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A level chemistry > 2.2 electrons, bonding and structure > Flashcards

2.2 electrons, bonding and structure Flashcards

1
Q

what does principle quantum number indicate

A

the shell occupied by the electron

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2
Q

what is a shell

A

a group of orbitals with the same principle quantum number

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3
Q

how many electrons can each shell hold

A

1-2
2-8
3-18
4-32

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4
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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5
Q

what are the four types of orbitals

A

s - spherical -2
p-dumbell-6
d-varied-10
f-varied-14

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6
Q

how many orbitals does p have

A

3

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7
Q

what shape is used to represent electrons when in a box

A

arrows

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8
Q

what letter is used to represent shell number

A

n

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9
Q

what are the 5 rules by which electrons are arranged in the shell

A
  • electrons are added singularly and then pair up
    -lowest energy levels are filled first
    -each energy level must be filled before the next ones
    -electrons are added one at a time
    -4s is filled before 3d
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10
Q

which electrons are lost when an atom becomes a positive ion

A

electrons in the highest energy level

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11
Q

what are the exceptions of hunds rule

A

Cr 24e- 1s2 2s2 2p6 3s2 3p6 4s1 3d5

Cu 29e- 1s2 2s2 2p6 3s2 3p6 4s1 3d10

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12
Q

what are the three main types of chemical bonds

A

ionic
covalent
metallic

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13
Q

define ionic bonding

A

the electrostatic attraction between positive and negative ions

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14
Q

define covalent bonding

A

electrostatic attraction between shared pairs of electrons and the nuclei

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15
Q

define metallic bonding

A

electrostatic attraction between the positive metal ions and the sea of delocalised electrons

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16
Q

why do giant ionic lattices conduct electricity when molten but not when solid

A

in the solid state the ions are in fixed positions and cannot move
when they are in the liquid state the ions are mobile and can freely carry the charge

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17
Q

explain why giant ionic lattices have high melting points

A

this is because a large amount of energy is needed to overcome the strong electrostatic bonds

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18
Q

in what type of solvent do ionic lattices dissolve in

A

polar

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19
Q

why are ionic compounds soluble in water

A

water has a polar bond so the molecule has a slight charge and these charges are able to attract charged ions

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20
Q

how many covalent bonds does carbon form

A

4

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21
Q

how many covalent bonds does oxygen form

A

2

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22
Q

what is a lone pair

A

electrons in the outer shell that are not involved in bonding

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23
Q

what is average bond enthalpy

A

measure of average energy needed to break the bond

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24
Q

what is a dative covalent bond

A

a bond where both of the shared electrons are supplied by one atom

denoted with an arrow

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25
Q

what does expansion of an octet

A

when a bonded atom has more than 8 electrons in its outer shell e.g SF6 PF5

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26
Q

what are the types of covalent structures

A

simple molecular lattice
giant covalent structure

27
Q

describe the bonding in simple molecular structures

A

atoms within the molecule are held by strong covalent bonds and different molecules are held together by weak intermolecular forces

28
Q

why do simple molecular structure have low melting points

A

small amounts of energy are needed to overcome the intermolecular forces

29
Q

why do covalent structures not conduct electricity

A

they have no free charged particles to move around

30
Q

what type of solvent do simple molecular structures dissolve in

A

non polar solvents

31
Q

what re some examples of giant covalent structures

A

diamond
graphite
silicon dioxide

32
Q

list 3 properties of giant covalent structures

A

high melting and boiling points

non conductors (except graphite)

insoluble in polar and non polar substances

33
Q

why does graphite conduct electricity

A

3/4 electrons are bonded so delocalised electrons are present between the layers and are able to move freely carrying charge

34
Q

why do giant covalent structures have high melting and boiling points

A

Strong covalent bonds within the molecules need to be broken which requires a lot of energy

35
Q

what does the shape of a molecule depend on

A

number of electron pairs in the outer shell

number of lone pairs

36
Q

what is the name and bond angle of a molecule with 2 bonded pairs and 0 lone pairs

A

linear
180

37
Q

what is the name and bond angle of a molecule with 3 bonded pairs and 0 lone pairs

A

trigonal planar
120

38
Q

what is the name and bond angle of a molecule with 4 bonded pairs and 0 lone pairs

A

tetrahedral
109.5

39
Q

what is the name and bond angle of a molecule with 5 bonded pairs and 0 lone pairs

A

trigonal bipyramid
90 and 120

40
Q

what is the name and bond angle of a molecule with 6 bonded pairs and 0 lone pairs

A

octahedral
90

41
Q

what is the name and bond angle of a molecule with 3 bonded pairs and 1 lone pairs

A

pyramidal
107

42
Q

what is the name and bond angle of a molecule with 2 bonded pairs and 2 lone pairs

A

bent
104.5

43
Q

how many degrees does each lone pair decrease the bond angle by

A

2.5

44
Q

what is electronegativity

A

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

45
Q

what are the most electronegative elements

A

1- flourine
oxygen
chlorine
nitrogen

46
Q

what happens to electronegativity as you go down a group

A

electronegativity decreases
this is because atomic radius increases and so does the shielding

47
Q

what happens to electronegativity as you go across a period

A

electronegativity increases as charge increases and atomic radius doesn’t

48
Q

define permanent dipole

A

a small charge difference across a bond that results from a difference in electronegativities of the bonded atoms

a polar covalent bond has a permanent dipole

49
Q

when does a molecule have a polar bond

A

when the difference in electronegativities is more than 0.5

50
Q

how do you know if a molecule is polar

A

if a shape is symmetrical the molecule isn’t polar
symmetry - central atom has no lone pairs
terminal atoms are all the same

51
Q

what are Van der Waal’s

A

they are an umbrella term for intermolecular forces(permanent dipole-permanent dipole, induced dipole- permanent dipole, london dispersion forces)
individual compounds are attracted to one another by forces called intermolecular forces

52
Q

describe permanent dipole - induced dipole interactions

A

some molecules have a permanent dipole due to polar bonds being present. And when this molecule is near to other molecules that are non-polar it is able to cause electrons in the nearby molecule to shift slightly by being repelled by the - end or attracted to the +ve end

53
Q

describe permanent dipole- permanent dipole interactions

A

molecules with permanent dipoles will be attracted to other molecules with permanent dipoles
they act a bit like bar magnets and are attracted to opposite ends

54
Q

describe London dispersion forces

A

they are caused by the constant random movement of electrons in an atoms’ shell this movement unbalances the distribution of charge
At any moment there will be an instantaneous dipole across the molecule
the instantaneous dipole induces a dipole in neighboring molecules which in turn induce further dipoles

55
Q

what is the formula and charge for ammonia

A

NH3 - 0

56
Q

what is the formula and charge for ammonium

A

NH4 +1

57
Q

What is the formula for hydroxide

A

OH -1

58
Q

what is the formula for nitrate

A

NO3 -1

59
Q

What is the formula and charge for carbonate

A

CO3 -2

60
Q

What is the formula and charge for sulfate

A

SO4 -2

61
Q

What is the formula and charge for hydrogen carbonate

A

HCO3 -1

62
Q

what is the formula and charge for dichromate

A

Cr2O2 -2

63
Q

what compounds are aqueous

A

Sodium salts
Nitrate
Ammonium
Potassium

A level chemistry (14 decks)

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