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Bonding Flashcards

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1
Q

What is the definition of Ionic bonding?

A

An electrostatic force of attraction between oppositely charged ions

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2
Q

What two factors affect the strength of an ionic bond

A

-ionic radius
-size of charge

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3
Q

As ionic radius increases…

A

Ions become less charge dense so there are weaker ESFA between cations and Cl- ions

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4
Q

Smaller more …… charged ions are more ………, so attract oppositely charged ions more ……….

A

-highly
-charge dense
-strongly

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5
Q

What is the perfect ionic model?

A

-ions are perfectly spherical
- no electron density between them

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6
Q

Ionic radius decreases across the period because…

A

Shielding stays the same but ionic charge increases

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7
Q

What is covalent bonding?

A
  • the electrostatic force of attraction between a shared pair of electrons and two positive nuclei
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8
Q

What do we use to measure the strength of a covalent bond?

A

Bond enthalpy (kJ mol)

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9
Q

The longer the covalent bond…

A

The weaker the bond

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10
Q

Why do covalent bonds get weaker when atomic radius increases?

A

-As atomic radius increases covalent bonds get longer
-Atoms cannot approach as closely so there is a weaker ESFA between the two nuclei and the shared electrons

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11
Q

Multiple covalent bonds are…

A

Shorter and stronger than single bonds.
(Stronger ESFA between 2 nuclei and multiple pairs of electrons)

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12
Q

What is octet expansion?

A

-elements in period 3 and beyond can accommodate up to 18 electrons in their outer shell

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13
Q

What is a dative covalent bond?

A

-one atom supplies both electrons required to form a covalent bond.

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14
Q

What are the two requirements for the formation of a dative covalent bond?

A

-one atom must have a vacant orbital
-another atom must have a lone pair of electrons

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15
Q

A dimer is when…

A

Two of the same molecule join together to form a larger molecule via dative covalent bonding

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16
Q

What is metallic bonding?

A

An electrostatic force of attraction between a positive metal cation and delocalised electrons

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17
Q

What are the factors that affect the strength of a metallic bond?

A

-size of charge
-ionic radius
(Charge denisty)
-# of electrons in the sea

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18
Q

Ionically bonded molecules have a ………. Structure

A

Giant Ionic Lattice

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19
Q

Why do ionic compounds have high melting/boiling points?

A

-strong ESFA between oppositely charged ions that require a lot of energy to overcome

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20
Q

Ionic compounds can only conduct when……………..

A

-molten or dissolved in a solvent
- this is because ions can move and carry charge allowing current to flow

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21
Q

Why can’t ionic compounds conduct when solid?

A

-ions are held in place

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22
Q

Simple molecular structure has ___________ bonding

A

Covalent

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23
Q

Describe simple molecular structure

A

-strong covalent bonds between atoms
-weak intermolecular forces of attraction between molecules

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24
Q

Why is the melting/boiling point of simple molecular structures low?

A

-weak forces of attraction between molecules that are easy to overcome with little energy

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25
Q

Do simple molecular compounds conduct electricity?

A

No

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26
Q

Name three types of compounds with giant covalent lattice structure

A

-Diamond
-Graphite
-Silicon dioxide

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27
Q

Diamond
Each carbon atom is bonded to __ others. Atoms are held in ________ positions by ________________ bonds

A

-4
-fixed
-strong covalent

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28
Q

Describe graphites structure

A

-each carbon atom is bonded to three others
-atoms are arranged in layers
-strong covalent bonds between atoms
-weak forces of attraction between layers means they can slide over each other
-delocalised electrons

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29
Q

Why do compounds with giant covalent lattice have high boiling/melting points?

A

Lots of strong covalent bonds between atoms that require lots of energy to break.

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30
Q

Why can’t diamond conduct electricity but graphite can?

A

-Diamond does not have delocalised electrons while graphite does

31
Q

Some simple molecular _______ are soluble in water

A

-gases
(Ammonia)

32
Q

Giant metallic lattice has a regular…

A

-Close packed arrangement of positive metal ions surrounded by a sea of delocalised electrons.
-layers of ions can slide over each other
- delocalised electrons can move throughout the structure carrying charge

33
Q

Why do metals have high boiling points

A

-strong ESFA between positive metal ions and delocalised electrons that requires a lot of energy to overcome

34
Q

What are the shapes of molecules determined by?

A

-bonding and lone pairs of electrons

35
Q

What is valence shell electron pair repulsion theory?

A

-bonding pairs repel other bonding pairs equally and as much as possible
-lone pairs repel other lone pairs equally and as much as possible
-lone pairs repel more than bonding pairs

36
Q

What is the shape for 2 bonding pairs?

A

Linear

37
Q

What is the shape for 3 bonding pairs?

