Ionic and Covalent Bonding

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  • Created by: Lotto65
  • Created on: 22-01-17 13:30
What are atoms trying to achieve when combining with other atoms?
Noble gas configuration
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How are ionic compounds formed?
When electrons are transferred from one atom to another to form ions with complete outer shells of electrons
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What attracts positive and negative ions to each other in an ionic compound?
Electrostatic forces of attraction
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Are electrostatic forces strong or weak?
Strong
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What sort of structure do ionic compounds form?
A strong 3D lattice with a repeating pattern of positive and negative ions
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Do ionic compounds have low or high melting points? Why?
High because lots of energy is required to overcome the strong electrostatic forces of attraction and the strong lattice
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Give an example of an ionic compound
Sodium chloride NaCl
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How is sodium chloride formed?
When sodium burns in chlorine gas
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How is chlorine normally found?
A covalently bonded diatomic molecule
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When chlorine is naturally found, does it already have a noble gas configuration?
Yes
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How can sodium bond to an atom that already has a noble gas configuration and is bonded to something else?
The energy released when the ionic lattice is formed is enough to break the bond in the chlorine molecule to create individual molecules of chlorine
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What does the charge of an ion depend on?
How many electrons the atom gained or lost to get a full outer shell
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Which elements can form different types of ion? Give examples
Transition metals e.g. Fe2+ and Fe3+ and Cu+ and Cu2+
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The overall charge of an ionic compound must be...
Zero
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What is the formula of calcium phosphide?
Ca3P2
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What is the formula of aluminium bromide?
AlBr3
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When writing the formulae of ionic compounds, do you need to write the charges of each element?
No
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What is a polyatomic ion?
Ions containing more than one element
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What happens to the charge in polyatomic ions?
Spread across whole ion
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Why are negative ions sometimes called acid radicals?
They are formed when an acid loses one or more H+ ions
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What do brackets mean in a formula?
The subscript covers all elements in that ion
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What are ionic compounds composed of?
A metal and a non-metal or a cation and an anion
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In terms of electronegativity, what are ionic compounds composed of?
Elements in group 1,2,3 with a low electronegativity and elements with a high electronegativity in groups 15,16,17
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What does the difference in electronegativity need to be for ionic bonding to occur?
1.8+
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What sort of lattice is formed in solid ionic compounds?
Crystal lattice
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What is the ionic bond in a lattice?
The sum of all the electrostatic attractions and repulsions in the lattice
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Why are many ionic compounds soluble in water?
The hydration energy of the ions provides enough energy to overcome the lattice enthalpy
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Why can solid ionic compounds not conduct electricity?
The ions are held in fixed positions
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Why can molten ions conduct electricity?
The ions are free to move and so are chemically decomposed at electrodes
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What does covalent bonding involve?
The sharing of pairs of electrons so each atom in a molecule achieves noble gas configuration
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What is the simplest covalent molecule?
Hydrogen
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How do covalent bonds form?
Atoms share electrons which are electrostatically attracted to the other positive nucleus. This forms a directional bond between two atoms
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What are directional bonds?
Bonding where the atoms prefer a particular orientation/ direction in space
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Give an example of another diatomic molecule with a single covalent bond
Chlorine
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1 pair of electrons = ...
1 bond
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What is shown in a Lewis dot cross diagram?
Just the valence electrons
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Is this a Lewis dot cross diagram F-F? Why/ why not?
No because it does not show the valence electrons, only the bond formed
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How many single bonds does Nitrogen form with Hydrogen in Ammonia? How many lone pairs are there?
3 single bonds, one lone pair
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Give some examples of compounds which share multiple electron pairs
O=O, O=C=O, CH2CH2
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What is a coordinate covalent bond?
When the electrons in the shared pair come from the same atom
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How do you show coordinate covalent bonds on a diagram?
With an arrow -->
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What are the different ways of bonding in sulfur dioxide or sulfur trioxide?
A coordinate bond between sulfur and oxygen or double bonds between the sulfur and oxygen
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In diatomic molecules, how will the electron pairs be shared? Why?
Equally because both atoms exert identical attraction
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What happens to the attraction of the bonding pair when the atoms are different elements?
The more electronegative atom exerts greater attraction for the electron pair
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What does it mean if you have a polar bond?
One end is more electron rich than the other
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The bigger the difference in electronegativity between elements..
The more polar the bond
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What is the name of group 16?
The chalcogen group
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What is the octet rule?
The rule that electrons can be lost, gained or shared to acquire the noble gas core electron configuration
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The greater the charges in an ionic compound...
The greater the melting point
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What is Coulomb's law of electrostatics?
Electrostatic force is directly proportional to interacting charges and inversely proportional to the square of the distance between them
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What is volatility?
The tendency for a substance to vaporise
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Are ionic compounds volatile? Why/why not?
No because they have strong electrostatic forces of attraction
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Ionic compounds dissolve in ... solvents
Polar
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Would ionic compounds dissolve in hexane? Why/ why not?
No because it is a non-polar solvent
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How does dissolving occur in ionic compounds?
The positive hydrogen charges in water are attracted to the anions and the negative charges in water are attracted to cations. Individual ions are pulled out of the lattice and are surrounded by water molecules
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What are some uses of ionic liquids?
Solvents, electrolytes in electric power sources and green industrial processes
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The stronger the bond...
The shorter the bond
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What must the electronegativity sum be for a pure covalent bond?
0
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What must the electronegativity be for a polar covalent bond?
0
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Why do microwaves increase the temperature of food?
Water is a dipole molecule but when coming into contact with microwaves, it constantly changes its orientation to align with alternating electromagnetic field. The flipping and rotation of water molecules causes heat dissipation and heating up
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Other cards in this set

Card 2

Front

How are ionic compounds formed?

Back

When electrons are transferred from one atom to another to form ions with complete outer shells of electrons

Card 3

Front

What attracts positive and negative ions to each other in an ionic compound?

Back

Preview of the front of card 3

Card 4

Front

Are electrostatic forces strong or weak?

Back

Preview of the front of card 4

Card 5

Front

What sort of structure do ionic compounds form?

Back

Preview of the front of card 5
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