bonding Flashcards
outline the structure of a metal
Metals are a net of cations surrounded by a sea of delocalised electrons.
referring to the structure of a metal, why are they malleable and ductile and conductive
Valence electrons breaks away from the atoms, leaving behind positive ions and move randomly through the lattice, allowing for electrical conduction.
Electrons act as a glue so that metals are malleable and ductile.
boiling point of metal generally is?
high
melting point of metal generally is?
high
why do metals maintain their lattice structure
strong electrostatic forces between cations and delocalised electrons
define covalent bonding
when two or more elements bond via the sharing of electrons usually non-metals
define ionic bonding
Electrons are transferred from one atom to another forming positive and negative ions, held together by electrostatic attraction. (metals and non-metals)
define electronegativity and its uses
Electronegativity is the ability of an atom to attract shared electrons. Can be useful in determining if a bond is nonpolar covalent, polar covalent or ionic.
what is the difference in electronegativity for non polar bonds?
they will have the same electronegativity
do polar covalent bonds differ in electronegativity
yes around <2 absolute value difference in electronegativity
list the types of compounds
metallic lattices, ionic compounds, covalent molecular and covalent network/lattice
list the features of ionic lattice compounds
o Giant ionic lattices containing oppositely charged ions
o Always compounds
o Hard and brittle
o Slide so that opposite charges repel, which is why these are brittle
o When solid they do not conduct electricity, ionic solutions do though
list the features of covalent molecular substances
- strong intramolecular bonds but weak intermolecular bonds, therefore they have low melting and boiling points
- soft
- non conductive
list the features of covalent lattice substances
o Covalent bonding extends indefinitely throughout the whole crystal
- extremely strong
o Also known as covalent network
o Examples are diamond
describe how an ionic substance is written as a lewis dot diagram
the metal always comes first, simply as a
coefficient:metal:positive charge
then add the nonmetal = coefficient:non-metal with lewis dot diagram: charge: square brackets
when is a molecule non-polar
- each bond is non polar and there are no unbonded electron pairs
- no net dipole moment (all moments cancel out)
- each bond has the same polarity
Molecule is polar if:
- there is a net dipole moment
- each bond is non-polar but there are unbonded electron pairs
- bonds in the molecule have different polarities or there are unbonded electron pairs
list all types of shapes for molecules
linear, pyramidal, bent, trigonal planar, tetrahedral
describe linear shape and differentiate between polar and non polar
- non-polar means that the two atoms attached to the central atom are the same and there are no lone pairs on the central molecule
- Polar means that the two atoms attached to the central atom are different, and thus have a net dipole moment.
can a compound with only 2 elements be anything but linear
no but it can be polar e.g HCl
describe bent shape and differentiate between polar and non polar
a bent molecule is a linear molecule that has a pair of unbonded electrons in the central atom, is always olar
describe pyramidal shape and differentiate between polar and non polar
trigonal planar shape but unbonded electron pair, eg NH3 and is always polar
describe trigonal planar shape and differentiate between polar and non polar
always symmetrical, no unbonded electron pairs but can have a net dipole movement if one of the connected atoms are differen
describe tetrahedral shape and differentiate between polar and non polar
always symmetrical, can have net dipole movement, no unbonded electron pairs
the larger the difference in electronegativity?
the more polar the bond, the more attractive the substance is to electrons, the less reactive it is
describe the 3 main intermolecular forces
dispersion
dipole dipole
hydrogen bonding
list the 3 intermolecular forces from strongest to weakest
hydrogen bonding > dipole dipole > dispersion
what are dispersion forces and how do they work
Dispersion forces are attractions between negatively charged electron cloud of one molecule and the positive charged nuclei of neighboring molecules.
How do they work: since electrons move they are unevenly distributed on an atom or molecule.
This creates a temporary dipole movement, aka more electrons on one side as the electron cloud is distorted, and this creates attraction between atoms and molecules.
TEMPORARY
simple definition of dispersion force
(it catches the window of the net dipole and induces another molecule to become a dipole, creating an electro static attraction.) TEMPORARY
factors which influence dispersion force
- No. of electrons (more electrons more dispersion force)
- Size of the atom or the molecular weight (more atoms, more electrons)
- Shape of the molecule (more compact, less dispersion force)
describe dipole dipole attraction
- Dipole-dipole attraction or dipole forces are the electrostatic attraction between two polar molecules. The attraction between the partial positive on one molecule and the partial negative on the other.
describe hydrogen bonding
- Hydrogen bonding are a special case of dipole forces. This occurs between molecules in which hydrogen is bonded to nitrogen, oxygen or fluorine.
do all substances display dispersion forces?
yes, becasue the electron clouds of molecules can be distorted
