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chemistry: organic > topic 2 - bonding and structure > Flashcards

topic 2 - bonding and structure Flashcards

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1
Q

What are ions formed from?

A

Ions are formed when electrons are transferred from one metal atom to another non-metal atom, forming positively charged cations or negatively charged anions.

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2
Q

What do elements in the same group have in common regarding outer electrons?

A

Elements in the same group have the same number of outer electrons, so they have to lose or gain the same number to get the full outer shell, meaning they form ions with the same charges.

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3
Q

What is ionic bonding?

A

Ionic bonding is the strong electrostatic attraction between two oppositely charged ions. When oppositely charged ions form an ionic bond, an ionic compound is formed. The stronger the electrostatic attraction, the stronger the ionic bond.

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4
Q

How does ionic charge affect the strength of an ionic bond?

A

The greater the charge on an ion, the stronger the ionic bond as the stronger electrostatic attraction, therefore the higher the melting/boiling point; ions with a high charge density form stronger bonds than ions with a low charge density.

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5
Q

How do ionic radii affect ionic bond strength?

A

The smaller the ions, which can pack closer together than larger ions, the stronger the ionic bond as the stronger electrostatic attraction due to smaller distance, therefore the higher melting/boiling point.

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6
Q

What does isoelectronic mean?

A

Isoelectronic is when ions have exactly the same number and arrangement of electrons, but the number of protons increases going through the series, increasing the attraction between the positive nucleus and the electrons, decreasing the ionic radius.

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7
Q

What are giant ionic lattice structures?

A

Ionic compounds form giant ionic lattice structures, which forms because each ion is electrostatically attracted in all directions to ions of the opposite charge.

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8
Q

What is a giant structure?

A

Giant structures are crystal structures in which all the atoms or ions are linked by a network of strong bonding extending throughout the crystal.

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9
Q

What is a lattice?

A

A lattice is a three-dimensional arrangement of atoms or ions in a crystal.

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10
Q

Do different ionic compounds have the same shaped structures?

A

Different ionic compounds have different shaped structures, but they are still giant lattices.

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11
Q

What do dot and cross diagrams illustrate in ionic bonding?

A

Dot and cross diagrams show the arrangement of electrons in an atom or ion and additionally which atom the electrons in a bond originally came from.

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12
Q

How does the theory of ionic bonding fit evidence from physical properties?

A

The theory of ionic bonding fits the evidence from physical properties such as high melting points, solubility, electrical conductivity, and malleability.

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13
Q

Why do ionic compounds have high melting points?

A

Ionic compounds have high melting points because ions are held together by strong electrostatic attraction (ionic bonds) which need a lot of energy to be overcome.

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14
Q

Are ionic compounds soluble in water?

A

Ionic compounds are soluble in water but not in non-polar solvents, supporting the idea that particles are charged.

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15
Q

What happens to ions in polar vs non-polar solvents?

A

Ions are pulled apart by polar molecules like water, but not by non-polar molecules.

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16
Q

Do ionic compounds conduct electricity in solid form?

A

Ionic compounds do not conduct electricity when they’re solid, but do when molten or dissolved, as ions are fixed in position in a solid but are free to move and carry a charge as a liquid or in a solution.

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17
Q

What happens to ionic compounds when shaped?

A

Ionic compounds can’t be shaped as ions of the same charge can’t be directly over each other if the layers are pulled, leading to strong repulsion and making ionic compounds brittle (break when they are stretched or hammered)

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18
Q

What does the migration of ions in electrolysis demonstrate?

A

The migration of ions, such as when a green solution of copper (II) chromate (VI) is electrolysed, supports the idea that particles are charged, cathode turns blue due to copper (II) and anode turns yellow due to chromate (VI)

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19
Q

What are simple molecules formed from?

A

Simple molecules are formed when two or more non-metal atoms bond together and are held together by covalent bonds, but with weak forces of attraction between the molecules.

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20
Q

What is covalent bonding?

A

Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the positive nuclei of the atoms involved.

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21
Q

What do dot and cross diagrams illustrate in covalent bonding?

A

Dot and cross diagrams show how electrons behave in covalent bonds.

For covalent bonds, the number of outer electrons atoms have to lose/gain is the number of covalent bonds it forms with other atoms

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22
Q

What is dative covalent bonding?

A

Dative covalent bonding is when one atom donates both electrons to a shared pair.

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23
Q

How are positive nuclei attracted in covalent molecules?

