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24 Cards in this Set
- Front
- Back
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What is a Covalent Bond? |
A strong attraction between a shared pair of electrons and the nuclei of the two atoms involved in the bond. |
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When does Covalent Bonding occur? |
Covalent Bonding occurs in: Non-metallic elements Compounds formed between non-metals |
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What does Covalent Bonding involve? |
A Covalent Bond involves: The sharing of pairs of electrons between 2 atoms. |
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What is a single covalent bond? |
The sharing of 1 pair of electrons between two atoms |
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What is a double covalent bond? |
The sharing of 2 pairs of electrons between two atoms |
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What is a triple covalent bond? |
The sharing of 3 pairs of electrons between two atoms. |
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Why do atoms want to make covalent bonds? |
When elements, aside the noble gases, take part in chemical reactions they try to: Make their outer shells full in order to achieve stability |
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What are the two types of covalently bonded structures? |
1. Simple Molecular Structures 2. Giant Covalent Structures |
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Why are simple molecular strucutres not Giant? |
Because the molecules contain a fixed number of atoms joined by strong covalent bonds. |
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What holds the molecules together in a simple molecular structure/ substance? |
Weak forces of attraction between molecules AKA: Intermolecular forces of attraction |
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What are the properties of simple molecular compounds? |
1. Low melting and boiling points 2. Don't conduct electricity 3.Usually insoluble in water 4.Usually soluble in non-polar solvents |
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Why do simple molecular structures have low melting/boiling points? |
Because their: weak intermolecular forces of attraction require little energy to overcome |
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Why are Giant Covalent structures always elements? |
Because there are no molecules. Every atom is covalently bonded to its neighbors Infinite num. of atoms |
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What are the properties of Giant Covalent Compounds? |
1. Extremely high melting and boiling points 2. Insoluble in all solvents 3. 'Variable' conductivity |
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What are some common examples of giant covalent structures? |
Allotropes of carbon aside Buckminster fullerenes. 1. Diamond 2. Graphite |
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Why do giant covalent structures have extremely high melting and boiling points? |
Because : Lots of incredibly strong covalent bonds must be broken. Requires lots of energy |
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What are the physical properties of Diamond? (Giant Covalent Structure) |
-Extremely hard (used in cutting tools) -V. high melting point -Insoluble in all solvents -Doesn't conduct electricity |
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Why is diamond extremely hard? |
Because each carbon atom is bonded to 4 others in a tetrahedral arrangement. This forms 4 single covalent bonds. |
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Why does diamond have a V. high melting point? |
Because: Many incredibly strong covalent bonds must be broken This requires lots of energy |
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Why does diamond not conduct electricity? |
Because: It has no moving charged particles (all outer shell electrons are bonding) |
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What are the physical properties of Graphite? |
- Soft (used as lubricant) -V. high melting point -Insoluble in all solvents -Conducts electricity |
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Why is Graphite 'soft'? |
Because: Carbon atoms are covalently bonded to 3 others. Forms layers of fused hexagons with weak forces of attraction that can slide over each other. |
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Why does Graphite have a V. high melting point? |
Because: Many V. strong covalent bonds must be broken This requires lots of energy |
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Why can Graphite conduct electricity? |
Because: Each C uses 3 electrons bonding. 4th electron in outer shell can move through layer -Delocalised electrons |
