Atomic Structure 2'1: The atom

1
Atomic Structure 2.1 The atom

• 2.1.1 State the position of protons, neutrons and
  electrons in the atom
• 2.1.2 State the relative masses and relative
  charges of protons, neutrons and electrons.
• 2.1.3 Define the terms mass number (A), atomic
  number (Z) and isotopes of an element.
• 2.1.4 Deduce the symbol for an isotope given its
  mass number and atomic number.
• 2.1.5 Calculate the number of protons, neutrons
  and electrons in atoms and ions from the mass
  number, atomic number and charge.
• 2.1.6 Compare the properties of the isotopes of
  an element.
• 2.1.7 Discuss the use of radioisotopes.

2
2.1.1 State the position of protons, neutrons
and electrons in the atom

• Atomic Theory
• Democritus (420 BCE) first proposed the idea that
  matter may be made up of small, indivisible
  particles called atoms.
• Atomism developed in Chinese Arabic cultures
  during the Dark Ages in Europe.
• John Dalton (1766-1844) was the first to base
  atomic theory on scientific evidence.

3
2.1.1 State the position of protons, neutrons and
electrons in the atom

• Daltons Atomic Theory
• Elements are made of tiny particles called atoms.
• All atoms of a given element are identical. The
  atoms of a given element are different from those
  of any other element.
• Atoms of one element can combine with atoms of
  other elements to form compounds. A given
  compound always has the same relative number of
  types of atoms.
• Atoms cannot be created, nor divided into smaller
  particles, nor destroyed in the chemical process.
  A chemical reaction simply changes the way atoms
  are grouped together.

4
2.1.1 State the position of protons, neutrons and
electrons in the atom

• Evidence for sub-atomic particles
• 1897 J.J. Thomsen Cathode Ray Tube
• Evidence for electrons Bent a stream of rays
  originating from the negative electrode
  (cathode). Stream of particles with mass
  negative charge.
• 1909 Ernest Rutherford Gold Foil
• Evidence for protons nucleus Alpha particles
  deflected passing through gold foil
• 1932 James Chadwick Beryllium
• Evidence for neutrons Alpha particles caused
  beryllium to emit rays that could pass through
  lead but not be deflected,

5
2.1.1 State the position of protons, neutrons
and electrons in the atom2.1.2 State the
relative masses and relative charges of protons,
neutrons and electrons.

• Proton Located in the nucleus
• Relative charge of 1
• Relative mass of 1 amu
• Neutron Located in the nucleus
• Relative charge of 0
• Relative mass of 1 amu
• Electron Located in cloud surrounding the
  nucleus Relative charge of 1
• Relative mass of 5 x 10-4 amu
• Nucleus consists of protons and neutrons with the
• electrons surrounding the nucleus.
• In a neutral atom, the protons electrons.
• How small is an atom? Read pg. 108 Aluminum atoms

6
2.1.3 Define the terms mass number (A), atomic
number (Z), and isotope of an element

• Atomic Number (Z)
• The atomic number is the number of protons in the
  nucleus. It determines the identity of an atom.
  
• All oxygen atoms have 8 protons in the nucleus
• All lead atoms have 82 protons in the nucleus
• It also tells us the number of electrons in a
  neutral atom
• A neutral sodium atom contains 11 protons and 11
  electrons
• A neutral bromine atom contains 35 protons and 35
  electrons
• pg 115 Practice problems 7,8

7
2.1.3 Define the terms mass number (A), atomic
number (Z), and isotope of an element

• Mass Number (A)
• It is not practical to measure the masses of
  atoms in grams
• due to their small size. Scientists devised a
  measurement
• called atomic mass units.
• Protons have a mass of 1 amu
• Neutrons have mass of 1 amu
• Electrons have mass of 0 amu.
• Atomic masses of atoms protons neutrons

8
2.1.3 Define the terms mass number (A), atomic
number (Z), and isotope of an element