A

In covalent molecules, the positive nuclei are attracted to the area of electron density (shared electrons) between the two nuclei.

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24
Q

What must be balanced to maintain a covalent bond?

A

To maintain the covalent bond, there has to be a balance between the attractive forces between the nuclei and the repulsive forces between the nuclei and the shared electrons.

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25
Q

What is bond length?

A

Bond length is the distance between nuclei in a covalent bond, where attractive and repulsive forces balance each other.

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26
Q

How is bond length measured?

A

Bond length is measured by X-ray diffraction (for solids) or microwave spectroscopy (if gaseous).

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27
Q

How does electron shell/atomic radius affect bond length?

A

As the distance (radius) increases, the weaker attraction between the positive nucleus and the bonding electrons results in a longer bond.

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28
Q

What effect does shielding have on bond length?

A

Inner shells create a ‘barrier’ that reduces attraction between the positive nucleus and bonding electrons, leading to a longer bond.

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29
Q

How does the number of bonds between atoms affect bond length?

A

As the number of bonding electrons increases in a single covalent bond, the stronger the attraction between the positive nucleus and the bonding electrons, resulting in a shorter bond.

30
Q

What is bond energy/enthalpy?

A

Bond energy/enthalpy is the energy required to break one mole of the bonds in a substance in the gaseous state.

31
Q

Can covalent bonding form giant structures?

A

Yes, covalent bonding can form great lattices as well as small molecules, where the giant structures have a huge network of covalently bonded atoms.

The electrostatic attraction holding the atoms together in these structures ar much stronger than the ones in simple covalent molecules.

32
Q

What evidence do giant structures provide for covalent bonding?

A

The properties of giant structures provide evidence for covalent bonding, such as high melting points, insolubility in polar solvents, lack of electrical conductivity, and good thermal conductivity.

33
Q

Why do giant structures have high melting points?

A

They have high melting points because lots of atoms are held together by many strong covalent bonds, which require a lot of energy to be overcome.

34
Q

Are giant covalent structures soluble in polar solvents?

A

No, they are insoluble in polar solvents because strong covalent bonds mean atoms are more attracted to neighbors in the lattice than to solvent molecules, supporting the idea that they don’t contain ions.

35
Q

Do giant covalent structures conduct electricity?

A

No, they do not conduct electricity as there are no charged ions or free electrons (all bonding electrons are held in localized covalent bonds).

36
Q

Why are giant covalent structures good thermal conductors?

A

They are good thermal conductors since vibrations travel easily through the stiff lattices.

37
Q

What makes the structure of giant covalent structures hard?

A

They are hard due to very strong covalent bonds throughout the lattice arrangement.

38
Q

What is metallic bonding?

A

Metallic bonding is the strong electrostatic attraction between the lattice of closely packed positive ions in a sea of delocalized electrons.

39
Q

How is the overall lattice structure of metals formed?

A

The overall lattice structure is made up of layers of positive metal ions, separated by layers of electrons.

40
Q

Why do metals have high melting points?

A

Metals have high melting points because lots of ions are held together by strong electrostatic attraction with delocalized electrons, which need a lot of energy to be overcome.

The more electrons, the stronger bonding and therefore higher melting point

41
Q

What factors affect the melting point of metals?

A

The ionic radius and lattice structure affect the melting point; smaller ionic radius results in stronger bonding and higher melting point.

42
Q

How does melting point change down a group?

A

Melting point decreases down a group due to shielding, increasing ionic radius, and decreasing attraction.

43
Q

How does melting point change along a period?

A

Melting point increases along a period due to increasing nuclear number and no effect of shielding, decreasing ionic radius, and increasing attraction.

44
Q

Are metals soluble?

A

Metals are insoluble except in liquid metals because of the strength of the metallic bond.

45
Q

Do metals conduct electricity?

A

Yes, metals are good electrical conductors as delocalized electrons are free to move throughout the whole structure and can transfer charge through the metal.

46
Q

How do impurities affect electrical conductivity in metals?

A

Impurities can dramatically reduce electrical conductivity by reducing the number of free electrons available to move and carry charge, as electrons transfer to the impurities and form anions.

47
Q

Why are metals good thermal conductors?

A

Metals are good thermal conductors as delocalized electrons can transfer kinetic energy throughout the metal.

48
Q

What is the malleability of metals?

