molecular structure Flashcards
bond length (d)
nuclear separation distance (nm)
bond energy
energy required to break the bond (kJ mol⁻¹)
How many electrons form one chemical bond?
2
When atoms are the same, how do nuclei share electrons?
equally
When atoms are different, how do nuclei share electrons?
unequally
What does the unequal sharing of electrons result in?
polar covalent bond
dipole moment, µ =
charge, Q (C) x distance between charge, d (m)
What is the most electronegative element?
fluorine
What is the most electropositive element?
caesium
The smaller the atoms, the ? the bond.
shorter
The more electrons in a bond, the ? a bond.
shorter
The larger the electronegativity difference between the bonded atoms the ? the bond.
shorter
As bonds become shorter, the ? bond energy increases.
more
The more electrons in a bond, the ? bond energy increases.
more
The larger the electronegativity difference between the bonded atoms, the ? bond energy increases.
more
What structure do ionic compound form?
ionic lattices
Do ionic lattices have low or high melting points?
high
valence electrons
electrons in the highest atomic orbital
Lewis structure
visual representation of the valence electrons in a molecule
Is the central atom in a molecule often the most electronegative or electropositive?
electropositive
octet
set of 4 electrons associated with an atom
VESPR
1) Valence
2) Electron
3) Shell
4) Pair
5) Repulsion
2 electron pairs
linear
3 electron pairs
trigonal planar
4 electron pairs
tetrahedral
5 electron pairs
trigonal bipyramidal
6 electron pairs
octahedral
What is the linear bond angle?
180°
What is the trigonal planar bond angle?
120°
What is the tetrahedral bond angle?
109.5°
3 bonded pairs + 1 lone pair
trigonal pyramidal
What is the trigonal pyramidal bond angle?
107°
2 bonded pairs + 2 lone pairs
bent
What is the bent bond angle?
105°
What is the trigonal bipyramidal bond angle?
90° + 120°
4 bonded pairs + 1 lone pair
seesaw
What is the seesaw bond angle?
120°
3 bonded pairs + 2 lone pairs
t-shaped
What is the t-shaped bond angle?
90°
2 bonded pairs + 3 lone pairs
linear
What is the octahedral bond angle?
90°
5 bonded pairs + 1 lone pair
square pyramidal
What is the square pyramidal bond angle?
90°
4 bonded pairs + 2 lone pairs
square planar
What is the square planar bond angle?
90°
valence bond theory
electrons are localised in bonds between 2 atoms / localised on a single atom, usually in pairs
What are the conventions of the orbital overlap model?
1) each electron is assigned to a specific orbital
2) no 2 electrons have identical descriptions
3) the electrons obey the aufbau principal
4) only the valence orbitals are needed to describe bonding
sigma (σ) bond
1) end-to-end overlap of atomic orbitals
2) single bond
pi (π) bond
1) parallel overlap of atomic orbitals
2) double bond
triple (σ) bond
1 σ bond + 2 π bonds
What does hybridisation of atomic orbitals form?
hybrid orbitals