• Isotope
• Atoms of the same element can have different
  numbers of
• neutrons, thus they will have different atomic
  masses.
• These are called isotopes of the element.
• There are three isotopes of hydrogen
• Hydrogen-1 has 1 proton, 1 electron, 0 neutrons
• Hydrogen-2 has 1 proton, 1 electron, 1 neutron
• Hydrogen-3 has 1 proton, 1 electron, 2 neutrons

9
2.1.4 Deduce the symbol for an isotope given its
mass number and atomic number

• Consider an atom that has an atomic number of 29
  and a mass number of 63. What is its name and
  symbol?
• atomic number of 29 identifies it as copper
• Name Copper-63
• Symbol 63 Cu
• 29
• Consider an atom that has A32 and Z16. What is
  its name and symbol?
• Z16 identifies it as sulfur
• Name Sulfur-32
• Symbol 32 S
• 16

10
2.1.4 Deduce the symbol for an isotope given its
mass number and atomic number

• Consider an atom that has an atomic number of 74
  and a mass number of 185. What is its name and
  symbol?
• Consider an atom that has A127 and Z53. What is
  its name and symbol?

11
2.1.4 Deduce the symbol for an isotope given its
mass number and atomic number

• Consider an atom that has an atomic number of 74
  and a mass number of 185. What is its name and
  symbol?
• atomic number of 74 identifies it as tungsten
• Name Tungsten-185
• Symbol 185 W
• 74
• Consider an atom that has A127 and Z53. What is
  its name and symbol?
• Z53 identifies it as iodine
• Name Iodine-127
• Symbol 127 I
• 53

12
2.1.5 Calculate the number of protons, neutrons,
and electrons in atoms and ions from the mass
number, atomic number, and charge

• Consider the neutral carbon-12 atom. How many
  protons, neutrons, and electrons are in an atom
  and what is the name and symbol?
• Atomic mass 12
• Atomic number 6
• Protons 6 (atomic number)
• Neutrons 6 (mass protons)
• Electrons 6 (neutral atom so same as protons)
• Name is Carbon-12
• Symbol is 12C
• 6

13
2.1.5 Calculate the number of protons, neutrons,
and electrons in atoms and ions from the mass
number, atomic number, and charge

• Consider an atom that has 9 protons, 9 electrons,
  and 10 neutrons. What is its atomic number,
  atomic mass, name, and symbol?
• Z9 (atomic number protons
• A19 (atomic mass protons neutrons
• Fluorine-19 (name and mass)
• 19F (neutral because protons electrons)
• 9

14
2.1.5 Calculate the number of protons, neutrons,
and electrons in atoms and ions from the mass
number, atomic number, and charge

• Consider a neutral atom with A75 and Z33. How
  many protons, neutrons, and electrons are in the
  atom. What is the name and symbol?
• Consider a neutral atom with A77 and Z33. How
  many protons, neutrons, and electrons are in the
  atom. What is the name and symbol?

15
2.1.5 Calculate the number of protons, neutrons,
and electrons in atoms and ions from the mass
number, atomic number, and charge

• Consider a neutral atom with A75 and Z33. How
  many protons, neutrons, and electrons are in the
  atom. What is the name and symbol?
• Protons 33 Neutrons 42 Electrons 33
• Name Arsenic-75
• Symbol 75As
• 33
• Consider a neutral atom with A77 and Z33. How
  many protons, neutrons, and electrons are in the
  atom. What is the name and symbol?
• Protons 33 Neutrons 44 Electrons 33
• Name Arsenic-77
• Symbol 77As
• 33
• pg 116 Practice problems 9,10,11 pg 117
  Practice problems 12,13

16
2.1.5 Calculate the number of protons, neutrons,
and electrons in atoms and ions from the mass
number, atomic number, and charge

• Ions are charged particles formed when atoms gain
  or lose
• electrons resulting in unequal numbers of protons
  and electrons
• Cations Atoms that lose electrons become
  positively charged
• Anions Atoms that gain electrons become
  negatively charged
• How many protons, neutrons, and electrons are in
  an ion of K-39 that has lost one electron? What
  is the charge of the ion? What is its symbol?
• Protons 19 Neutrons 20 Electrons
  18
• Charge 1 or 1 Symbol is 39K1
• 19

17
2.1.5 Calculate the number of protons, neutrons,
and electrons in atoms and ions from the mass
number, atomic number, and charge

• The symbol of an anion is 31P 3- . Calculate the
  number of
• 15
• protons, neutrons, and electrons. What is Z and
  what is A?
• What is the symbol of a species containing 26
  protons, 30 neutrons, and 23 electrons?
• What is the symbol of a species with A56, Z26,
  and 24 electrons?

