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50 Cards in this Set
- Front
- Back
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Chemical bonds |
Binding force between particles that results in lower energy arrangements |
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Valence Shells |
Shell that is furthest away from nucleus |
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Valence electrons |
Found in outermost shell ; Only electrons involved in bonding |
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What kind of configuration does Helium have? |
A duplet configuration |
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What kind of configuration do all other noble gases have |
An octet configuration |
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When can an atom be stable |
When it has a duplet or octet config. |
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What do atoms have to do in order to achieve a noble gas config.? |
Donate, accept or share electrons |
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What is ionic bonding? |
Electrostatic attraction between oppositely charged ions |
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How is the ionic bond formed? |
When one or more electrons are transferred from the valence shell of one atom to the valence shell of another ; cations and anions formed usually have a stable noble gas config. ; cations and anions attract each other by electrostatic attraction , which holds these oppositely charged particles together |
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Why are atoms electrically neutral? |
They have the same number of protons and electrons |
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Which ones gain/lose electrons to obtain noble gas config? |
Metals tend to lose electrons (+) Non-metals tend to gain electrons (-) |
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What are TWO compounds that form ionic bonds? |
Sodium chloride (NaCl) and Magnesium Oxide |
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What is the nature of ionic bonds? |
Strong ; non-directional as there is no specific attraction of the ion in any particular direction |
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What is the structure of ionic compounds? |
Exists as a giant lattice structure consisting of oppositely charged ions attracted to each other by ionic bonds |
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What is repeated throughout the structure? |
The regular arrangement of ions |
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Why are the ions arranged in a lattice? |
Attraction between the oppositely charged ions is at a maximum and the repulsion of similarly charged ions is at a minimum |
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What are the four properties of ionic compounds? |
High melting and boiling points ; Hard but brittle ; Non-conductors of electricity in solids but good electrical conductors in liquid or aqueous solution ; Usually soluble in water except in organic solvents such as ethanol |
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Why do ionic compounds have high melting and boiling points? |
A large amount of energy is required to overcome the strong electrostatic forces between oppositely charged ions in the giant ionic lattice structure during a change in physical state |
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Why are ionic compounds hard and brittle? |
Hard because compounds are strong and non-directional ; Brittle because the ordered arrangement of oppositely charged ions in the giant lattice can be easily dislocated when applied a sheer amount of stress |
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How does this happen? |
Sheer stress causes dislocation of the lattice, which causes similarly charged ions to be close together. This results in repulsion and causes a fracture in the giant lattice structure. |
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Why are ionic compounds non-electrical conductors in solid state? |
This is because the ions are held in a fixed position by strong ionic bonds in the giant lattice structure and are not free to move around |
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Why are ionic compounds good conductors of electricity when molten or dissolved in aqueous solution? |
The lattice is broken down and the ions are free to move around. |
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What is covalent bonding? |
It is the electrostatic attraction between positively charged non-metal atoms and the shared pair of electrons between them. |
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How is the covalent bond formed? |
When non-metal atoms share electrons to form molecules. After bonding, each atom attains noble gas configuration. |
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What is a SINGLE covalent bond? |
When only 1 pair of electrons are shared between 2 atoms. |
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What is the nature of covalent bonds? |
Strong as each pair of shared electrons is attracted by both the bonding nuclei ; directional |
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What is the structure of simple covalent molecules? |
The atoms within each molecule are held together by strong covalent bonds, but the separate molecules are held together by weak intermolecular forces of attraction. |
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What are the intermolecular forces of attraction? |
Weak forces of attraction between simple covalent molecules. These forces are easily broken by heat. |
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What are giant covalent molecules? |
All atoms are bonded by strong covalent bonds to form a giant three-dimensional structure. |
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How is a diamond molecule structured? |
Each carbon atom forms strong covalent bonds with 4 other carbon atoms. The atoms form a tetrahedral arrangement throughout the element. |
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Why is diamond such a hard substance? |
A large amount of energy is required to break the strong covalent bonds between the carbon atoms. |
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Why can't diamond conduct electricity? |
All electrons are bonded and are not free moving, hence they cannot conduct electricity. |
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How is the structure of a graphite molecule like? |
Each carbon in graphite is bonded to 3 other carbon atoms by strong covalent bonds, forming a hexagonal structure. Weak intermolecular forces exist within each layer. |
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What are allotropes? |
Different forms of an element in the same physical state. |
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What are the properties of graphite? |
Graphite is able to conduct electricity and is soft and slippery. |
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Why can graphite conduct electricity? |
Each carbon atom in graphite has 1 valence electron that is not used to form covalent bonds. These DELOCALISED electrons can flow along a layer and conduct electricity. |
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Why is graphite soft and slippery? |
Layers of carbon can slip over one another since the weak intermolecular forces of attraction can be easily broken. |
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Why do simple covalent molecules have low MP and BP? |
Low amount of energy required to overcome the weak intermolecular forces of attraction between the discrete molecules during a change in physical state. |
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Why do giant covalent molecules (macromolecules) have high BP and MP? |
Large amount of energy is required to overcome the strong covalent bonds between the atoms in the giant covalent structure. |
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What are the two other properties of covalent molecules? |
Usually insoluble in water but soluble in organic solvents ; Does not conduct electricity in any state |
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Exceptions of covalent molecules that are soluble? |
Sugar, chlorine, alcohol. |
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Why can't covalent molecules conduct electricity? |
Absence of mobile charge carriers |
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Exceptions? |
Graphite and aqueous acids (acids ionise in water to form ions) |
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What is metallic bonding? |
Electrostatic attraction between a lattice of positive metal ions and a 'sea' of delocalised electrons. |
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How is a metallic bond formed? |
Metals are electropositive in nature, which means that they tend to lose their valence electrons to form positive ions to obtain noble gas configuration. The valence electrons are free to move about, which results in a closely-packed, regular arrangement of positive metals ions surrounded by a 'sea' of delocalised valence electrons |
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What is the nature of a metallic bond? |
Non-directional (no preferred attraction for the delocalised electrons in any particular direction ; strong |
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What is the structure of metals? |
Exists as a giant crystal lattice consisting of positive metal ions and the 'sea' of delocalised electrons attracted together by metallic bonds. |
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What are the physical properties of metals? |
Malleable and ductile ; good conductors of electricity |
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Why are metals malleable and ductile? |
When shear stress is applied, the layers of cations in the lattice can slide over one another without being broken. The structure is still kept intact because the delocalised electrons act as the 'electronic glue' among the layers. |
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Why are metals good conductors of electricity? |
Due to mobility of delocalised electrons within the giant metal lattice. Applied voltage can push the mobile electron cloud through the lattice. |
