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Chemistry A-Level > EL 3, 4, 5 > Flashcards

EL 3, 4, 5 Flashcards

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1
Q

when discussing electron shells, what is n

A

n = shell number
for the 1st shell, n=1

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2
Q

how many electrons can fit in each of the first to seventh electron shells n=1-7

A
  • n= 1 2 electrons
  • n= 2,3 8 electrons
  • n= 4,5 16 electrons
  • n= 6,7 32 electrons
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3
Q

what are the names of the different electron subshells and how many orbitals do each of them contain

A
  • s,p,d,f
  • 1 s-orbital
  • 3 p-orbitals
  • 5 d-orbitals
  • 7 f-orbitals
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4
Q

can the position of an electron be determined

A
  • no
  • no it cannot be mapped exactly
  • only the probability of finding an electron in a known region
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5
Q

describe the spins of electrons in an orbital

A
  • two electrons in an orbital that spin in opposite directions
  • spin at the same rate
  • can only occupy the same orbital if they have opposite spins (paired spins)
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6
Q

what is the shape of the s-orbital

A
  • spherical
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7
Q

what is the shape of the p-orbital

A
  • dumbbell shape
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8
Q

what is the electron configuration of an atom

A
  • the arrangement of electrons in the shells
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9
Q

how are the electrons in shells arranged

A
  • in the lowest energy arrangement possible
  • orbitals are filled in order of increasing energy
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10
Q

explain how and why you would write the electron configuration of scandium (Z=21)

A
  • the energy of the 3d subshell lies just above the 4s subshell but just below the 4p subshell
  • this means that the 4s orbital is filled before the 3d orbital
  • 1s2 2s2 2p6 3s2 3p6 3d1 4s2
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11
Q

how do you know the period of the element according to the electronic configuration

A
  • filling of 2s and 2p corresponds to period 2
  • filling of any 3 orbital means period 3 etc.
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12
Q

who proposed the modern periodic table, and describe it

A
  • Dimitri Mendeleev
  • 1869
  • in his version, the elements were arranged in order of increasing relative atomic mass
  • more arranged in order of atomic number
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13
Q

how are the elements arranged in blocks

A
  • group 1-2 S BLOCK
  • group 3-0 P BLOCK
  • transition metals D BLOCK
  • bottom section F BLOCK
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14
Q

what is periodicity

A
  • the occurrence of periodic patterns
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15
Q

what s the reason for the zig zag line in periodic table

A
  • elements to the right of the zig zag line are non metals and do not conduct electricity
  • elements to the left of the line are metals and do conduct electricity
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16
Q

what are melting or boiling points

A
  • when elements are melted or boiled the bonds, the intermolecular forces need to be over come
  • ## the strength of the IM forces is indicated by the melting or boiling point
17
Q

describe the trend in melting and boiling points across period 3

A
  • melting and boiling points initially increase up to group 3 because there is an increase in the metallic bonding
  • as you move across there is an extra electron added to the delocalised sea of electrons
  • it slightly decreases at group 4, bonding changes, but still remands high because it is a giant covalent structure so strong IM forces
  • elements from phosphorous onwards are simple structures, only joined by Vander Waals forces so they have very low melting points
  • decrease from sulphur to chlorine because the molecule size really decreases
18
Q

what is covalent bonding

A
  • when non-metallic elements react and share electrons between atoms to form a compound
19
Q

what forms a double covalent bond

A

O2, CO2

20
Q

what forms a triple covalent bond

A

N2, CO

21
Q

what is a dative covalent bond

A
  • when a pair of shared electrons in a covalent bond both come from one atom
22
Q

describe the properties of covalently bonded simple molecules

A
  • covalent intramolecular bonds are strong
  • BUT electrostatic forces between molecules are weak
  • so small amounts of energy are needed to separate one molecule from another
  • so they have low melting and boiling points
  • there are no charged particles so they do not conduct electricity
  • mostly do not dissolve in water
23
Q

describe a tetrahedral molecule and give examples

A
  • four groups of electrons around the central atom
  • electrons stay repel so they stay as far apart as possible
  • bond angle is 109.5
  • no lone pairs
    -e.g. methane
24
Q

describe a pyramidal molecule

A
  • has four groups of electrons around the central atom but one of them is a lone pair
  • electrons repel to stay as far apart as possible
  • lone pairs repel more strongly
  • bond angle of 107
  • e.g. ammonia
25
Q

describe a linear molecule

A
  • two groups of electrons around the central atom
  • bond angles of 180
  • e.g. CO2
26
Q

describe a trigonal planar molecule

A
  • three groups of electrons around the central atom
  • bond angle is 120
  • e.g. CH2O, C2H4
27
Q

describe a bipyramidal molecule

A
  • give groups of electrons around the central atom
  • one atom above the central atom, one below, and three evenly distributed around the middle
  • bond angles of 90 or 120 depending on where they are in the molecule
  • e.g. PCl5
28
Q

describe an octahedral molecule

A
  • six groups of electrons around the central atom
  • one on top of the central atom, one below, and four evenly distributed around the middle
  • bond angles of 90
  • e.g. SF6

Chemistry A-Level (26 decks)

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