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chemistry yr1 > week 1 > Flashcards

week 1 Flashcards

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1
Q

vsepr stand for?

A

valence shell electron pair repulsion model

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2
Q

how do you determine the central atom of a molecule?

A

hydrogen is terminal
central atom is the atom in the earliest group
if atoms are in the same group, the larger and least electronegative atom is central

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3
Q

4 steps of vsepr?

A
  1. count valence electrons of central atom
  2. add an electron for every single bond and add 2 for every double bond around the central atom
  3. add or subtract an electron for negative or positive charges
  4. half this number to determine the number of electron pairs
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4
Q

what is vsepr used for?

A

determine 3-D shape of molecules

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5
Q

use vsepr to predict shape of CH4

A
  1. 4 valence electrons on C = 4
  2. add 4 for 4 single bonds around C = 8
  3. no +ve or -ve charges
  4. 8/2 = 4 so 4 bonding electron pairs, no lone pairs so tetrahedral
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6
Q

what shape has 3 bonding pairs and 1 lone pair?

A

trigonal pyramidal

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7
Q

what shape has 2 bonding pairs and 2 lone pairs?

A

bent

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8
Q

what shape has 5 bonding pairs and 0 lone pairs?

A

trigonal bipyramidal

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9
Q

what shape has 4 bonding pairs and 1 lone pair?

A

disphenoidal

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10
Q

what shape has 3 bonding pairs and 2 lone pairs?

A

t-shaped

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11
Q

what shape has 6 bonding pairs and 0 lone pairs?

A

octahedral

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12
Q

what shape has 5 bonding pairs and 1 lone pair?

A

square pyramidal

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13
Q

what shape has 4 bonding pairs and 2 lone pairs?

A

square planar

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14
Q

advantages and disadvantages of vsepr?

A

ads:

  • simple and mainly correct
  • works well for single bonds
  • adaptable for double bonds

disads:

  • no info on energy, bonding or reactivity
  • not 100% correct
  • doesn’t work for d-block elements
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15
Q

what does quantisation refer to in terms of subatomic particle energy

A

refers to the idea that subatomic particles cannot have any energy value and are limited to specific energy values or states

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16
Q

energy is inversely proportional to ?

A

wavelength

17
Q

what happens when H2 is exposed to high voltage

what does it tell us about

A

hydrogen atoms are created and excess energy is released in the form of light

light absorbs in to spectrum and line spectrum shows only specific energies are emitted

the energy of light emitted by hydrogen atoms is restricted to transitions between states identified by integer values

18
Q

give the equation linking energy and frequency

A

E = h𝝂
E is energy in J
h is planks constant = 6.262x10^-34 Js
𝝂 is frequency of radiation in s-1 or Hz

energy is proportional to frequency

19
Q

what is Rydberg’s equation?

what does it tell us?

A

1/λ = RHZ^2(1/n1^2 -1/n2^2)

RH is Rydberg’s constant which varies for each element
RH for hydrogen = 3.29x10^15 Hz

Z is nuclear charge
n1 and n2 are integers where n1 < n2

equation tells us that the energy of light emitted by hydrogen atoms is restricted to transitions between states, identified by integer values

20
Q

which value of n is

ground state?
ionisation?

A

n = 1 is ground state, lowest energy level

n = ∞ is an infinite distance from nucleus = ionisation of electron

21
Q

radius is proportional to ?

energy is inversely proportional to ?

A

r is proportional to n^2

E is proportional to -1/n^2

22
Q

give the equation to find the energy of a certain orbital

A

E = -RHZ^2/n^2

23
Q

what kind of system does the rydberg-bohr model work for?

A

one electron systems He+, Li2+, B3+ etc

24
Q

why did Sommerfeld modify the Bohr model?

A

on a line spectrum, more lines are visible than expected

more than one orbit can have the same energy

Sommerfeld’s modification allows orbitals to be non-circular/elliptical so they have angular momentum which must be quantised and orientation to be quantised

by quantising shapes and orbits he introduced additional energy levels corresponding to fine spectral lines

25
Q

name the 3 quantum numbers and what they represent

A

principle quantum number, n = determines energy of orbital

angular momentum quantum number, l = determines shape of an orbital

magnetic quantum number, mL = describes orientation of orbital

26
Q

what values can each quantum number take?

A

n can be any integer value = 1, 2, 3…

l is limited to 0…n-1 in integer steps

mL can be = -l…0…+l in integer steps

each orbital has a unique set of quantum numbers

27
Q

give the n, l and mL quantum numbers for 1s

A

n=1 l=0 mL=0

28
Q

name the quantum numbers for energy level 2 (2s and 2p)

A

2s:
n=2 l=0 mL=0

2p:
n=2 l=1 mL= -1, 0, +1

three mL values for 2p refers to three orientations: 2px, 2py, 2pz

29
Q

the Sommerfeld model allows for ?

A

more than one transition between levels with the name principal quantum number

can go from n=1 to n=2, l=0 OR n=2, l=1

chemistry yr1 (19 decks)

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