topic 2: bonding and structure Flashcards
define ionic bonding
the strong electrostatic attractionbetween oppositely charged ions
explain how ionic radius effects ionic bonds
smaller radius = stronger bond. electrostatic attraction decreses with distance
explain the increase in ionic radius down group 1
same charged ion but increasing number of shells
explain the decrease in ionic radius across a period with isoelectronic ions
same structure of electrons but more protons further to the right
why do ionic solids only dissolve in polar solvents
because the ions are charged they can be separated if the new bonds formed with the solvent are stronger
why cant ionic solids be shaped
when the layers slide over one another, like charged repel and the solid breaks apart
define covalent bonding
the strong electrostatic attraction between two positive nuclei and the shared pairs of electrons in the bond
what effects bond length and bond enthalpy in a covalent bond
the higher the electron density between the atoms, the greater the attraction. greater attraction reduces bond length and increase bond enthalpy. (more electrons in bond)
define electronegativity
the ability of an atom to attract the bonding electrons in a covalent bond
how does electronegativity change across the periodic table
increases across period
decreases down the group
what increases electronegativity. 2
higher nuclear charge
smaller atomic radii
why can covalent bonds be polar
uneven electronegativities so charge of shared electrons are ditributed towards one of the atoms causing partial charges in the mollecule
describe london forces
electrons move randomly around atoms and cause instantaneous dipoles. this dipoles interact with other attoms causign a week force of attraction
what effects the strength of london forces
larger electron clouds = stronger forces
greater surface area = stronger forces
how do the shapes of organic mollecules effect the strengh of london forces
longer chains = more contact = stronger
more branches = cant pack closely together = weaker
describe permenant dipole permenant dipole interactions
weak electrostatic forces of attraction between 𝛿+ and 𝛿- of different polar mollecules.
explain how hydrogen bonding works
due to the electronegativity of oxygen, nitrogen and fluorine, they draw the bonding electrons away from the hydrogen atom. the hydrogen has such a high charge density that its form weak bonds with lone pairs on the other atom (NOF)
why does ice float on water
ice is less dense because lattice structure has a lot of empty space
why are alcohols less volitile than similar alkanes
the polar hydroxyl group allows hydrogen bonding between adjacent oxygens and hydrogens
when do solvents work
when the bonds that form between the solvent and the substance are the same or stonger the substance will dissolve
