Bonding

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Define ionic bonding
When positive and negative ions are held together by electrostatic attraction
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What form do most ionic substances take and describe it
Giant lattice structure, which is the same basic unit repeated in a regular structure
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When can an ionic substance conduct electricity?
When it is molten or dissolved as the ions are free to move and carry a charge
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Why do ionic substances have high melting points ?
Lattices are held together by lots of strong electrostatic forces which need a lot of energy to break
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What property of water allows it to dissolve ionic substances?
Water is a dipolar molecule
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Define covalent bonding
Two atoms share e- to fill both outer shells & held together electrostatically
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What is a giant covalent structure ?
Huge networks of covalently bonded atoms
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Whats another term for giant covalent?
Macromolecular
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Name an element that forms two giant covalent substances and name these structures
Carbon & graphite + diamond
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Name the three properties of graphite
Weak layers, free delocalised electrons and low density
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Why is diamond the hardest substance in the world?
Each carbon atom is covalently bonded to four other carbon atoms in a tetrahedal shape
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Name three properties of diamond
Extremely hard so used for tools, vibrates easily so used as a thermal conductor & it cannot conduct electricity
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Define coordinate bonding
When an atom donates a pair of electrons to a central atom, represented by an arrow
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Describe electron repulsion theory
Electrons are negatively charged so electron pairs repel each other, pairs form far away from each other as possible & this determines the shape
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What is the difference between wedge and broken line notation
Wedges show bonds that are protruded and broken lines show bonds that go inwards
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Name the three things you need to know to determine shape
Central atom, number of bonding pairs & number of lone pairs
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Define electronegativity
An atom's ability to attract the electron pair in a covalent bond
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What is the most electronegative element
Fluorine - 4 on the Pauling Scale
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What makes a bond polar?
In a covalent bond between two atoms of different electronegativities, the bonding electron will be pulled towards the more electronegative atom
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What determines the strength of polarity?
The greater the difference in electronegativity between the atoms, the more polar the bond
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What type of intermolecular force do polar molecules have?
Permanent dipole-dipole
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What is an intermolecular force?
Forces between molecules
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What intermolecular force is found between all atoms and molecules?
Van der Waals
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Explain how van der waals are formed?
Electrons move quickly and are likely to build up in one part of an atom, causing a temporary dipole. This dipole causes another dipole on a neighbouring atom and each atom then has a dipole in a domino effect
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Why do van der waals prefer unbranched molecules?
Long straight molecules can lie close, the closer the molecules the stronger the forces
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What properties do molecules with lots of van der waals have?
Large electron clouds, stronger molecules and higher boiling/melting points
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What is the strongest intermolecular force and why?
Hydrogen bonding as it contains very electronegative elements making it very polar
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What three elements does hydrogen form hydrogen bonds with?
Fluorine, nitrogen and oxygen
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What is metallic bonding?
Positive metal ions are attracted to the delocalised negative electrons, forming a lattice of closely packed cations in a sea of delocalised electrons
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Why do metals have high melting and boiling points?
Because of the strong electrostatic attraction between the cations and the delocalised sea of electrons
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What makes metals good thermal and electrical conductors?
Their ability to pass kinetic energy and to carry a current due to their delocalised electrons
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Why are simple covalent compounds easier to melt than giant covalent substances?
To melt a simple structure you just have to break its intermolecular forces only but for giant structures the covalent bonds have to be broken too
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Other cards in this set

Card 2

Front

What form do most ionic substances take and describe it

Back

Giant lattice structure, which is the same basic unit repeated in a regular structure

Card 3

Front

When can an ionic substance conduct electricity?

Back

Preview of the front of card 3

Card 4

Front

Why do ionic substances have high melting points ?

Back

Preview of the front of card 4

Card 5

Front

What property of water allows it to dissolve ionic substances?

Back

Preview of the front of card 5
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