonds
what are hydrogen bonds
- a strong type of dipole-dipole
- when hydrogen bonds to a small, highly electronegative element
F, N
strength of the forces
van der waal
melting + boiling point
are an indication of the strength of the intermolecular forces
m+ b points of covalent bonding
STRONG
m+ b point of ionic and metallic bonding
strong due to ionic attraction
the weaker the attractive forces….
the more volatile (boiling point) the substance
m/b point of intermolecular forces
h bonding > dipole-dipole> london forces
what is conductivity
substance must posses electrons.ions free to move
covalent bond conductivity
WEAK CONDUCTORS UNLESS ABLE TO IONIZE SOLUTION
Solubility
“Like dissolves like”
polar substances are more soluble in water and less soluble in non-polar substances
