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CHEMISTRY (AS) > Shapes of Molecules > Flashcards

Shapes of Molecules Flashcards

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1
Q

What do the following lines represent in a molecule:

  1. Line? (1 mark)
  2. Wedge? (1 mark)
  3. Broken? (1 mark)
A
  1. Flat (1)
  2. Towards you (1)
  3. Away (1)
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2
Q

What is the full method for finding the number of electron pairs from a formula? (7 marks)

A
  1. Central atom - (all atoms bonded to) (1)
  2. no. of e- in outer shell of central atom - (group no.) (1)
  3. Add 1 e- for every atom bonded to central atom - (find from formula) (1)
  4. Ion? - look at charge (add e- for -ve charge + subtract e- for +ve charge) (1)
  5. Total no. of e-s in central’s outer (1)
  6. No. of pairs - add all e-s and divide by 2 (1)
  7. No. of lone and bonding on central atom - (compare no of e-s to no. of bonds) (1)
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3
Q

Find the no. of electron pairs in a Carbon tetrafluoride, CF4 molecule? (7 marks)

A
  1. Central atom - C (1)
  2. no. of e-s in central’s outer - 4e-s (1)
  3. Add e-s per bond - 4e- (1)
  4. Ion? - no (1)
  5. Total no. of e-s in central’s outer - 4e- + 4e- = 8e- (1)
  6. No. of pairs - 8e-/2 = 4 pairs (1)
  7. No. of lone + bonding - 4 bonding, 0 lone (1)
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4
Q

Find the no. of electron pairs on Phosphorous trihydride, PH3 molecule? (7 marks)

A
  1. Central atom - P (1)
  2. No. of e-s in central’s outer - 5e- (1)
  3. Added e-s per bond - 3e- (1)
  4. Ion? - no (1)
  5. Total no. of e-s in central’s outer - 5e- + 3e- = 8e- (1)
  6. No. of lone pairs - 8e-/2 = 4 pairs (1)
  7. No. of lone + bonding - 3 bonding, 1 lone (1)
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5
Q

What is the shape and angles of molecules with central atoms with:

⦾ 2 electron pairs
⦾ 2 bonding ⦾ 0 lone

(2 marks)

A

⦾ Linear (1)

⦾ 180 (1)

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6
Q

What is the shape and angles of molecules with central atoms with:

⦾ 3 electron pairs
⦾ 3 bonding ⦾ 0 lone

(2 marks)

A

⦾ Trigonal planar (1)

⦾ 120 (1)

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7
Q

What is the shape and angles of molecules with central atoms with:

⦾ 3 electron pairs
⦾ 2 bonding ⦾ 1 lone

(2 marks)

A

⦾ ‘Bent’ / Non-linear (1)

⦾ >120 (bit) (1)

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8
Q

What is the shape and bond angles of molecules with central atoms with:

⦾ 4 electron pairs
⦾ 4 bonding ⦾ 0 lone

(2 marks)

A

⦾ Tetrahedral (1)

⦾ 109.5 (1)

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9
Q

What is the shape and angles of molecules with central atoms with:

⦾ 4 electron pairs
⦾ 3 bonding ⦾ 1 lone

(2 marks)

A

⦾ Trigonal pyramidal (1)

⦾ 107 (1)

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10
Q

What is the shape and angles of molecules with central atoms with:

⦾ 4 electron pairs
⦾ 2 bonding ⦾ 2 lone

(2 marks)

A

⦾ ‘Bent’ / Non-linear (1)

⦾ 104.5 (1)

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11
Q

What is the shape and angles of molecules with central atoms with:

⦾ 5 electron pairs
⦾ 5 bonding ⦾ 0 lone

(2 marks)

A

⦾ Trigonal bipyramidal (1)

⦾ 120 + 90 (1)

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12
Q

What is the shape and angles of molecules with central atoms with:

⦾ 5 electron pairs
⦾ 4 bonding ⦾ 1 lone

(2 marks)

A

⦾ Seesaw (1)

⦾ 102 + 86.5 (1)

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13
Q

What is the shape and angles of molecules with central atoms with:

⦾ 5 electron pairs
⦾ 3 bonding ⦾ 2 lone

(2 marks)

A

⦾ T-shape (1)

⦾ 87.5 (1)

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14
Q

What is the shape and angles of molecules with central atoms with:

⦾ 6 electron pairs
⦾ 6 bonding ⦾ 0 lone

(2 marks)

A

⦾ Octahedral (1)

⦾ 90 (1)

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15
Q

What is the shape and angles of molecules with central atoms with:

⦾ 6 electron pairs
⦾ 5 bonding ⦾ 1 lone

(2 marks)

A

⦾ Square pyramidal (1)

⦾ 90 (1)

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16
Q

What is the shape and angles of molecules with central atoms with:

⦾ 6 electron pairs
⦾ 4 bonding ⦾ 2 lone

(2 marks)

A

⦾ Square planar (1)

⦾ 90 (1)

17
Q

What is the full method for finding the shape of an unfamiliar molecule from a formula? (8 marks)

A
  1. Central atom (1)
  2. Central atom e- in outer shell (1)
  3. e- added - no. of bonds to central (1)
  4. Ion? (1)
  5. Total no. of e- in central’s outer (1)
  6. No. of pairs (1)
  7. Compare no. of pairs to no. of bonds (1)
  8. Deduce shape + bond angle + draw (1)
18
Q

Find the shape of a molecule of a BF4- ion (8 marks)

A
  1. Central atom - B (1)
  2. Central atom e- in outer shell - 3e- (1)
  3. e- added - 4e- (1)
  4. Ion? - +1e- (1)
  5. Total no. of e- in central’s outer - 3e- + 4e- + 1e- = 8e- (1)
  6. No. of pairs - 8e-/2 = 4e- (1)
  7. Compare no. of pairs to no. of bonds - 4 bonding, 0 lone (1)
  8. Deduce shape + bond angle + draw - tetrahedral, 109.5 (1)
    pg. 82
19
Q

Awkward molecules

A

IDK

CHEMISTRY (AS) (24 decks)

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