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A level Chemistry AQA > Bonding > Flashcards

Bonding Flashcards

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1
Q

Describe the shape of two pairs of electrons around a central atom (draw an example of this)

A

linear= 180 degrees apart

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2
Q

Describe the shape of three pairs of electrons around a central atom (draw an example of this)

A

Trigonal planar = 120 degrees

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3
Q

Describe the shape of four pairs of electrons around a central atom (draw an example of this)

A
  • tetrahedral = 109.5 degrees
  • 3 dimensional not planar = arrangement of the angles can be more than 360 degrees
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4
Q

Describe the shape of five pairs of electrons around a central atom (draw an example of this)

A

trigonal bipyramid

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5
Q

Describe the shape of six pairs of electrons around a central atom (draw an example of this)

A

octahedral = 90 degrees

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6
Q

Draw a molecules with 2 bonding pairs and one lone pair. Name the structure and the angles in between.

A
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7
Q

Draw a molecule with 3 bonding pairs and one lone pair. Name the structure and the angles in between.

A

107 degrees, trigonal pyramid

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8
Q

Draw a molecule with 2 bonding pairs and 2 lone pair. Name the structure and the angles in between.

A

104.5 = bent planar

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9
Q

Draw a molecule with 4 bonding pairs and 1 lone pair. Name the structure and the angles in between.

A

89 and 119 = seesaw

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10
Q

Draw a molecule with 3 bonding pairs and 2 lone pair. Name the structure and the angles in between.

A

89 degrees = t shape

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11
Q

Draw a molecule with 2 bonding pairs and 3 lone pair. Name the structure and the angles in between.

A
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12
Q

Draw a molecule with 5 bonding pairs and 1 lone pair. Name the structure and the angles in between.

A

89 degrees

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13
Q

Draw a molecule with 4 bonding pairs and 2 lone pair. Name the structure and the angles in between.

A
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14
Q

Draw a molecule with 3 bonding pairs and 3 lone pair. Name the structure and the angles in between.

A

89 degrees

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15
Q

Draw a molecule with 2 bonding pairs and 4 lone pair. Name the structure and the angles in between.

A
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16
Q

What is ionic bonding

A

the result of electrostatic attraction between oppositely charged ions

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17
Q

Name and explain the chemistry behind the properties of ionic compounds/crystals

A
  • Solids at room temperature and strong = They have giant structures, lots of energy needed to break up the lattice of ions. There are strong electrostatic attractions between ions.
  • conduct electricity when molten or dissolved in water = ions (charged particles) are free to move throughout the structure when molten, so charge is also able to move throughout the structure.
  • Brittle and shatter easily= they form a lattice of alternating positive and negative ions , so when they are hit, the ions may move and have contact between ions with the same charge, and they repel
  • soluble = water is polar, so it attracts oppositely charged ions.
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18
Q

What is covalent bonding?

A
  • covalent bond forms between a pair of non-metal atoms
  • the atoms share some of their outer electrons so they each atom has a stable noble gas arrangement
  • shared pair of electrons
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19
Q

How does sharing electrons hold atoms together?

A

held together by the electrostatic attracting between the nuclei and the shared electrons

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20
Q

What are the properties of substances with molecular structures?

A
  • low melting temperatures = strong covalent bonds are only between atoms within the molecules. there is only a weak attraction between the molecules do not need much energy to move apart from each other.
  • poor conductors of electricity = the molecules are neutral overall, so they are no charged particles to carry the current. this happens even if they dissolve in water
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21
Q

What is co-ordinate bonding?