A

Trigonal planar (120)

38
Q

What is the shape for 2 bonding pairs and one lone pair?

A

Bent (117.5)

39
Q

What is the shape for 4 bonding pairs?

A

Tetrahedral (109.5)

40
Q

What is the shape for 3 bonding pairs and one lone pair?

A

Trigonal pyramidal (107)

41
Q

What is the shape for 2bonding pairs and 2 lone pairs?

A

Bent
(105.5)

42
Q

What is the shape for 5 bonding pairs?

A

Trigonal bipyramidal (90 + 120)

43
Q

What is the shape for 4 bonding pairs and one lone pair?

A

Sawhorse (87.5)

44
Q

What is the shape for 3 bonding pairs and two lone pairs

A

T shaped
(85 + 180)

45
Q

What is the shape for two bonding pairs and three lone pairs?

A

Linear (180)

46
Q

What is the shape for 6 bonding pairs?

A

Octahedral (90)

47
Q

What is the shape for 5 bonding pairs and one lone pair?

A

-Square pyramidal (87.5 _ 90)

48
Q

What is the shape for 4 bonding pairs and 2 lone pairs

A

Square planar (90)

49
Q

What is the shape for 3 lone pairs and 3 bonding pairs?

A

T shaped (87.5)

50
Q

What is the shape for 4 lone pairs and two bonding pairs

A

Linear

51
Q

Name the 4 stages a bond goes through from ionic -> covalent

A

Ionic
Distorted ions
Polarized Covalent bond (has ionic character)
Covalent bond

52
Q

What is electronegativity?

A

The ability of an atom to withdraw electron density towards itself in a covalent bond

53
Q

What are the two factors affecting electronegativity?

A

-Nuclear charge
-Atomic radius
(Small atoms with high nuclear charge are electronegative))

54
Q

How does electronegativity change down a group?

A

-decreases

-down the period atomic radius increases therefore extra energy levels, more shielding, weaker ESFA between nuclear and bond, e negativity decreases

55
Q

What is the most electronegative element?

A

Fluorine

56
Q

What are the requirements of the perfect ionic model?

A

Perfect spherical point charges
-no electron density found between them
-held together by ESFA

57
Q

What are the two deviations from the perfect ionic model?

A

-A polarising cation (small highly charged ions such as Li+ and Al3+)
-A polarisable anion (large diffuse ions (spread out) ) (Br- + I-)

58
Q

Describe one example of how the perfect ionic model falls apart

A

-SIlver polarises the Iodide ion
-distorting the electron cloud

59
Q

What are the three types of intermolecular forces within simple molecular structures?

A

-Van der Waals forces of attraction
-Dipole-dipole interactions
-Hydrogen bonds

60
Q

Intermolecular forces are found between simple molecules and they determine ……………. And ……………. Points.

A

-melting
-boiling

61
Q

When we melt/boil simple molecules we do not …..

A

-break covalent bonds
-we overcome intermolecular forces

62
Q

Van der Waals forces of attraction are caused by….

A

The movement of electrons within a molecule

63
Q

What is the weakest intermolecular force?

A

-Van de Waals

64
Q

How are Van der Waals forces formed?

A

-Electron movement in first molecule induces a dipole in another, resulting in a temporary attraction between d+ on one molecule and d- on another.

65
Q

Strength of van der Waals forces are determined by..

A

-Size of the molecules (bigger mol. -> more electrons -> stronger VDW)
-Shape of molecules (straight chain can pack closer together than branched)

66
Q

Why does boiling point increase down the group of Group 0 gases?

A

-More energy level therefore more electrons each time so stronger vdw forces of attraction BETWEEN ATOMS that need more energy to overcome

67
Q

The occurrence of dipole-dipole interactions depends on:

A

-presence of electronegative atoms resulting in polar bonds ( O, F, Cl , N, Br)
-shape of the molecule (distribution of charge must be asymmetric)

68
Q

If an atom is bigger…

A

Van de Waals will be stronger

69
Q

What is the strongest type of intermolecular force?

A

Hydrogen bonding

70
Q

For hydrogen bonding to occur between molecules..

A

-A hydrogen atom must be directly bonded to electronegative elements.
-The electronegative element must have a lone pair of electrons.
-The more electronegative the element the stronger the hydrogen bond.

71
Q

Why does the strength of the hydrogen bond increase with electronegativity

A

-the greater the difference in electronegativity the greater the partial charges.
-therefore, stronger attraction between s+ on one molecule and s- on another.

72
Q

What are partial charges?

A

-difference in electronegativity causing an uneven share of electrons.

73
Q

Boiling point increases as number of hydrogen bonds in a molecules…

A

Increases

Chemistry (12 decks)

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