Topic 4/14 - Bonding Flashcards
Quiz
Charge density
The charge per unit volume of an ionic compound.
Ionic bond
electrostatic forces of attraction between oppositely-charged ions.
How are ionic compounds formed
elements have a large difference in electronegativity.
Coordination
the number of ions that surround a given ion in an ionic lattice (3D crystalline structure)
Lattice enthalpy
The strength of the force between the ions. Depends on size and charge of ion.
Why do ions have high melting and boiling points?
Strong electrostatic attraction between ions and requires high amount of energy to break.
What 2 factors determine MP of an ionic compound
MP decreases as ionic radius increases, as the charge increases MP increases.
Volatility
Doesn’t readily escape to vapor phase due to the strong electrostatic forces of attraction. Ionic compounds have low volatility.
Ionic compounds are soluble in…
Polar covalent (water) - has a separation of charges in its structure. So, when ionic compounds are put in water, the ions are attracted to the charged water molecules so the ions dissociate in water and the lattice breaks down.
Electrical conductivity
depends on the fact that ions are able to hold a charge
Can ionic compounds conduct electricity?
Not in solid because the ions are firmly in the lattice and unable to move, and can’t carry charges. They can in aqueous or molten state due to free ions that can move and carry charges.
brittleness
ionic compounds are brittle - crystals shatter when force is applied.
ionic character
determined by the difference in electronegativity btwn atoms in the compound. Bigger difference, greater ionic character.
Polyatomic ions
Has both ionic and covalent bonding. Atoms in polyatomic ion are covalently bonded and is ionically bonded to the other ion.
Covalent bonding
electrostatic forces of attraction of attraction between the positively charged nucleus and the shared pair of electrons. Nonmetals - can form single double and triple bonds
Bond length
measure of the distance between 2 covalently bonded nuclei. Expressed in picometers (pm).
Bond strength
a measure of the energy required to break a covalent bond. measured in KJ/mol.
Coordinate covalent bonds
Differ from normal bonds in the way that in a coordinate bond, both the shared electrons are provided by one of the atoms.
single –> double –> triple bond
length decreases, strength increases
Electron deficiency
Coordinate covalent bonds can occur when one of teh atoms is electron deficient (has less electrons in the valence shell -doesn’t satisfy the octet rule - H, He, B, Be). This means the atom has a tendency to accept an electron pair from a molecule with a lone pair.
Electronegativity to find polarity
Greater electronegativity means greater attraction for electrons, so they’re pulled closer giving one atom a partial negative charge.
VSEPR
The shape of a molecule is due to repulsions between pairs of e- outside the shell of the central atom.
VSEPR bonding rules
molecules take shape to minimize repulsions. Lone pairs repel more than bonded pairs. double/triple bonds don’t repel more.
Electron domains
places where bonds have formed or can form. determines electron geometry.