A

when one atom provides both the electrons

  • the atom that accepts the electron pair is an atom that does not have a filled outer main level of electrons ( electron deficient)
  • the atom that is donating the electrons have a pair of electrons that is not being usied in a bond (lone pair)
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22
Q

Why are metals good conductors of electricity and heat

A
  • delocalized electrons can move throughout the structure = allows charge to flow throughout the structure
  • sea of electrons means that heat energy is spread by increasingly vigorous vibrations of the closely packed ions
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23
Q

What factors affect the strength of metals

A
  • the charge on the ion = the greater the charge on the ion, the greater the number of delocalized electrons and the stronger the electrostatic attraction been the positive ions and the electrons
  • the size of the ion - the smaller the ion, the closer the electrons are to the positive nucleus and the stronger the bond
  • delocalized electrons = these extend throughout the solid so there are o individual bonds to break.
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24
Q

Why do metals have high melting points?

A

because they have giant structures. there is a strong attraction between metal ions and the delocalized sea of electrons, making atoms difficult to separate.

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25
Q

What is electronegativity?

A

the power of an atom to attract the electron density in a covalent bond towards itself

26
Q

What is electron density?

A

the way the negative charge is distributed in a molecule

27
Q

Describe the Pauling scale

A
  • used as a measure of electronegativity
  • runs from 0 to 4
  • the greater the number = more electronegativity
28
Q

Why are noble gases 0 on the Pauling scale?

A

because, in general, they do not form covalent bonds with other atoms

29
Q

What does electronegativity depend on?

A
  • the nuclear charge (more protons) = greater attraction to shred pair of electrons
  • the distance between the nucleus and the outer shell electrons = closer means stronger attraction
  • the shielding of the nuclear charge by electrons in the inner shells= less shielding, greater attraction to shared pair of electrons
  • The smaller the atom, the closer the nucleus is to the share outer main level electrons and the greater its electronegativity
30
Q

Describe the trend in electronegativity as you go up a group in the Periodic Table

A

electronegativity increases, due to the atoms getting smaller and there is less shielding by electrons in inner shells

31
Q

Describe the trend in electronegativity as you go across a period in the Periodic Table

A

Increases = the nuclear charge increases, the shielding is constant and the atom becomes smaller

32
Q

What is polarity?

A

the unequal sharing of the electrons between atoms that are bonded together covalently

33
Q

Describe the electronegativity in a pure covalent bond

A

In a pure covalent bond, the bond must be shared equally between atoms = both atoms have exactly the same electronegativity and the bond is completely non-polar

34
Q

Describe covalent bonds between two atoms that are of a different electronegativity

A

the electrons in the bond will not be shared equally between the atoms = polar molecule. = polar bond due to s+ and s- poles

unsymmetrical electron distribution

35
Q

Why are some molecules with polar ends not a polar molecule

A

because sometimes the electrons density poles pull in opposite directions

36
Q

What are the three intermolecular forces?

A

Van der Waals forces

Dipole-dipole forces

Hydrogen bonding

37
Q

What is a dipole?

A

a difference in charge between the two atoms caused by a shift in electron density in the bond

38
Q

What a dipole-dipole forces?

A

act between molecules that have permanent dipole= weak electrostatic forces of attraction between s+ and s- charges on neighbouring molecules

39
Q

What are van der Waals forces?

A

weak electrostatic attractions that occur between positive and negative charges: happens between all atoms because they are made up of positive and negative charges.

they are in addition to any other intermolecular forces

40
Q

How do van der Waals forces work?

A

Electrons (in charge clouds) are always moving really quickly, hence their distribution is sometimes not even = temporary dipole.

This dipole can cause another temporary dipole in the opposite direction on a neighboring atom. these two dipoles are then attracted to each other. So on and so on (domino effect)

Dipoles are constantly created and destroyed, however, the overall effect is for the atoms to be attracted to each other.

The more electrons there are, the larger the temporary dipole

41
Q

What increases the strength of van der Waals?

A

the number of electrons (higher = stronger)

larger atomic masses = strong van der Waals = the number of electrons increases, and so also does the radius of the atom. The more electrons you have, and the more distance over which they can move, the bigger the possible temporary dipoles and therefore the bigger the dispersion forces.

42
Q

What is hydrogen bonding?

