Bonding 3 Flashcards
Positive and negative ions are formed
Ionic
Ionic lattice
Electrostatic forces between oppositely charged ions.
Two non-metals
Covalent
Share their electrons
Covalent
Dative covalent bonding
Atom that accepts the electron pair is an atom that doesn’t have a filled outer main shell ( electron-deficient)
Atom that is donating the electron has a pair of electrons (lone pair)
(contains a shared pair of electrons with both electrons supplied by one atom)
Delocalised electrons
Metallic bonding
Good conductors of heat and electricity
- sea of delocalised electron
- high thermal conductivities
Strength of metals
- charge of ions
- size of ion
Malleable and ductile
Layers can slide over each other
High melting point
Giant structure
Strong attraction between metal ions and sea of delocalised electrons
Electronegativity
The power of an atom to attract the electron density in a covalent bond towards itself
(Electronegativity as the power of an atom to attract the pair of electrons in a covalent bond)
What element is the most electronegative?
Fluorine
Metal and non-metal
Ionic
Polar
Greater the difference in electronegativity the more polar the bond is
Metallic bonding
(Metallic bonding involves attraction between delocalised electrons and positive ions arranged in a lattice)
Positive metal ion and an electron
Sea of delocalised electrons
Ions ( and electrons) repel each other
Good conductor of heat and electricity
Strength
Increase charge of the ion
Malleable and ductile ( layers slide over each other)
High melting point
Ionic bonding
Electrostatic attraction between oppositely charged ions ( creates a ion lattice )
Giant structures - high melting point
Conduct electricity
Brittle and shatter ( small displacement causes two positive ions ( or electrons) to touch each other and repel each other
Covalent bonding
Pair of electrons are shared
Strong covalent bonds are only between the atoms with in the molecule
Weak attraction between molecules so not much energy is needed
Poor conductor
Co-ordinate bonding
Covalent bonding in which both the electrons in the bond come from one of the atoms in the bond
One of the atoms would have a lone pair
Represented by an arrow
Electronegatively increases across a period
Increased nuclear charge
Amount of shielding stays the same
Atoms are smaller because the positive charge makes in smaller
Electronegatively decrease down a group
More distance from the nucleus
Amount of shielding increases
Nuclear charge increases but is counteracted by the shielding effect and distance
Van der waals
At any time the electrons can be anywhere. At any moment it could have a dipole at any time
Closer together the molecules the stronger the force
Larger molecules have larger electron clouds meaning stronger van der waal force
Dipole-dipole
Permeant dipole ( one is positives and one is negative)
Opposite charges attract and repel each other
Hydrogen bonding
Fluorine
Oxygen
Nitrogen
Very electronegative
Importance of hydrogen bonding
Molecules are slightly less closely packed than a liquid so it is less dense than water
Forms on top of ponds
Insulates ponds
Ironing
Ironing provides heat to break hydrogen bonds in the crumpled material and pressure to force the molecules into a new postion
DNA
Stores and copies genetic information that makes offspring like the parents (double-stranded helix) —- two stands are held together by hydrogen bonding
When the cells divid (replicate) the hydrogen bond break. You get a copy of the original helix
Enthalpy change
A measure of heat energy given out or taken in when a chemical or physical change would occur at constant pressure
Enthalpy change of melting
Amount of energy needed to weaken the forces that act between the particles
Per moles
Enthalpy change of vaporisation
Amount of energy to break all the intermolecular bonds between molecular
Per mole
Ionic crystals
NaCl
Strong electrostatic attraction between oppositely charged ions
Melting point 801 c
Metallic crystals
Mg
Lattice has a high melting point
Molecular crystals
Iodine
Held in regular array by intermolecular forces
114 C
Large number of electrons
(Soft/easy to break , low melting point, doesn’t conduct electricity)
Macromolecular crystals
Covalent bonds
String bonds
High melting point
Diamond
Bonds spread through the structure 4 carbon bonds (bond angle = 109.5)
Very hard material
High melting point 3700k+
No electrical charge
Graphite
3 Strong covalent bonds
Weak van der waal forces between 1 pair of electrons ( bond angle = 120)
Two dimensional layer of linked hexagon of carbon atoms
(Spare ) electron in the p-orbital -delocalised electron
High melting temperature
Conducts electricity
Electronegatively depends on
Nuclear charge
Distance between the nucleus and outer shell electrons
Shielding
sulfate
SO4
charge of -2
hydroxide
OH-
nitrate
NO3-
carbonate
CO3 -2
ammonium
NH4+
drawing bonds
covalent bond using a line
co-ordinate bond using an arrow
ice
Ice is a good example of a hydrogen bonded solid.
2 pair of lone electrons
Lone pair–lone pair repulsion is greater than lone pair–bond pair repulsion, which is greater than bond pair–bond pair repulsion
how do electrons arrange themselves?
Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repulsion
how polar bonds form
The electron distribution in a covalent bond between elements with different electronegativities will be unsymmetrical. This produces a polar covalent bond, and may cause a molecule to have a permanent dipole
