Chemical Bonding Flashcards

1
Q

definition of an ionic bond?

A

the strong electrostatic forces of attraction between oppositely charged ions in a giant ionic lattice

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2
Q

why do atoms form ionic bonds?

A

to obtain a stable noble gas configuration

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3
Q

why do ionic compounds arrange themselves in a lattice structure?

A
  • alternating cations and anions
  • maximize attraction between oppositely charged ions
  • minimize repulsion between similarly charged ions
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4
Q

how is the strength of an ionic bond determined?

A
  • the greater the charge, the stronger the bond
  • the smaller the ionic radius, the stronger the bond
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5
Q

properties of an ionic compound?

A
  • high b.p. and m.p.
  • can conduct electricity when aqueous
  • cannot conduct electricity when solid
  • hard
  • brittle
  • generally soluble in water
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6
Q

why do ionic compounds have a high b.p., m.p. and are hard?

A

oppositely charged ions are held by strong electrostatic forces of energy that require a large amount of energy to overcome

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7
Q

why can an aqueous ionic compound conduct electricity?

A
  • presence of free mobile ions
  • mobile charge carriers to conduct electricity
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8
Q

why can’t a solid ionic compound conduct electricity?

A
  • ions vibrate about fixed positions
  • absence of free mobile ions or delocalised electrons
  • no mobile charge carriers to conduct electricity
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9
Q

why are solid ionic compounds brittle?

A
  • sliding of ion layers
  • similarly charged ions meet and repel one another
  • resultant repulsion shatters the structure
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10
Q

how are metallic bonds formed?

A
  • metals lose valence electrons to form cations
  • valence electrons are delocalised
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11
Q

definition of a metallic bond?

A

strong electrostatic forces of attraction between the metal cations and sea of delocalised electrons in a giant metallic lattice structure

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12
Q

how is the strength of a metallic bond determined?

A
  • the more valence electrons contributed to the sea of delocalised electrons, the stronger the bond
  • the smaller the metallic radius, the stronger the bond
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13
Q

properties of metals?

A
  • high b.p. and m.p.
  • good conductor of electricity
  • good conductor of heat
  • malleable
  • ductile
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14
Q

why do metals have a high b.p. and m.p.?

A

large amounts of energy is required to overcome the strong electrostatic forces of energy between the metal cations and sea of delocalised electrons

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15
Q

why are metals good conductors of electricity?

A
  • presence of delocalised electrons
  • mobile charge carriers to conduct electricity
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16
Q

why are metals good conductors of heat?

A
  • kinetic energy of electrons at heated end increases
  • energy transferred to the rest of the metal through delocalised electrons
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17
Q

why are metals malleable?

A

layers of atoms can slide over one another without breaking the metallic bond

18
Q

why are metals ductile?

A
  • metallic bonds are easily reformed
  • giant metallic lattice is easily restored
19
Q

what are alloys?

A

a mixture of a metal another element

20
Q

why are alloys stronger and harder than pure metals?

A
  • insertion of differently sized atom
  • regular arrangement of atoms disrupted
  • irregularity in the metal structure
  • layers of atoms cannot slide over one another
21
Q

how are covalent bonds formed?

A

sharing electrons between atoms to form a molecule, achieving a stable octet or duplet configuration

22
Q

definition of covalent bonds?

A

electrostatic forces of attraction between the shared pair of electrons and positively charged nuclei of both atoms in the bond

23
Q

how to determine the strength of the covalent bond?

A
  • the more effective the orbital overlap (smaller atomic radius), the stronger the bond
  • the shorter the bond length, the stronger the bond
  • the greater the bond energy, the stronger the bond
24
Q

what are the big 4?
(giant molecular structure)

A
  1. diamond
  2. graphite
  3. silicon
  4. silicon dioxide
25
Q

structure of diamond and silicon?

A

giant molecular structure where each carbon/silicon atom is bonded to four other atoms by numerous strong covalent bonds in a tetrahedral arrangement

26
Q

structure of silicon dioxide?

A

giant molecular structure where each silicon atom is bonded to four oxygen atoms and each oxygen atom is bonded to two silicon atoms by numerous strong covalent bonds

27
Q

definition of an allotrope?

A

different forms of the same element with similar chemical properties but different physical properties

28
Q

properties of silicon, silicon dioxide and diamond?

A
  • high m.p and b.p.
  • hard
  • cannot conduct electricity
  • insoluble in water
29
Q

why are silicon, silicon dioxide and diamond hard and have a high b.p. and m.p.?

A

very large amounts of energy required to overcome the numerous strong covalent bonds between atoms in the giant molecular structure

30
Q

why are silicon, silicon dioxide and diamond not conductors of electricity?

A
  • all electrons used for bonding
  • no free mobile ions and delocalised electrons
  • absence of mobile charge carriers to conduct electricity
30
Q

properties of graphite?

A
  • can conduct electricity parallel to layers but not perpendicularly
  • soft
  • slippery
  • insoluble in water
31
Q

structure of graphite?

A
  • hexagonal flat parallel layers
  • each carbon atom covalently bonded to three other atoms
  • adjacent layers held by weak intermolecular forces
32
Q

why can graphite conduct electricity parallel to layers but not perpendicularly?

A
  • fourth non-bonding electron is delocalised over the whole layer
  • mobile charge carriers to conduct electricity
33
Q

why is graphite soft and slippery?

A
  • adjacent layers held by weak intermolecular forces
  • easily overcome
  • layers slide over one another
34
Q

difference between intermolecular forces of attraction and covalent bonds?

A
  • covalent bonds are stronger and bond atoms to form compounds
  • intermolecular forces of attraction are weaker and bond molecules
35
Q

properties of simple molecular substances?

A
  • low m.p. and b.p.
  • cannot conduct electricity
  • mostly not soluble in water
36
Q

why do simple molecular substances have a low m.p. and b.p.?

A

low amounts of energy required to overcome the weak intermolecular forces of attraction between molecules

37
Q

why can’t simple molecular substances conduct electricity?

A
  • no free mobile ions and delocalised electrons
  • absence of mobile charge carriers to conduct electricity
38
Q

elements that are involved in hydrogen bonding (a type of intermolecular force of attraction) other than hydrogen?

A
  1. nitrogen
  2. oxygen
  3. fluorine
    (aka. NOF)
39
Q

general rank in strength for different bonds?

A
  1. ionic/metallic/covalent bond
  2. hydrogen bond
  3. intermolecular forces of attraction