18
2.1.5 Calculate the number of protons, neutrons,
and electrons in atoms and ions from the mass
number, atomic number, and charge

• The symbol of an anion is 31P 3- . Calculate the
  number
• 15
• protons, neutrons, and electrons. What is Z and
  what is A?
• P 15 N 16 E 18 Z 15 A 31
• What is the symbol of a species containing 26
  protons, 30 neutrons, and 23 electrons?
• 56Fe 3
• 26
• What is the symbol of a species with A25, Z26,
  and 24 electrons?
• 56Fe 2
• 26

19
2.1.6 Compare the properties of the isotopes of
an element.

• Isotopes of the same element have the same
  chemical properties. However, because they have
  different masses, their physical properties such
  as density, rate of diffusion, melting point and
  boiling point will differ.
• These differences can be used to separate
  isotopes
• Separating uranium-235 for atomic bombs

20
2.1.7 Discuss the use of radioisotopes.

• Many isotopes of elements are radioactive because
  the nuclei are unstable and break down
  spontaneously.
• When they break down, these radioisotopes emit
  radiation.
• Radioisotopes can occur naturally or be created
  artificially
• Examples Carbon-14 Iodine-125 Strontium-90

• Uses of Radioisotopes
• Nuclear power generation
• Sterilization of surgical instruments
• Crime detection
• Food preservation
• Dating artifacts
• Treating and diagnosing disease

21
Atomic Structure 2.2 The mass spectrometer

• 2.2.1 Describe and explain the operation of a
  mass spectrometer
• 2.2.2 Describe how the mass spectrometer may be
  used to determine relative atomic mass using the
  12C scale.
• 2.2.3 Calculate non-integer relative atomic
  masses and abundance of isotopes from given data.

22
2.2.1 Describe and explain the operation of a
mass spectrometer

• Mass Spectrometers
• Instruments that measure charge-to-mass ratio of
  charged particles.
• Used to measure masses of isotopes as well as
  isotopic abundance
• Stages
• Vaporization heated to gas state
• Ionization turned into ions
• Acceleration high speeds
• Deflection amount depends on mass and charge of
  the ion
• Detection measures both mass-to-charge ratio and
  relative amounts of all the ions present

23
2.2.1 Describe and explain the operation of a
mass spectrometer

• Mass Spectrometer Video

24
2.2.2 Describe how the mass spectrometer may be
used to determine relative atomic mass using the
12C scale.

• Relative Atomic Mass
• Based on 12C. One amu is exactly 1/12 of the mass
  of a carbon-12 atom.
• 1 g 6.022 x 1023 amu
• 1 amu 1.660 x 10-24 g
• Atomic masses in the periodic table are
• weighted averages of the isotopes.
• To Determine Relative Atomic Mass
• Need masses of each isotopes
• Need abundance (percentage) of each isotope

Mass Spectrum of Lead
25
2.2.3 Calculate non-integer relative atomic
masses and abundance of isotopes from given data.

• Determine the atomic weight of lead using
• the data from the mass spectrum of lead
• Four isotopes 204, 206, 207, 208
• Percentage of each isotope
• Total isotopes is 10 (1225)
• 204 1/10 10 206 2/10 20
• 207 2/10 20 208 5/10 50
• Multiply the percent of each isotope by its mass
• 204 x .1 20.4 206 x .2 41.2
• 207 x .2 41.4 208 x .5 104
• Add these values
• 20.4 41.2 41.4 104 207

Mass Spectrum of Lead
26
2.2.3 Calculate non-integer relative atomic
masses and abundance of isotopes from given data.

