Chapter 6 Flashcards
What is the electron-pair repulsion theory?
1) electron pairs repel so they are arranges as far as possible
2) arrangement of electron pairs minimises repulsion and holds bonded atoms in shape
Is a lone pair of electrons closer or further to the central atom, than a bonded pair?
closer
Does a lone pair of electrons repel more strongly or less strongly than a bonded pair?
more
What is the relative repulsions between lone pairs and bonding pairs?
bonded-pair/bonded-pair < bonded-pair/bonded-pair < lone-pair/lone-pair
What is the name of the shape with 4 bonded pairs and 0 lone pairs?
tetrahedral
What is the name of the shape with 3 bonded pairs and 1 lone pair?
pyramidal
What is the name of the shape with 2 bonded pairs and 2 lone pairs?
non-linear
What is the bond angle of 4 bonded pairs and 0 lone pairs?
109.5
What is the bond angle of 3 bonded pairs and 1 lone pairs?
107
What is the bond angle of 2 bonded pairs and 2 lone pairs?
104.5
What is the name of the shape with 3 bonded pairs and 0 lone pairs?
trigonal planar
What is the bond angle with 3 bonded pairs and 0 lone pairs?
120
What is the name of the shape with 2 bonded pairs and 0 lone pairs?
linear
What is the bond angle with 2 bonded pairs and 0 lone pairs?
180
What is the name of the shape with 6 bonded pairs and 0 lone pairs?
octahedral
What is the bond angle with 6 bonded pairs and 0 lone pairs?
90
Why does electronegativity change when the bonded atoms are different elements?
1) nuclear charges are different
2) atoms may be different sizes
3) shared pair of electrons may be close to one nucleus
What is electronegativity?
the attraction of a bonded atom for the pair of electrons in a covalent bond
Does nuclear charge increase or decrease across the periodic table?
increase
Does atomic radius increase or decrease across the periodic table?
increase
Does electronegativity increase or decrease across the periodic table?
increase
Does electronegativity increase or decrease up the periodic table?
increase
If the electronegativity difference is 0, what is the bond type?
covalent
If the electronegativity difference is 0-1.8, what is the bond type?
polar covalent
If the electronegativity difference is >1.8, what is the bond type?
ionic
When is a bond non-polar?
1) bonded atoms are the same
OR
2) bonded atoms have same/similar electronegativity
Do non-polar solvents mix with water?
no
What is the separation of opposite charges?
dipole
What is a permanent dipole?
a dipole in a polar covalent bond
Why is a carbon dioxide, CO₂, molecule non-polar?
1) C=O bonds have a permanent dipole
2) dipoles act in opposite directions
3) dipoles cancel and overall dipole is 0
What are intermolecular forces?
weak interactions between dipoles of different molecules
What are the types of intermolecular forces?
1) induced dipole-dipole interactions (London forces)
2) permanent dipole-dipole interactions
3) hydrogen bonding
Are London forces strong or weak?
weak
Do London forces exist between all or some molecules?
all
What do London forces act between?
induced dipoles
What is the origin of induced dipoles?
1) instantaneous dipole exists at any instant
2) instantaneous dipole induces dipole on neighbouring molecule
3) induced dipole induces further dipoles on neighbouring molecules
Are induced dipoles permanent or temporary?
temporary
The more electrons in a molecule, the … the instantaneous and induced dipoles.
larger
The more electrons in a molecule, the … the induced dipole-dipole interactions.
greater
The more electrons in a molecule, the … the attractive forces between molecules.
stronger
What do permanent dipole-dipole interactions act between?
permanent dipoles in polar molecules
What are the molecule in a simple molecular lattice held in place by?
weak intermolecular forces
How are the atoms within each molecule of a simple molecular lattice bonded?
strongly by covalent bonds
How can the weak intermolecular forces in a simple molecular lattice be broken?
by the energy present at low temperatures
Do simple molecular substances have low or high melting and boiling points?
low
When a simple molecular lattice is melted, what breaks?
only weak intermolecular forces
Are simple molecular substances soluble or insoluble in non-polar solvents?
soluble
Are simple molecular substances soluble or insoluble in polar solvents?
insoluble
Why are simple molecular substances insoluble in polar solvents?
1) little interaction between molecules in lattice and solvent molecules
2) intermolecular bonding in polar solvent too strong to be broken
Why can polar covalent substances dissolve in polar solvents?
polar solute molecules and polar solvent molecules attract each other
Are simple molecular structures conductors or non-conductors of electricity?
non-conductors
Why are simple molecular structures non-conductors of electricity?
1) no mobile charged particles
2) can’t complete an electrical circuit
What is a hydrogen bond?
1) special type of permanent dipole-dipole interaction
Hydrogen bonds are found in molecules containing what?
1) electronegative atom with lone pair of electrons
2) H-atom attached to electronegative atom
What are the electronegative atoms with a lone pair of electrons that undergo hydrogen bonding?
1) nitrogen
2) oxygen
3) fluorine
What are the strongest type of intermolecular attractions?
hydrogen bonds
How is a hydrogen bond shown?
dashed line
Is ice more or less dense than water?
less
Why is solid ice less dense than liquid water?
1) hydrogen bonds hold water molecules apart in open lattice structure
2) water molecules in ice further apart than water
3) solid ice less dense than liquid water + floats
Does water have a high or low melting and boiling point?
high
Why does water have a high melting and boiling point?
1) hydrogen bonds are extra forces, over London forces
2) large quantity of energy needed to break hydrogen bonds in water
