Bohr's Theory and orbitals

Question 1

continuous spectrum

Answer 1

white light passed through a prism broken up into a continuous spread of colours

Question 2

line emission spectrum

Answer 2

light from a hydrogen discharge tube is passed through a prism and coloured lines on a black backround are observed.

Question 3

why do different elements produce line emission spectra?

Answer 3

they have different electronic configurations which give rise to different electron transitions.

Question 4

limitations to bohr’s theory

Answer 4

only worked for hydrogen atoms
did not take wave particle duality of electrons into account
did not allow for heisenberg’s uncertainty principle
did not explain the discovery of sublevels

Question 5

energy levels

Answer 5

fixed energy values an electron can have in an atom. energy levels are given the letter n

Question 6

ground state

Answer 6

state where an electron occupies lowest available energy level

Question 7

excited state

Answer 7

state where electrons occupy a higher energy level than those available in the ground state

Question 8

what happens when you give an atom energy (heat or electricity)

Answer 8

the atom in the ground state absorbs a fixed amount of energy causing it to jump to a higher energy level. this atom is now in the excited state. this causes the atom to be unstable so the electron falls back to a lower energy level

Question 9

what happens when the electron falls back to a lower energy level

Answer 9

a photon of light of a fixed energy value is emitted. the energy of the photon corresponds to the energy difference between the excited state and the lower energy level.
the definite amount of energy emitted appears as a line of a particular colour in the line emission spectrum.

Question 10

use bohr’s atomic theory to explain the line emission spectra of hydrogen

Answer 10

when an atom is in the ground state electrons are restricted to energy levels that have fixed energy values and occupy the lowest available energy level.

the atom absorbs a fixed amount of energy and the e can jump to a higher energy level ie the excited state

the atom in the excited state is unstable and the e falls back down to energy level with the emission of a photon of light

the energy difference between the energy levels determines the definite frequency of the photon that appear as lines of a fixed colour on an emission spectrum

Question 11

why does hydrogen have so many electron transitions if it has only one electron

Answer 11

in a sample of hydrogen there are millions of hydrogen atoms. they don’t all absorb the same amount of energy so the electron jumps to a different higher state. when they fall back different photons of light are emitted due to the different energy levels.

Question 12

what does AAS stand for

Answer 12

Atomic Absorption spectroscopy

Question 13

what does an AAS measure?

Answer 13

the amount of light absorbed by a sample. these are dark lines on a coloured background.

Question 14

benefits of AAS

Answer 14

it is qualitative- used to detect heavy metals in water. the wavelength of light absorbed is characteristic of the element.

it is quantative: used to figure out the concentration of a sample- more light absorbed=higher the concentration.

Question 15

what is the principal behind AAS

Answer 15

atoms of the element in the ground state absorb light of a particular wavelength that is characteristic of that element

the amount of light absorbed is directly proportional to the concentration of the element in the sample. the more light absorbed=the greater no of atoms of that element.

Question 16

what instrument is used to measure an AAS

Answer 16

atomic absorbtion spectrocopy/spectrometry

Question 17

compare line emission spectra to atomic absorbtion spectra

Answer 17

line emission spectra:
coloured lines on a black background
does not tell you the concentration of a sample ie not quantitative

atomic absorbtion spectra
dark lines on a coloured background
quantitative: amount of light absorbed is directly proportional to its concentration

Question 18

what is the aim of flame tests

Answer 18

to carry out flame test analysis of different metal salts

Question 19

method of flame tests

Answer 19

1. clean a nichrome wire by dipping it into HCl and holding it into the blue flame of the bunsen burner to ensure no colour is observed on the flame.
2. dip the nichrome wire into a salt sample and hold it into the blue flame.
3. note the colour of the flame produced
4. repeat steps 1-3 using different salts.

Question 20

lithium

Answer 20

crimson

Question 21

potassium

Answer 21

lilac

Question 22

barium

Answer 22

green

Question 23

strontium

Answer 23

red

Question 24

copper

Answer 24

blue-green

Question 25

sodium

Answer 25

yellow

Question 26

sublevel

Answer 26

a subdivision of a main energy level that consists of 1 or more orbitals of the same energy

Question 27

evidence for sublevels

Answer 27

1. first ionisation energies increase across a period 2. only fixed frequencies of energy are emitted from atoms

Question 28

heisenberg's uncertainty priciple

Answer 28

it is not possible to measure, at the same time both the velocity and position of an electron

Question 29

what is the wave particle duality of electrons?

Answer 29

Electrons behave like a particle and a wave. if you want to measure the velocity of an electron it is impossible as you cannot know the exact position of an electron and visa versa. HUP and wave particle duality make it difficult to establish a covalent radius.

Question 30

why do HUP and wave particle duality make it difficult to establish a covalent radius?

Answer 30

electrons do not travel in fixed paths, so we can only know the probability of finding an electron in a particular position in an atom.

Question 31

limitations of bohr theory

Answer 31

1. only worked for hydrogen, 2.did not allow for heisenbergs uncertainty principle 3. did not explain discovery of sublevels

Question 32

modifications to bohr theory

Answer 32

electrons occupy orbitals not orbits. electrons have wave nature so we can only know the probability of finding electrons energy levels are split into sublevels

Question 33

atomic orbitals

Answer 33

a region of space where there is a high probability of finding electrons. orbitals can hold a max of 2 electrons

Question 34

what are the 4 different orbital shapes?