• Three isotopes of magnesium occur in nature.
• Their abundances and masses, determined by
• mass spectrometry, are listed in the table on
• the right. Use this information to calculate the
• atomic weight of magnesium.
• Three isotopes 24, 25, 26
• Percentage of each isotope Given
• Multiply the percent of each isotope by its mass
• 23.98504 x .7899 18.95 amu
• 24.98584 x .1000 2.499 amu
• 25.98259 x .1101 2.861 amu
• Add these values 24.31 amu

27
2.2.3 Calculate non-integer relative atomic
masses and abundance of isotopes from given data.

• Calculate the atomic weight of chromium using the
  following data for the
• percent natural abundance and mass of each
  isotope
• 4.35 50Cr (49.9461 amu) 83.79 52Cr (51.9405
  amu)
• 9.50 53Cr (52.9406 amu) 2.36 54Cr (53.9389 amu)

28
2.2.3 Calculate non-integer relative atomic
masses and abundance of isotopes from given data.

• Calculate the atomic weight of chromium using the
  following data for the
• percent natural abundance and mass of each
  isotope
• 4.35 50Cr (49.9461 amu) 83.79 52Cr (51.9405
  amu)
• 9.50 53Cr (52.9406 amu) 2.36 54Cr (53.9389
  amu)
• 49.9461 x .0435 2.17 amu
• 51.9405 x .8379 43.52 amu
• 52.9406 x .0950 5.03 amu
• 53.9389 x .0236 1.27 amu
• 51.99 amu

29
2.2.3 Calculate non-integer relative atomic
masses and abundance of isotopes from given data.

• The atomic weight of gallium is 69.72 amu. The
  masses of the naturally occurring isotopes are
  68.9257 amu for 69Ga and 70.9249 amu for 71Ga.
  Calculate the percent abundance of each isotope.
• Let x the fraction of 69Ga. Then 1-x the
  fraction of 71Ga.
• 68.9257x 70.9249(1-x) 69.72 amu
• 68.9257x 70.9249 70.9249x 69.72
• -1.9992x -1.20
• x 0.600 fraction of 69Ga so 60.0 69Ga
• 1-x 0.400 fraction of 71Ga so 40.0 71Ga

30
2.2.3 Calculate non-integer relative atomic
masses and abundance of isotopes from given data.

• The atomic weight of copper is 63.546 amu. The
  masses of the two naturally occurring isotopes
  are 62.9298 amu for 63Cu and 64.9278 amu for
  65Cu. Calculate the percent of 63Cu in naturally
  occurring copper.

31
2.2.3 Calculate non-integer relative atomic
masses and abundance of isotopes from given data.

• The atomic weight of copper is 63.546 amu. The
  masses of the two naturally occurring isotopes
  are 62.9298 amu for 63Cu and 64.9278 amu for
  65Cu. Calculate the percent of 63Cu in naturally
  occurring copper.
• Let x the fraction of 63Cu. Then 1-x the
  fraction of 65Cu.
• 62.9298x 64.9278(1-x) 63.546 amu
• 62.9298x 64.9278 64.9278x 63.546
• -1.998x -1.382
• x 0.6917 fraction of 63Cu so 69.17 63Cu

32
Atomic Structure2.3 Electron Arrangement

• 2.3.1 Describe the electromagnetic spectrum
• 2.3.2 Distinguish between a continuous spectrum
  and a line spectrum
• 2.3.3 Explain how the lines in the emission
  spectrum of hydrogen are related to electron
  energy levels
• 2.3.4 Deduce the electron arrangement for atoms
  and ions up to Z20

33
2.3.1 Describe the electromagnetic spectrum

• Light consists of electromagnetic waves that can
  travel through space and matter
• All electromagnetic waves travel in a
• vacuum at 3.0 x 108 m/s (c)
• Three components of electromagnetic waves
• Amplitude Height from the origin to the crest
• Wavelength (?) Distance between the crests
• Frequency (?) Number of wave cycles to pass a
  given point per unit time
• Related by the equation c ??

