Bonding Flashcards
What is a dative bond
A bond where the shared pair of electrons in a covalent bond come from one atom
How do we display a dative bond
With an arrow in the direction towards the atom accepting the electrons
What are the conditions for a dative bond to form
The atom that is donating must have a lone pair, and the other must have space to gain two electrons (6 electrons in outer shell)
What is an ionic compound
Oppositely charged ions held together by electrostatic forces of attraction
What is electronegativity
The tendency for an atom to attract the pair electrons in a covalent bond
When does a permanent dipole form
When there is a difference in electronegativity between two atoms in a molecule , meaning the delta negative end of one molecule is attracted to the delta positive end of the adjacent molecule
What determines the strength of a permanent dipole
The difference in electronegativity between atoms in a molecule
Explain the 4 stages as to how van der waals forces occur
- Electrons move around randomly in an oscillating motion
- If at any moment in time there are more electrons on one side of an atom, the side with more electrons will be delta negative (causing a temp. dipole)
- This will force electrons on neighbouring atoms to repel (induced dipole).
- The attraction between the atoms due to the dipoles is called VDW
Can VDW forces occur between molecules?
Yes
What are the 2 conditions for not having a permanent dipole when atoms aren’t identical in a molecule
- Molecule must be symmetrical (dipoles cancel)
- All the surrounding atoms are the same in the molecule
Give 3 characteristics of giant ionic structures
Regular structure
Cubic shape
Giant repeating pattern
Give 4 characteristics of graphite
Layers slide
Conduct electricity
Low density (layers far apart)
High melting point
What is H bonding between
H bonding is between the lone pair on N, O, F and a delta positive hydrogen
What determines the strength of a H bond
The more electronegative the atom bonded to the hydrogen, the more delta positive the hydrogen will be due to greater pulling of electrons towards N, O, F
Why doesn’t Cl form H bonds
The p orbitals that the electrons are in are of less dense negative charge
What type of I.M.F do we get when a molecule has no dipole
VDW forces
When do VDW forces get stronger
When there are more electrons (bigger atom/molecule)
What type of IMF do we get when a molecule has a dipole
Either H bond
OR
Permanent dipole
Why does H2O have more bonding pairs than H-F
- Per mole H2O will form more H bonds as there is a 1:1 ratio between lone pairs and hydrogens
- In H-F, the number of H’s will limit the number of L.Ps which can attract, due to there being more L.Ps than Hs
What holds a metallic lattice together
Sea of delocalised electrons holding positive cations
What does VSEPR say
Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repilsion
Write the order or repulsion strength between lone pairs and bonding pairs
LP-LP repulsion > LP-BP repulsion > BP-BP repulsion
What is the name of the shape with 2BPs 0LPs (Draw too)
Linear
What is the name of the shape with 3BPs 0LPs (Draw too)
Trigonal Planar
