3.0 Bonding Flashcards
Explain how and why a magnesium atoms forms a positive ion
Magnesium has 2 electron in its outer main energy level. he loss of these two negative electrons increase stability and leaves 2 more protons than electrons in the atomic structure, leaving it with a 2+ charge
Explain how and why a chlorine atom forms a negative ion
Chlorine has 7 electrons in its outer main energy level. The gain of 1 electron stabilises the molecule and leaves 1 more electron than proton in the atomic structure, giving the ion a 1- charge
Why do bonds form between ions?
Oppositely charged ions form an electrostatic attraction
What is an ionic lattice?
A series of electrostatic attractions between oppositely charged ions, acting in all directions, with a specific ratio of positive to negative ions
How do you find the formula of an ionic compound?
the simplest ratio of ions in a lattice
Give the formulae of these common compound ions; sulfate, hydroxide, nitrate, carbonate, and ammonium
SO42-
OH-
NO3-
CO32-
NH4+
What factors affect the strength of an ionic bond?
Size of charge
Ionic radius
Describe a single covalent bond
A shared pair of electrons
Describe a double and triple covalent bond
Two shared pairs of electrons
Three shared pairs of electrons
Describe a co-ordinate bond
A shared pair of electrons where both electrons are supplied by one atom
What type of bond is described by;
A single line
A single arrow
Covalent bond
Co-ordinate bond
Describe the bonding on a metal
Electrostatic attraction between delocalised electrons and positive ions arranged in a lattice
What affects the strength of a metallic bond?
The charge on the metal ions
The number of delocalised electrons
Name the four types of solid crystal structure sand give an example of each
Ionic = Sodium chloride
Metallic = Magnesium
Molecular = ice/iodine
Macromolecular = graphite/diamond
What are the properties of ionic crystals?
high mpt/bpt, conducts electricity when molten or dissolved as ions can flow through and form a current
What are the properties of metallic crystals?
high mpt/bpt, malleable, ductile as rows of ions can easily slide over in layers, conducts electricity and heat due to delocalised electrons.
What are the properties of molecular crystals?
Low mpt/bpt as weak intermolecular forces are easily overcame, brittle, do not conduct due to no charged ions/ delocalised electrons
What are the properties of graphite?
Soft as layers of atoms slide over, conducts electricity as delocalised electrons can flow, high mpt/bpt as 3 strong covalent bonds to break
What are the properties of diamond?
Hard, high mpt/bpt as lots of energy to break bonds, does not conduct electricity as no delocalised electrons to flow but can conduct heat
Why do molecules form specific shapes around a central atom?
Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repulsion
List the key molecule shapes including bond angles
Linear = 180
Bent = 105
Trigonal planar = 120
Square planar = 90
Trigonal pyramid = 107
Tetrahedral = 109.5
Trigonal bypryamid = 120/90
Octahedral = 90
What are the steps in predicting the shape of a molecule?
- Number of outer electrons around central atom
- Add number of covalent bonds made with central atom
- Total/2 = electron pairs
- Find number of bond pairs and lone pairs
- Pairs of electrons repel as far as possible
Define electronegativity
The ability of an atom to pull a bonding pair of electrons towards itself within a covalent bond
What causes a covalent bond to be polar?
Difference in electronegativity between the atoms