34
2.3.1 Describe the electromagnetic spectrum

• Electromagnetic radiation is a form of energy.
  The energy is related to its frequency.
• The higher the frequency, the shorter the
  wavelength and the higher the energy
• E hf
• E energy (Joules)
• h Plancks constant
• (6.63 x 10-34 J s)
• F frequency (s-1)

35
2.3.2 Distinguish between a continuous spectrum
and a line spectrum

• Continuous Spectrum
• Emission showing a
• continuous range of
• wavelengths and frequencies
• Line Spectrum
• Emission of specific elements
• showing a series of discrete
• lines

36
2.3.3 Explain how the lines in the emission
spectrum of hydrogen are related to electron
energy levels

• Lyman Series Ultraviolet
• Transition of electrons from outer levels to
  n1.
• Balmer Series Visible
• Transition of electrons from outer levels to
  n2.
• Paschen Series Infrared
• Transition of electrons from outer levels to n3
  
• Spectral lines converge at increased values of n
  due to closer spacing of energy levels
• See Figure 13.17 pg. 380

37
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Models of Electron
• Arrangement
• J. J. Thomsen (1856-1940)
• Negatively charged electrons stuck into a lump
  of positively charged material. Plum Pudding
  Model
• Neils Bohr (1885-1962)
• Electrons arranged in circular paths, or orbits,
  around the nucleus. Planetary Model
• Erwin Schrodinger (1887-1961)
• Used mathematics (quantum theory) to describe
  the location and energy of an electron. Quantum
  Mechanical Model

38
2.3.4 Deduce the electron arrangement for atoms
and ions.

• The Quantum-Mechanical Model.
• Electrons are not found at certain distances from
  the nucleus but are located in a region in space
  that is described by a set of 4 quantum numbers.
  The exact location and path of the electron cant
  be determined.
• It estimates the probability of finding an
  electron within a certain volume of space
  surrounding the nucleus. Electron positions can
  be represented by a fuzzy cloud surrounding the
  nucleus (electron cloud).

39
2.3.4 Deduce the electron arrangement for atoms
and ions

• 1st Quantum Number (energy level) n
• Describes how far the electron is from the
  nucleus
• These levels are assigned values in order of
  increasing energy
• (n1,2,3,4,). The larger the number, the more
  energy the electrons have and are farther from
  the nucleus.
• 2nd Quantum Number (energy sublevel) l Describes
  the shape of the space the electron can be found
  in
• Each of the principal energy levels is divided
  into sublevels.
• n1 has 1 sublevel
• n2 has 2 sublevels
• n3 has 3 sublevels and so on

40
2.3.4 Deduce the electron arrangement for atoms
and ions.

• 2nd Quantum Number energy sublevel (l) Describes
  the shape of the space the electron can be found
  in
• There are four sublevels we will use and they are
  given letters to describe them
• s spherical shape 1s, 2s, 3s, 4s, 5s
• p dumbbell-shaped 2p, 3p, 4p, 5p
• d clover-leaf shape 3d, 4d, 5d
• f 4f, 5f,
• There are more sublevels but we wont use them.
  Each energy level contains n number of sublevels
• n1 has 1 sublevel (s)
• n2 has 2 sublevels (s,p)
• n3 has 3 sublevels (s,p,d)
• n4 has 4 sublevels (s,p,d,f)
• n5 has 5 sublevels (s,p,d,f,?)

41
2.3.4 Deduce the electron arrangement for atoms
and ions.

• 3rd quantum number orbitals (m)
• Describes how many different
• arrangements in space the
• sublevels can have.
• Every s sublevel has 1 position
• Every p sublevel has 3 positions
• Every d sublevel has 5 positions
• Every f sublevel has 7 positions
• 1s has 1 position 2p has 3 positions, 4p has 3
  positions 3d has 5 positions 5f has 7 positions

42
2.3.4 Deduce the electron arrangement for atoms
and ions.