A

when a hyrogern atom (s+) interacts with a more electronegative atom with a s- charge (oxygen, fluorine, nitrogen are the only elements electronegative enough), attracted to lone pairs (but doesn’t form dative bonds)

43
Q

Why is hydrogen bonding so strong?

A

Hydrogen atoms become very electron deficient when bonding to fluorine, nitrogen and oxygen. This is because these elements are very electronegative and attracts the shared electrons in the bond towards it. Hydrogen (s+) atoms are very small. These exposed protons have a very strong electric field because of heir small size. Lone pairs also become strongly attracted to the electron deficient hydrogen

44
Q

What is the electron pair repulsion theory?

A
  • each pair of electrons around an atom ill repel all other electron pairs
  • the pairs of electrons will therefore take up a position as far apart as possible to minimize repulsion
45
Q

Describe what happens when you heat a solid?

A

energy is supplied to the particles = makes them vibrate more about a fixed position = slightly increases the average distance between the particles and so the solid expands

46
Q

What happens during fusion?

A

A solid is supplied with so much energy that the forces that act between the solid particles are weakened = liquid. the energy required for this to happen i called enthalpy change of melting

47
Q

Why doesn’t the temperature change whiles the solid is melting?

A

because the heat energy provided is absorbed as the forces between particles are weakened.

48
Q

What happens during vaporization?

A

lots of energy is supplied to the liquid to break all of the intermolecular forces between the particles (as gas move freely and independently). The energy required to do this is called the enthalpy change of vaporisation

49
Q

What happens when you heat a gas?

A

the particles gain kinetic energy and move faster. they get much further apart (expand greatly). this increases the pressure when in a container.

50
Q

Describe the bonding and properties of molecular crystals (iodine)

A
  • covalent bonds within the molecules and intermolecular forces between them
  • low melting/boiling point and brittle: weak van der Waals forces
  • poor electrical conductivity= no ions to conduct and electrons localised
  • poor solubility = iodine is non-polar. Water is polar, so water molecules remain hydrogen-bonded with each other, rather than forming van der Waals with iodine.
51
Q

What is the structure and what are the properties of diamond?

A

4 single covalent bonds between carbon atoms

very high melting point = thousands of strong covalent bonds between carbon atoms= lots of energy needed to overcome

no electrical conductivity = no delocalized electrons, all electrons used in covalent bonds

very hard and strong = structure very rigid, arrangement of atoms held by covalent bonds

insoluble= no charged particles, so water is not attracted to it. water is not strong enough to break covalent bonds.

52
Q

What is the structure and what are the properties of graphite?

A
  • each carbon atom forms three single covalent bonds to other carbon atoms
  • very high melting and boiling points = thousands of strong covalent bonds between carbon atoms in the layers = lots of energy needed
  • very good electrical conductivity= delocalized electrons can move throughout the structure, so charge can flow through the structure
  • very strong = due to its unbroken pattern and the strong covalent bonds between carbon atoms
  • flexible= strong bonds between carbon atoms are flexible, can be twisted without breaking
53
Q

What is the property of ice?

A

low melting and boiling point: hydrogen bonds between molecules are weak

no electrical conductivity: no complete ions to allow charge through structure

less dense: in ice, water molecules have 4 hydrogen bonds and are in a rigid structure. In water, hydrogen bonds are being constantly made and broken, allowing the water molecules to be closer to each other= more water molecules per cm^3= more dense

54
Q

Why is graphite soft?

A

weak forces between planes

55
Q

Suggest why lone pairs are sometimes opposite from each other

A

lone pairs repel more, so they are the furthest away from each other

56
Q

What is the formula for the compound ion sulfate?

A

SO42-

57
Q

What is the formula for the compound ion hydroxide ?

A

OH-

58
Q

What is the formula for the compound ion nitrate?

A

NO3-

59
Q

What is the formula for the compound ion carbonate?

A

CO3-2

60
Q

What is the formula for the compound ion ammonium?

A

NH4+

A level Chemistry AQA (30 decks)

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