structure and bonding in compounds Flashcards
which inter molecular forces are hydrogen bonds stronger than
london dispersion forces, and permanent
dipole-permanent dipole attractions.
in a polar covalent bond a permanent dipole is
created because the electrons are
unequally shared
the boiling point of C6H14 is greater than that of
C4H10 because C6H14 has
there are more london dispersion forces between the molecules
only _____ are found in compunds
hydrogen bonds
the unusual density of ice is caused by
hydrogen bonds holding molecules in an open network structure
the unusual boiling point of water is caused by
hydrogen bonding between molecules
metals can conduct electricity in their solid state because of their
delocalised electrons
a property of ionic substances
conduct electricity when molten or in solution
a reason why aluminium is a better conductor of electricity than sodium
each aluminium atom will ionise to produce three electrons and a Al3+ ion. Sodium will produce only one electron (to carry the electric current) from each atom
why does melting point increase as no of electrons increase
more electrons = larger temp dipole and stronger LDF forces between molc. therefore more energy required to overcome these forces
what does equally shared electrons mean
pair of electrons located at the same distance from each nucleus
pure covenant bond
- pair of electrons experience same attractive force from each nuclei as electronegativity are the same
- pair of electrons located at the same distance from each nucleus
what’s a polar bond
when unequal sharing of electrons occurs in the bond
- molc polar if has a permanent dipole
what’s a polar molecule
a molc that has a permanent slightly positive charge on one side of the molc and a slightly negative charge on the other side
how to distinguish a non-polar molc
- symmetrical
if the molc has symmetry the dipoles cancel each other out - spacial arrangement
has no side that has a positive and negative charge
how to detect polarity
by using a charged plastic rod that’s rubbed with a cloth giving it electrical charge, if stream deflected its polar if not its non-polar
to ensure fair comparison between molecules they need
similar size, shape and no of electrons
what’s permanent dipole - permanent dipole attractions
intermolecular forces of attraction between molc which have a permanent overall dipole
- stronger than LDF with similar no of electrons
what are miscible substances
liquids that dissolve in each other
what are immiscible substances
substance with stronger intermolc forces leading to its molc clustering together to form a separate layer
hydrogen bonding
electrostatic forces of attraction between molc that contain highly polar bonds - when hydrogen is bonded to a strongly electronegative element - O, N, F
where is hydrogen bonding on the strength scale
stronger than PPD and LDF but weaker than covenant bonds
viscosity
measure of how much molc tend to stick together
- more viscous more runny
how is ice less dense than water
the arrangement of water molc, held together by a network of hydrogen bonds, is strong and spaces out water molc preventing them packing closely together