Answer 34

s, p, d, f

Question 35

what shape are s orbitals

Answer 35

spherical

Question 36

what shape are p orbitals

Answer 36

dumbbell

Question 37

how many orbitals does the s sublevel have

Answer 37

1

Question 38

how many orbitals does a p sublevel have

Answer 38

3

Question 39

orbitals in d sublevel

Answer 39

5

Question 40

what are the sublevels in order of energy level?

Answer 40

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d, 4f

Question 41

orbitals in f sublevel

Answer 41

7

Question 42

how many electrons in each orbital

Answer 42

2

Question 43

aufbau principle

Answer 43

electrons occupy the lowest available energy levels first.

Question 44

hund's rule of max multiplicity

Answer 44

electrons occupy orbitals singly before occupying them in pairs.

Question 45

pauli's exclusion principle

Answer 45

no more than 2 electrons can occupy an orbital + they must have an opposite spin.

Question 46

what are the exceptions when writing electronic configuration?

Answer 46

copper and chromium

Question 47

highest energy level=

Answer 47

the highest number in front of letters when writing electronic configuration.

Question 48

amount of sublevels =

Answer 48

amount of letters

Question 49

spectroscopy

Answer 49

the study of the absorption and emission of light by matter

Question 50

spectrum

Answer 50

image or info generated after matter has absorbed or emitted light

Question 51

absorption spectrum

Answer 51

dark lines on a coloured background

Question 52

atomic number

Answer 52

the total number of protons in the nucleus of an atom

Question 53

mass no

Answer 53

the no of protons and neutrons in the nucleus of an atom

Question 54

what are the 3 series of lines in the line emission spectra called

Answer 54

lyman balmer paschen

Question 55

Lyman series

Answer 55

UV region excited state to n=1

Question 56

which series of lines are invisible

Answer 56

paschen lyman

Question 57

paschen

Answer 57

IR region excited state to n=3

Question 58

which series of line is visible

Answer 58

Balmer

Question 59

Balmer

Answer 59

visible region (coloured lines in line emission spectra) excited state to n=2

Question 60

what electron transition emits a red photon

Answer 60

n=3 to n=2

Question 61

what electron transition emits a cyan photon

Answer 61

n=4 to n=2

Question 62

what electron transition emits a blue photon

Answer 62

n=5 to n=2

Question 63

what electron transition emits a purple photon

Answer 63

n=6 to n=2

Question 64

give evidence for the existence of energy levels in atoms

Answer 64

flame tests ionisation energies of elements

Question 65

why does H have so many electron transitions if it only has one e?

Answer 65

in a sample of H there are millions of H atoms. not every atom absorbs the same amount of energy, so the electrons jump to different higher excited states when these e fall from the higher energy level back to a lower energy level, photons of different energies are released which results in different lines in the emission spectrum

Question 66

give a similarity of line emission and atomic absorption spectra

Answer 66

both qualitative

Question 66

why is it difficult to specify the absolute boundary of an atom

Answer 66

due to Heisenberg's uncertainty principle

Question 66

uses of AAS

Answer 66

used to detect heavy metals in water drug tests blood alcohol conc tests

Question 67

which scientist figured out the probability of finding an e in a particular sublevel

Answer 67

Schrödinger

Question 67

compare s and p sublevel

Answer 67

S: contains 1 spherical shaped orbital holds max 2 e lower in energy P: contains 3 dumbbell shaped orbitals holds max 6 e higher in energy

Question 67

describe the difference between an atomic orbit as described by bohr and an atomic orbital

Answer 67

orbit 2D HUP not taken into account electron definitely located there orbital 3D HUP taken into account high probability of finding an e there

Question 68

using diagrams compare a p orbital and a p sublevel

Answer 68

orbital: holds max 2 e (show diagram of arrows on line) is 1 orbital (show diagram of single dumbbell orbital) sublevel holds 6 e (show same diagram but ensure to label orbitals ie xyz) contains 3 orbitals (show 3 orbitals on axis)

Question 69

explain why there is no orange or yellow line in the H emission spectrum

Answer 69

there is no transition that corresponds to those photons as e cannot exist between sublevels

Question 70

what is the e configuration of chromium

Answer 70

4s1 3d5

Question 71

why do we move one e from 4s to 3d in chromium

Answer 71

sublevels that are exactly half filled or full have extra stability the 4s and 3d sublevels are both exactly half filled which is more stable than if the 4s were full and there were 4 e in the 3d sublevel this only happens because the 4s and 3d sublevel are so close in energy

Question 72

why do we move one e from 4s to 3d in copper

Answer 72

sublevels that are exactly half filled or full have extra stability the 4s sublevel is exactly half filled and 3d sublevel is full which is more stable than if the 4s were full and there were 9 e in the 3d sublevel. this only happens because the 4s and 3d sublevel are so close in energy

Question 73

write the e configuration of copper

Answer 73

4s1 3d10