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chemistry a-level james > Chapter 2.2- Electrons,Bonding and structure > Flashcards

Chapter 2.2- Electrons,Bonding and structure Flashcards

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1
Q

How many electrons can each shell hold?

A

2n^2 number of electrons where n=shell number

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2
Q

What does n represent?

A

the principle quantum number (indicates the shell number)

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3
Q

How many electrons does the 1st shell contain?

A

2 (1)^2=2

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4
Q

How many electrons does the 2nd shell contain?

A

8

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5
Q

How many electrons does the 3rd shell contain?

A

18

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6
Q

How many electrons does the 4th shell contain?

A

32

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7
Q

What is a shell?

A

group of atomic orbitals with the same principle quantum number, n. Also known as the main energy level.

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8
Q

What model did Niels Bohr dissprove?

A

plum-pudding model, which proposed that electrons were found within a a sea of positive charge.

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9
Q

What was Bohr’s proposed model for the structure of the atom?

A

his model depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits (defined by their energy levels) around the centre.

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10
Q

What is an orbital?

A

a region around the nucleus that can hold up to two electrons, with opposite spins

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11
Q

What are the four different types of orbital?

A

s , p, d, f

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12
Q

What is the shape of an s-orbital?

A

spherical shape

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13
Q

From n=1, how many s-orbital are found in each shell?

A

1

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14
Q

What is the shape of the p-orbitals?

A

3D dumb-bell shape

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15
Q

From n=2, how many p-orbitals are found in each shell?

A

three p-orbitals, px, py and pz

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16
Q

From n=3 upwards, how many d-orbitals are found in each shell?

A

5

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17
Q

From n=4 upwards, how many f orbitals are found in each shell?

A

7

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18
Q

How many electrons can be held in each of the p orbitals in total?

A

6

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19
Q

How many electrons can be held in each of the s-orbitals in total?

A

2

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20
Q

How many electrons can be held in each of the d-orbtials in total?

A

10

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21
Q

How many electrons can be held in each of the f-orbitals in total?

A

14

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22
Q

What are orbitals that are in the same energy level grouped together called?

A

sub-shells

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23
Q

How are each orbitals represented?

A

boxes

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24
Q

How are electrons arranged in each box (orbital)

A
  • electrons have a property called spin

- the two electrons in each box (orbital) must have opposite spins

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25
Q

Within a shell, what are the sub-shells in increasing energy?

A

s, p, d, f

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26
Q

What is the name of the principle of how to work out the electron configuration of at element?

A

Aufbau principle

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27
Q

What are the three rules for electron configuration regarding the electrons in the shells of an atom?

A
  • electrons are added, one at a time, to ‘build up’ the atom

- the lowest available energy level is filled first. You can consider this level as being the closest to the nucleus.

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28
Q

What are the two rules for electron configuration regarding the sub-shells

A
  • when a sub-shell is built up with electrons, each orbital is filled singly before pairing starts
  • the 4s orbital is at a slightly lower energy level than the 3d orbital. This means 4s will fill before 3d.
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29
Q

What is the ‘last in, first out’ principle for electron configuration?

A

Electrons in the highest energy level are the first to be lost

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30
Q

What is the electron configuration of krypton?

A

1s^2, 2s^2 2p^6, 3s^2 3p^6, 4s^2 3d^10 4p^6

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31
Q

What is the electron configuration of Zn^2+?

A

1s^2, 2s^2 2p^6, 3s^2 3p^6 3d^10

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32
Q

When an atom becomes a positive ion, does the 4s or 3d sub shell empty first?

A

4s

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33
Q

What is the electron configuration of Cr?

A
  • 1s^2, 2s^2 2p^6, 3s^2 3p^6, 4s^1 3d^5
  • the 4s sub-shell isn’t full up because when the electron is added to the 3d sub-shell instead the ion is thought to be more energetically stable
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34
Q

What are the three types of chemical bond?

