Bonding Flashcards
A chemical bond between metals and non-metals where electrons are transferred from the metal to the non-metal to form 2 oppositely charged ions that form electrostatic forces between them
properties of ionic bonidng
3.1 Ionic bonding
- always solid at room temp
- high melting and boiling points
- conduct when molten as ions free to carry a charge
- brittle and shatter easily
Covalent bonding
3.2 Nature of covalent and dative covalent bonds
A chemical bond between non-metal atoms where a pair of electrons is shared
properties of covalent bonding
3.2 Nature of covalent and dative covalent bonds
- form molecules
- have weak attraction so do not need much energy to overcome this attraction
- gases at room temp
- bonding is betwen atoms
- no charged particles
co-ordinate bonding
3.2 Nature of covalent and dative covalent bonds
Where both electrons come from one of the atoms in a covalent bond
- has the same peroperties as a normal covalent bond
metalic bonding
3.3 Metallic bonding
A chemical bond between metals where outer electrons are delocalised within the lattice of metal ions
- greater the charge greater the attraction
- ‘sea of delocalised electrons’
properties of metalic bonds
3.3 Metallic bonding
- good conductors of electrict due to delocalised electrons that can carry a charge
- good heat conductors due to ions constantly vibrating
- metals are maleable and ductile (made into thin wires) after a distortion the metals will retail their shape is they remain in the same environment
- high melting and boiling points due to giant lattice structures and strong attraction between ions and electrons
- durable depends on size of ion andcharge of ion as there is no individual bonds to break
3.4 Bonding and physical properties
Electronegativity
3.6 Bond polarity
The power of an atom to attract the electron density in a covalent bond towards itself
Electronegativity depends on:
3.6 Bond polarity
1 the nuclear charge
2 the distance between the nucleus and the outer shell electrons
3 the shielding of the nuclear charge by electrons in inner shells.
therefore smaller atoms are more electronegative FONCL
trends in electronegativity
3.6 Bond polarity
- Going up a group in the Periodic Table, electronegativity increases
(the atoms get smaller) and there is less shielding by electrons in inner
shells. - Going across a period in the Periodic Table, the elcctronegativity
increases. The nuclear charge increases, the number of inner main
levels remain the same and the atoms become smaller.
Polarity
3.6 Bond polarity
The unequal sharing of the electrons between atoms in a covalent bond
polar molecules
3.6 Bond polarity
Describes a molecule where the charge is not equally distributed, one end is more positive, the other more negative
van der Waals forces
3.7 Forces between molecules
An intermolecular force between all atoms and molecules caused by temporary dipoles which form very weak electrostatic attractions
Dipole-dipole forces
3.7 Forces between molecules
An intermolecular force between two molecules with permanent dipoles
explain how dipole-dipole forces arise between atoms
3.7 Forces between molecules
- Dipole-dipole forces act between molecules that have permanent
dipoles. - For example, in the hydrogen chloride molecule, chlorine
is more electronegative than hydrogen. - So the electrons are pulled towards the chlorine atom rather than the hydrogen atom.
properties of dipole-dipole
3.7 Forces between molecules
greater the polarity
greater the strength of the dipole
melting point
++ as dipole gets stronger
boiling point
++ as dipole gets stronger
viscosity
++ as dipole gets stronger
density
++ as dipole gets stronger
solubility
polar dissolves in polar, non- polar in non- polar
heat of vaporization
++ as dipole gets stronger
Hydrogen bonding
3.7 Forces between molecules
An intermolecular force between a slightly positive hydrogen atom and a much more electronegative atom which forms a strong interaction
Electron pair repulsion theory
3.5 Shapes of simple molecules and ions
Suggests that the electrons surrounding the central atom in the atoms repel each other, therefore the atoms form a shape where they are furthest away from each other
lone pairs reduce angle by 2.5
bonding pairs repel eachother equally
lone pairs
3.5 Shapes of simple molecules and ions
- A pair of electrons in the outer shell of an electron that isn’t involved in a bond
- reduce bong angle by 2.5
- have stronger repulsion
linear
3.5 Shapes of simple molecules and ions
- 180
- 2 bonding pairs
- eg CO2
trigonal planar
3.5 Shapes of simple molecules and ions
- 3 pairs
- 120
- eg BF3
tetrahedral
3.5 Shapes of simple molecules and ions
- 109.5
- 4 pairs of electrons
- CH4
trigonal pryamidal
3.5 Shapes of simple molecules and ions
- 4 pairs of electrons
- 1 lone pair
- 107
- eg NH3
bent or v-shaped
3.5 Shapes of simple molecules and ions
- 2 bonding
- 2 lone pairs
- 104.5
- eg H2O
trigonal byprimidal
3.5 Shapes of simple molecules and ions
- 5 bonding pairs
- 120 between 3
- 90
-eg PCl5
Octahedral
3.5 Shapes of simple molecules and ions
- 6 bonding pairs
- 90 between all bonds
- eg SF6
