2.2 - Electrons, bonding and structure Flashcards
Give the number of electrons that can fill the first four shells
2
8
18
32
Define an atomic orbital
region around the nucleus that can hold up to 2 electrons, with opposite spins
Give the shapes of an s and p orbital
S = spherical
P = dumb-bell
How many orbitals make up the s, p and d sub-shells?
S = 1
P = 3
D = 5
How many electrons can fill s, p and d sub-shells?
S = 2
P = 6
D = 10
Define ionic bonding
electrostatic attraction between + and - ions
Why do ionic substances usually exist in the solid state?
giant ionic lattices have oppositely charged ions strongly attracted in all directions
Describe the melting point, solubility and electrical conductivity of ionic compounds
- high MP = strong electrostatic forces of attraction between oppositely charged ions
- soluble in H2O = both ionic molecules and H2O are polar
- can conduct electricity in (aq) = ions free to move and carry charge, whereas in fixed position in solids
Define covalent bond
strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
Define average bond enthalpy
average amount of energy required to break a specific (covalent) type of bond in gaseous molecules
Give the bond angles of common molecules: CH4, NH3, H2O
CH4: 109.5
NH3: 107
H2O: 104.5
Define electronegativity
ability of an atom to attract the bonding electrons in a covalent bond
Explain why some molecules have polar bonds but not a permanent dipole
symmetrical molecule so polar bonds cancel out
What do polar molecules have?
permanent dipole due to covalently-bonded atoms with different electronegativities
Name the strongest type of IMF
hydrogen bonding: needs N, O or F, and H
Name the 3 types of intermolecular forces
- London forces
- permanent dipole-dipole interactions
- hydrogen bonds
State and explain the anomalous properties of ice caused by H bonding
- ice is less dense than water = its molecules are held apart by H bonds
- relatively high MP/BP = relatively strong H bonds between molecules
What are simple molecular lattices?
covalently bonded molecules attracted by intermolecular forces e.g I2, ice
Discuss the physical properties of simple molecular lattices
- low MP = weak LFs
- insoluble = no polar bonds
- cannot conduct electricity = no ions
Describe ‘ionic lattice’
- repeating pattern
- of oppositely charged ions
Why would one molecule’s LFs be stronger than another’s, leading to a higher BP (if no other types of IMF)?
more electrons = stronger LFs
(NB: when comparing IMFs, always say they are between molecules)
Which repel more - lone or bonding pairs?
lone pairs