A
  • ionic
  • covalent
  • metallic
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35
Q

What is an ionic bond?

A

electrostatic attraction between positive and negative ions

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36
Q

Why do elements have a tendency to bond?

A

To achieve a noble gas configuration which is energetically stable

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37
Q

What are dot-and-cross diagrams?

A
  • used to show the origin of electrons in chemical bonding
  • dots are used to represent the electrons in one element, and crosses are used to represent the electrons in another element
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38
Q

Why do ionic structures form giant ionic lattices?

A
  • each ion is surrounded by oppositely charged ions

- these ions attract each other from all directions, forming a 3D giant ionic lattice

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39
Q

Name an example of an ionic compound that forms a giant ionic lattice

A
  • NaCl (sodium chloride)
  • Each Na+ is surrounded by six Cl-
  • Each Cl- is surrounded by six Na+
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40
Q

Why do ionic compound have a high melting and boiling point?

A
  • they are solid at room temperature
  • a large amount of energy is needed to break the strong electrostatic bonds that hold the oppositely charged ions together
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41
Q

Why is the melting point of MgO higher than the melting point of NaCl?

A
  • the charges on the Mg^2+ and O^2- ions are greater than those on Na^+ and Cl^-.
  • greater the charge, the stronger electrostatic forces between the ions.
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42
Q

Does a solid ionic lattice conduct electricity?

A
  • no

- the ions are held in fixed positions and no ions can move

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43
Q

When does an ionic compound conduct electricity?

A
  • when it is melted or dissolved in water

- the solid ionic lattice breaks down and the ions are free to move

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44
Q

Are ionic lattices soluble?

A

-yes in polar solvents (contains polar bonds)

45
Q

What is a polar bond?

A

atoms that do not share electrons equally, and it results in the atoms having very small charges on them

46
Q

Name a polar molecule

A
  • water (H20)
  • delta + on H atoms
  • delta - on O atoms
47
Q

How do polar water molecules break down an ionic lattice?

A
  • the slight charges within the polar molecule are able to attract the charged ions in the giant ionic lattice
  • the lattice is therefore disrupted and the ions are pulled out of it
48
Q

What does soluble mean?

A

able to be dissolved, especially in water

49
Q

What is a covalent bond?

A

strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

50
Q

What is a single covalent bond and name two examples of compounds which have single covalent bonds?

A
  • covalent bond involves one shared pair of electrons

- Chlorine (Cl2) water(H2O)

51
Q

What is a multiple covalent bond and name two examples of compounds which have multiple covalent bonds?

A
  • covalent bond which involves more than one shared pair of electrons
  • oxygen( 02) contains 2 shared pair of electrons(double bond)
  • Nitrogen (N2) contains 3 shared pair of electrons (triple bond)
52
Q

What is a dative covalent bond (coordinate bond)?

A

one atom donates both of the electrons in the covalent bond

53
Q

What is used to represent a dative covalent bond?

A

arrow

54
Q

What is an example of a compound which has dative covalent bond?

A

ammonia (NH4)

55
Q

What are the two different structures of covalent bonding?

A
  • simple molecular lattice

- giant covalent lattice

56
Q

What are simple molecular lattices?

A

-made up of small molecules
-within each molecule, the atoms are tightly held together by covalent bonds
-between the molecules, weak intermolecular forces of attraction are present
-

57
Q

Are the boiling/melting point of simple molecular substances high or high and why?

A
  • have a low melting and boiling point
  • the weak intermolecular forces of attraction between the molecules requires a small amount of energy to disrupt these forces
58
Q

Are simple molecular substances soluble?

A
  • yes in non-polar solvents
  • ‘like dissolves like’: weak intermolecular forces between the molecules of the non-polar solvent are similar to that in simple molecular substances
59
Q

Are simple molecular substances able to conduct electricity?

A
  • no

- no charged particles are free to move and carry charge

60
Q

What are giant covalent structures?

