Bonding Flashcards
What is ionic bonding
Electrostatic forces of attraction between oppositely charged ions in a lattice
Properties of ionic compounds
Solid at room temperature, giant lattice structure, conducts electricity when molten or dissolved, brittle
What is covalent bonding
A bond containing a shared pair of electron
What is a dative covalent bond
When the shared pair of electrons in a bond are supplied from one atom only
How is a dative covalent bond depicted
Using an arrow
Properties of covalent molecules
Low melting points due to the weak intermolecular forces of attraction, poor conductors of electricity
What is metallic bonding
Attraction between delocalised electrons and positive ions arranged in a lattice
What does the strength of a metal depend upon
Charge of the ion (more electrons in sea, stronger attraction) and size of the ion (nucleus closer to sea, stronger attraction)
Properties of metals
Good conductors of heat and electricity, malleable and ductile, high melting point, giant lattice
What is electronegativity
The power of an atom to attract the pair of electrons in a covalent bond towards itself
What does electronegativity depend upon
Nuclear charge, distance between the nucleus and outer electrons, shielding
Trend of electronegativity down a group
Less electronegative as larger distance from nucleus, more shielding, same nuclear charge
Trend of electronegativity across a period
More electronegative as larger nuclear charge, same distance from nucleus, same shielding
What occurs with electronegativity in a covalent bond
If there is a difference in electronegativity, this will produce a polar covalent bond. If the difference is too large, it will become a permanent dipole
The greater the difference in electronegativity…
The more polar is the covalent bond
What are the three intermolecular forces
Van der Waals forces, dipole-dipole forces and hydrogen bonding
What are Van der Waals forces
The electrons at one instant may tend to be further on one side than the other, this creates a dipole causing other atoms to have the same
What do Van der Waals affect
All atoms at all times
What are dipole-dipole forces
When a molecule has a dipole bond, which attracts each other. If the dipoles are symmetrical they can cancel each other
What is hydrogen bonding
Stronge intermolecular force between a bond hydrogen bond with a heavily positive charge attracted to another atom, with a heavily negative charge, with a lone pair
Explain hydrogen bonding in ice
Water has hydrogen bond and when it freezes, the hydrogen bonds form and create a diamond-like structure. This has a lower density, causing ice to float on water, enabling fish to survive in winter
What are the types of crystal structures
Ionic, metallic, macromolecular and molecular
What are crystals
Crystals are solids with a regular arrangement of particles
Describe ionic crystals with example
Strong electrostatic forces of attraction between oppositely charged ions such as sodium chloride. Attractions extend through the whole structure
Describe metallic crystals with example
Attraction between lattice of positive ions and sea of delocalised electrons such as magnesium
Describe molecular crystals
Intermolecular forces holding the covalent molecules together such as iodine. Large number of electrons so Van der Waals are strong enough to produce a solid crystal. But soft.
Describe diamond
Macromolecular - covalent bonds between carbon atoms in 4 directions. Creating tetrahedral shape of 109.5 degrees. High melting point
Describe graphite
Macromolecular - covalent bonds between carbon atoms in 3 directions. Shape of trigonal planar. Delocalised electrons. Weak intermolecular forces between layers. Conducts electricity but soft material
How to draw hydrogen bonding
Dashed line, all charges, all lone pairs, 3 bonded atoms must be in a straight line, bond from lone pair to delta +
What are the three elements that are electronegative enough to produce hydrogen bonding
Nitrogen, oxygen, fluorine
Explain how dipole-dipole forces arise in hydrogen chloride
Difference in electronegativity produces a polarity, slightly negative charge from chlorine attracts the slightly positive charge from another hydrogen
