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A-Level Chemistry > 2.2 Electrons, bonding and structure > Flashcards

2.2 Electrons, bonding and structure Flashcards

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1
Q

atomic orbitals definition

A

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

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2
Q

shape of s orbital

A

sphere

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3
Q

shape of p orbital

A

dumbbell / 8

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4
Q

number of orbitals in each subshell

A

s=1
p=3
d=5
f=7

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5
Q

order of orbitals

A

1s2s2p3s3p4s3d4p5s4d5p

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6
Q

ionic bonding definition

A

electrostatic attraction between positive and negative ions

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7
Q

how ionic lattices are formed in ionic compounds

A

oppositely charged ions strongly attracted in all directions

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8
Q

why ionic substances have high MP/BP

A

electrostatic forces of attraction are very strong, requiring lots of heat energy to overcome

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9
Q

solubility of ionic compounds

A

the greater the difference in charges in the ions in the compound, the less soluble they are as the polarity of water molecules isn’t enough to overcome such a strong electrostatic force of attraction

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10
Q

electrical conductivity in ionic substances

A

solid : not conductive (no free-flowing charge carriers)

melted / dissolved : conductive (free-flowing charge carriers present)

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11
Q

covalent bond definition

A

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

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12
Q

dative covalent (coordinate) bonding

A

covalent bonding when both electrons come from the same species

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13
Q

electron-pair repulsion theory

A

electron pairs surrounding central atom determines shape of molecule / ion
electron pairs as far apart as possible
arrangement of electron pairs minimises repulsion (holds bonded atoms in definite shape)
different numbers of electron pairs = different shapes

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14
Q

wedges in drawing 3D molecules on paper

A

solid line = bond in plane of paper
solid wedge = comes out of plane of paper
dotted wedge = goes into plane of paper

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15
Q

lone pair repulsion

A

slightly closer to central atom than bonded pair
occupies more space than bonded pair
repels more strongly than bonded pairs

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16
Q

bond angle between bonded pairs in tetrahedral shape (no lone pairs)

A

109.5°

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17
Q

bond angle between bonded pairs in tetrahedral shape (1 lone pair)

A

107° (decreases by 2.5° per lone pair in molecule / ion)

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18
Q

bond angle between bonded pairs in tetrahedral shape (2 lone pair)

A

104.5°

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19
Q

linear molecular shape

A

2 electron pair/ regions on same plane

180° bond angle

20
Q

trigonal planar molecular shape

A

3 electron pairs/regions

120° bond angle

21
Q

tetrahedral molecular shape

A

4 electron pairs / regions

109.5° bond angle

22
Q

octahedral molecular shape

A

6 bonded pairs / regions
90° bond angle
octahedral because atoms are positioned at corners of octahedral

23
Q

electronegativity definition

A

ability of atom to attract bonding electrons in a covalent bond
increases towards fluorine (F) in periodic table

24
Q

why water is polar but carbon is not

A

two O-H have permanent dipole
two dipoles act in different but not exactly opposing directions
two C=O have permanent dipole
bonds act in directly opposing directions so cancel each other out

25
Q

dipole definition

A

separation of opposite charges

26
Q

polar bond definition

A

partial charges present in the bond

27
Q

intermolecular forces definition

A

weak interactions between dipoles of different molecules

28
Q

London forces

A

weak intermolecular forces between all molecules (polar or non-polar)
act between induced dipoles in different molecules

29
Q

how instantaneous dipoles work

A

movement of electrons produce changing dipole in molecule (uneven distribution of electrons)
instantaneous dipole will exist but position constantly shifting

30
Q

how induced dipole-dipole interactions work

A

instantaneous induces a dipole on neighbouring molecule
induced dipole induced further dipoles on further neighbouring molecules
only temporary

31
Q

how number of electrons affect strength of induced dipole-dipole interactions

A

more electrons = larger instantaneous and induced dipoles = greater induced dipole-dipole interactions = stronger attractive forces between molecules

32
Q

how permanent dipole-dipole interactions work

A

opposite polarity between different molecules causes attraction
extra energy required to break bond as well as London forces

33
Q

simple molecular definition

A

made up of small units containing definite number of atoms with definite molecular formula
weak intermolecular forces between molecules
strong covalent bonds within molecules

34
Q

MP/BP of simple molecular substances

A

low (weak intermolecular forces easily broken)

covalent bonds NOT broken

35
Q

why non-polar simple molecular substances are soluble in non-polar solvents

A

intermolecular forces form between molecules and solvent
weakens and breaks intermolecular forces in simple molecular lattice
substance dissolves

36
Q

why non-polar simple molecular substances are insoluble in polar solvents

A

little interaction between molecules in lattice and solvent molecules
intermolecular bonding within polar solvent too strong to be broken

37
Q

solubility of polar simple molecular substances

A

may dissolve in polar solvents as polar molecules in solvent and solute attract each other (extends to liquids and gases)
depends on strength of dipole
hydrophilic parts will be polar and can interact with water
hydrophobic parts will be non-polar

38
Q

electrical conductivity of simple molecular substances

A

no mobile-charged particles that can move to complete an electrical circuit

39
Q

hydrogen bond

A

type of permanent dipole-dipole interaction
found between molecules containing electronegative atom with lone pair of electrons (e.g. O, N, F) and hydrogen atom attached to electronegative atom e.g. (H-O, H-N, H-F)
strongest intermolecular interaction

40
Q

anomalous properties of water

A

solid (ice) is less dense than liquid (water)
has relatively high MP/BP
relatively high surface tension and viscosity

41
Q

why ice is less dense than water

A

hydrogen bonds hold water molecules apart in open lattice structure
water molecules further apart in ice than water
holes in open lattice decreases density in ice
ice lattice collapses when melts and molecules move closer together

42
Q

why water has relatively high MP/BP

A

water has London forces and hydrogen bonds

more energy required to break both London forces and hydrogen bonds

43
Q

giant covalent compound properties

A

large lattices
high MP/BP (strong covalent bonds needed to be broken)
don’t conduct electricity except graphite/graphemes (no delocalised electrons)

44
Q

trigonal bipyramidal shape

A

90° and 120° bond angle

5 bonding pairs

45
Q

square planar shape

A

90°

4 bonding pairs, 2 lone pairs

A-Level Chemistry (12 decks)

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