A
  • atoms are joined to adjacent atoms by strong covalent bonds
  • lots of strong covalent bonds throughout the structure
61
Q

What are two examples of giant covalent structures?

A
  • diamond
  • graphite
  • SiO2
62
Q

Do giant covalent structures have low or high melting/boiling points and why?

A
  • high melting and boiling point

- high temperatures are needed to break the strong covalent bonds within the lattice

63
Q

Are giant covalent structures able to conduct electricity?

A

-non-conductors of electricity became there are no free charged particles, except for graphite

64
Q

Are giant covalent structures soluble?

A

-not soluble in both polar and non-polar solvents because the covalent bonds in the lattice are too strong to be broken by either polar or non-polar solvents

65
Q

What is a lone pair?

A

outer shell pair of electrons that are not involved in chemical bonding

66
Q

Name two substances that have lone pairs

A
  • water(H2O0

- ammonia (NH3)

67
Q

What is the average bond enthalpy?

A
  • energy required to break a bond

- covalent bonds are not all the same strength, so some are easier to break and some are harder

68
Q

In order to achieve a noble gas configuration, how many covalent bonds do elements make?

A

-the number of bonds an element forms corresponds to the number of electrons they need in order to obtain a noble gas configuration

69
Q

How many covalent bonds does carbon, nitrogen, oxygen and hydrogen make?

A
  • carbon 4
  • nitrogen 3
  • oxygen 2
  • hydrogen 1
70
Q

What is an oxonium ion?

A
  • H30+
  • Formed when an acid is added to water
  • HCl(g) + H20(l)- —-H30+(aq) + Cl-(aq)
  • one of the lone pairs around the oxygen atom provides the bonding electrons to form a dative covalent bond
71
Q

What atoms in group 15 can expand their octet?

A
  • P

- As

72
Q

What elements in group 16 can expand their octet?

A
  • S
  • Se
  • Te
73
Q

What elements in group 17 can expand their octet?

A
  • Cl
  • Br
  • I
  • At
74
Q

What is the octet rule?

A

elements tend to combine in such a way that each atom has eight electrons in its outer shell

75
Q

What is a better rule that the octet rule?

A
  • unpaired electrons pair up

- the maximum number of electrons that can pair up is equivalent to the number of electrons in the outer shell

76
Q

What are the two things that dictate the shape of a compound or ion?

A
  • number of electron pairs around the central atom

- the nature of these pairs: bonding pairs or lone pairs

77
Q

What is the name of the shape of a molecule which has 1 bonded electron pair around the central atom and give an example?

A
  • linear

- H2

78
Q

What is the name of the shape of a molecule which has 2 bonded electron pairs around the central atom and give an example?

A
  • linear

- CO2

79
Q

What is the name of the shape of a molecule which has 3 bonded electron pairs around the central atom and give an example?

A
  • trigonal planar

- BF3

80
Q

What is the name of the shape of a molecule which has 4 bonded electron pairs around the central atom and give an example?

A
  • tetrahedral

- CH4

81
Q

What is the name of the shape of a molecule which has 5 bonded electron pairs around the central atom and give an example?

A
  • trigonal bipyramid

- PCl5

82
Q

What is the name of the shape of a molecule which has 6 bonded electron pairs around the central atom and give an example?

A
  • octahedral

- SF6

83
Q

What is the bond angle in a linear molecule, 2 bonding pairs?

A

180 degrees

84
Q

What is the bond angle in a trigonal planar molecule, 3 bonding pairs?

A

120 degrees

85
Q

What is the bond angle in a tetrahedral molecule, 4 bonding pairs?

A

109.5 degrees

86
Q

What is the bond angle/s in a trigonal bipyramid molecule, 5 bonding pairs?

A

90 and 120 degrees

87
Q

What is the bond angle in a octahedral molecule, 6 bonding pairs?

A

90 degrees

88
Q

How do molecules with lone pairs affect the bonding angles off a molecule?