• 4th quantum number spin (s)
• Any orbital can only have a maximum of two
• electrons, each having opposite spins.
• Every s sublevel can only have a maximum of 2
  electrons
• Every p sublevel can only have a maximum of 6
  electrons
• Every d sublevel can only have a maximum of 10
  electrons
• Every f sublevel can only have a maximum of 14
  electrons

43
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Order of Electron Fill-up
• This order must be
• followed every time
• 1s, 2s, 2p, 3s, 3p, 4s, 3d,
• 4p, 5s, 4d, 5p, 6s, 4f, 5d,
• 6p, 7s, 5f, 6d, 7p
• See pg. 367 in book

44
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Diagramming Electron Arrangement
• There are three methods for diagramming electron
• arrangement
• Electron Configuration
• Orbital Filling Diagram
• Electron Dot Diagram

45
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Electron Configuration
• Start with 1s and follow the order until all the
  electrons in
• the atom have a place.
• Draw electron configurations for the following
  elements
• H 1s1
• Be 1s22s2
• O 1s22s22p4
• Al
• Ca
• Zr

46
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Electron Configuration
• Start with 1s and follow the order until all the
  electrons in
• the atom have a place.
• Draw electron configurations for the following
  elements
• H 1s1
• Be 1s22s2
• O 1s22s22p4
• Al 1s22s22p63s23p1
• Ca 1s22s22p63s23p64s2
• Zr 1s22s22p63s23p64s23d104p65s24d2

47
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Orbital Filling
• Draw a box or circle or line for each orbital.
  Place arrows to denote electrons.
• Maximum of 2 electrons per box. The first arrow
  is pointing up, the second
• arrow is pointing down to represent opposite
  spins. Within a sublevel, each
• orbital must get an electron before the second
  electron is added
• Draw orbital filling diagrams for the following
  atoms.
• H __
• 1s
• Be __ __
• 1s 2s
• O __ __ __ __ __ 1s 2s
  2p

48
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Orbital Filling
• Draw a box or circle or line for each orbital.
  Place arrows to denote electrons.
• Maximum of 2 electrons per box. The first arrow
  is pointing up, the second
• arrow is pointing down to represent opposite
  spins. Within a sublevel, each
• orbital must get an electron before the second
  electron is added
• Draw orbital filling diagrams for the following
  atoms.
• Al
• Ca
• Zr

49
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Orbital Filling
• Draw a box or circle or line for each orbital.
  Place arrows to denote electrons.
• Maximum of 2 electrons per box. The first arrow
  is pointing up, the second
• arrow is pointing down to represent opposite
  spins. Within a sublevel, each
• orbital must get an electron before the second
  electron is added
• Draw orbital filling diagrams for the following
  atoms.
• Al __ __ __ __ __ __ __ __
  __
• 1s 2s 2p 3s 3p
• Ca __ __ __ __ __ __ __ __ __
  __
• 1s 2s 2p 3s
  3p 4s

50
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Orbital Filling
• Draw a box or circle or line for each orbital.
  Place arrows to denote electrons.
• Maximum of 2 electrons per box. The first arrow
  is pointing up, the second
• arrow is pointing down to represent opposite
  spins. Within a sublevel, each
• orbital must get an electron before the second
  electron is added
• Draw orbital filling diagrams for the following
  atom.
• Zr __ __ __ __ __ __ __ __
  __
• 1s 2s 2p 3s
  3p
• __ __ __ __ __ __ __ __ __
• 4s 3d 4p
  
• __ __ __ __ __ __
• 5s 4d

51
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Electron Dot Diagram
• Using the symbol for the element, place dots
  around the symbol corresponding
• to the outer energy level s p electrons
  (valence electrons). Will have from
• one to eight dots in the dot diagram.
• Draw electron dot diagrams for the following
  atoms
• H Be O Al Ca
  Zr
• H Be O

52
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Electron Dot Diagram
• Using the symbol for the element, place dots
  around the symbol corresponding
• to the outer energy level s p electrons. Will
  have from one to eight dots in
• the dot diagram.
• Draw electron dot diagrams for the following
  atoms
• Al Ca Zr
• Al Ca Zr

53
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Write electron configuration, orbital filling
  diagrams, and electron dot diagrams.
• Kr
• Tb

54
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Write electron configuration, orbital filling
  diagrams, and electron dot diagrams.
• Kr

55
2.3.4 Deduce the electron arrangement for atoms
and ions.

• Write electron configuration, orbital filling
  diagrams, and electron dot diagrams.
• Tb