A

Metals are malleable (can be shaped) because there are no bonds holding ions together and layers positive metal ions separated by layers of electrons, allowing layers of positive metal ions to slip/slide over each other without disrupting electrostatic attraction.

49
Q

What happens when a force is applied to a metal?

A

Layers of metal ions can slip/slide over each other easily without distrupting electrostatic attraction between metal ions and electrons.

50
Q

What is ductility in metals?

A

Metals are ductile (can be drawn into a wire) because there are no bonds holding ions together, allowing layers of positive metal ions to slip/slide over each other easily without disrupting electrostatic attraction.

51
Q

What does molecular shape depend on?

A

The molecular shape depends on the number of electron pairs in the outer shell around the central atom and the type of electron pairs surrounding the central atom.

52
Q

What does Electron-Pair Repulsion Theory state?

A

Electron-Pair Repulsion Theory states that a certain number of negatively charged electron pairs will repel each other to maximize separation and minimize repulsion.

53
Q

How do lone pairs affect bond angles?

A

Lone pairs, which are electrons not involved in bonding, repel more than bonding pairs, causing the bond angle to decrease.

54
Q

What is the effect of a lone pair in a trigonal pyramidal shape?

A

A lone pair causes the bond angle to decrease by 2.5º because the repulsion between the lone pair and bonding pairs is greater than bonding pair-bonding pair repulsion in the molecule.

55
Q

What type of shape is formed in a V-shaped molecule?

A

In a V-shaped molecule, the lone pair-lone pair repulsion is greater than the lone pair-bonding pair repulsion in trigonal pyramidal, further reducing the bond angle by an additional 2.5º.

56
Q

What is electronegativity?

A

Electronegativity is the tendency of an atom to attract a pair of electrons in a covalent bond, measured using the Pauling scale where a higher value indicates a more electronegative element.

57
Q

How does electronegativity change across a period?

A

Electronegativity increases across a period due to increased nuclear attraction, with nuclear charge increasing and electron shell/atomic radius slightly decreasing.

58
Q

How does electronegativity change down a group?

A

Electronegativity decreases down a group due to decreased nuclear attraction, as nuclear charge increases, shielding increases, and electron shell/atomic radius increases.

59
Q

Where do bonding electrons sit in a covalent bond?

A

In a covalent bond, the bonding electrons sit in orbitals between two nuclei.

60
Q

What happens when the bond between two atoms has different electronegativities?

A

When the bond has different electronegativities, the bonding electrons are pulled towards the more electronegative atom, causing an uneven charge distribution and resulting in a polar bond.

61
Q

What is a dipole in the context of electronegativity?

A

A dipole is the difference in charge between two atoms caused by a shift in electron density in the bond, resulting from the difference in electronegativity.

62
Q

What happens if a molecule has a dipole?

A

Each atom has a partial charge, where one atom is slightly positive and the other slightly negative.

63
Q

What is a dipole moment?

A

A dipole moment is a measure of the overall polarity of a molecule.

64
Q

How does the difference in electronegativity affect bond polarity?

A

The greater the difference in electronegativity, the more polar the bond becomes, leading to a larger dipole moment.

65
Q

What characterizes a non-polar bond?

A

If both atoms have similar or identical electronegativities, the electrons sit roughly midway between the two nuclei, resulting in a non-polar bond.

66
Q

What determines whether a molecule is polar?

A

Whether a molecule is polar depends on its shape and the polarity of its bonds; a polar molecule has an overall dipole due to a permanent charge across the molecule.

67
Q

What allows polar molecules to have a net dipole moment?

A

Polar molecules have polar bonds and an asymmetrical shape, allowing for a net dipole moment.

68
Q

Why might non-polar molecules have polar bonds?

A

Non-polar molecules may have polar bonds, but their symmetrical shape cancels out any dipole moments, resulting in no overall polarity.

69
Q

When can bonds between atoms be purely covalent?

A

Bonds between atoms of a single element, like diatomic gases, can be purely covalent because the electronegativity difference is zero, so bonding electrons are evenly arranged within the bond.

70
Q

Are most compounds purely ionic?

A

Very few compounds are completely ionic due to oppositely charged ions; most have some degree of covalent character, meaning ionic and covalent bonding exist on a continuous scale at the extremes.

71
Q

How does electronegativity predict bonding type?

A

Electronegativity can predict the type of bonding that will occur between two atoms; the greater the difference in electronegativity, the more ionic in character the bonding becomes.

chemistry: organic (2 decks)

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