A
  • a lone pair of electrons is slightly more electron dense than a bonded pair.
  • a lone pair repels more than a bonded pair. Each lone pair reduces the bond angle by about 2.5 degrees
89
Q

What shape and bond angle is an methane molecule?

A
  • tetrahedral

- 109.5 degrees

90
Q

What shape and bond angle is an a ammonia molecule?

A
  • pyramidal

- 107 degrees (3 bonding pairs and 1 lone pair)

91
Q

What shape and bond angle is a water molecule?

A
  • non-linear

- 104.5 degrees (2 bonding pairs and 2 lone pairs)

92
Q

What is meant by the term electronegativity?

A

ability of an atom to attract the bonding electrons in a covalent bond

93
Q

In the periodic table, what is the trend in electronegativity?

A

increases towards fluorine, from all directions (left to right across each period and up each group)

94
Q

What is a polar bond?

A
  • if the two bonding atoms in a covalent bond are different, their attraction for the shared pair of electrons is unequal
  • this results in a small charge difference across a bond, creating a permanent dipole
95
Q

What is a polar molecule?

A
  • a molecule that contains polar bonds

- the molecule must be non-symmetrical so the dipoles don’t cancel out

96
Q

Is water a polar molecule?

A
  • yes

- oxygen is more electronegative than hydrogen and there is an overall dipole because the molecule is not symmetrical

97
Q

Is carbon dioxide a polar molecule?

A
  • no

- oxygen has polar bonds, but there is no overall dipole because the molecule is symmetrical.

98
Q

What are the three main types of intermolecular forces?

A
  • London forces
  • permanent dipoles
  • hydrogen bonds
99
Q

What are London (dispersion) forces of attraction?

A

-caused by the constant random movement of electrons in atoms shells.
-at any moment, there will be an instantaneous (temporary) dipole across the molecule
-this induces a dipole in neighbouring molecules, which in turn induces further dipoles on their neighbouring molecules
-

100
Q

What are permanent dipole-permanent dipole interactions?

A

-if correctly alligned, two molecules which have permanent dipoles will be attracted to one another

101
Q

What are permanent dipole-induced dipole interactions?

A
  • when molecules which have permanent dipoles are near neutral molecules that are non-polar, it is able to cause electrons in the shells nearby molecule to shift slightly
  • non-polar molecule becomes slightly polar and then an attraction occurs
  • known as permanent dipole-induced dipole interaction
102
Q

What is the name given to describe permanent dipole-induced dipole interactions, permanent dipole-permanent dipole interactions and London forces?

A

van der Waals forces

103
Q

What does intermolecular forces mean?1

A

forces between molecules

104
Q

What determines the strength of London Forces?

A
  • the number of electrons

- greater the number of electrons, the stronger the forces as the induced dipoles are larger

105
Q

What are hydrogen bonds?

A
  • strong permanent dipole-permanent dipole forces of attraction
  • between an electron deficient Hydrogen atom (O-H delta +, N-H delta + or F-H delta + on one molecule and a lone pair of electrons on a highly electronegative atom (O,N of F) on a different atom
106
Q

Why is ice less dense than water as a result of hydrogen bonding?

A
  • when ice forms, water molecules arrange themselves into an orderly pattern and hydrogen bonds form between the molecules
  • ice has an open lattice with hydrogen bonds holding the water molecules far apart
107
Q

Why does water have such a high melting/boiling point?

A
  • hydrogen bonds are much stronger than other intermolecular forces
  • these strong forces must be overcome
108
Q

What are two more unique properties of water that have arisen due to hydrogen bonds?

A
  • high surface tension

- viscosity of water is high

109
Q

Rank ionic/covalent bonds, hydrogen bonds, permanent dipole-dipole and other dipole forces and London Dispersion forces in order of relative strength?

A

weakest to strongest

  1. London forces
  2. permanent dipole-dipole forces
  3. hydrogen bonds
  4. ionic/covalent bonds

chemistry a-level james (7 decks)

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