The Atom

Essential Question?

Compare and contrast the characteristics of an atom and function of these

characteristics in an atom?

Structure of an Atom

Atom

Proton(p+)

Neutron(no)

Electron(e-)

Protonp+

• Positive Charge (p+)

• Located in the nucleus

• Mass of a proton = 1.673 x 10-24g • Relative Mass 1 amu

• Function: Gives an atom its identity – If the # of protons changes so does the type of atom

Ex: Hydrogen has 1 proton Helium has 2 protons Lithium has 3 protons

• The Atomic # always equals the # of protons

Ex: Hydrogen has an Atomic # = 1 and has 1 proton

Proton

Neutronno

• No charge

• Located in the nucleus

• Mass of a neutron 1.675 x 10-24g• Relative Mass = 1 amu• Function: Adds mass to nucleus

• Mass # - Atomic # = # of no

Ex: 1-1=0 hydrogen has 0 no

Neutron

Electrone-

• Negative charge

• Has very small mass (9.109 x 10-28g) and is not included in the atomic mass of the atom

• Relative Mass = 1/1840

• Located outside the nucleus- electron cloud- orbitals- shells- energy levels

Ex: Hydrogen has 1e-

• Function: Is responsible for an atoms behavior

Electron

• Atomic # = # protons = # electrons– Which element has 32 protons? Symbol__ Name __– Which element has 14 protons? Symbol__ Name __

• The mass number is the number of protons PLUS the number of neutrons in an atom.

• This is because the mass of the atom is mainly inside the nucleus where the protons and neutrons are found.

• The mass number – protons = number of neutrons on the Periodic Table

Find and Round the Atomic Mass to the nearest whole number

Element Symbol Average Atomic Mass

Mass Number

(round # up or down)

Ca

Barium

Cl

Nickel

Find and Round the Atomic Mass to the nearest whole number

Element Symbol Average Atomic Mass

Mass Number

(round # up or down)

Calcium Ca 40.1 amu 40 amu

Barium Ba 137.3 amu 137 amu

Chlorine Cl 35.5 amu 36 amu

Nickel Ni 58.7 amu 59 amu

Three types of atoms

Atoms can be an

Element Ion Isotope

This will help you determine which type of atom you have

• If the p+ ≠ e- then you have an ION

• If you add the p+ + no & the mass # ≠ the mass on the PT, you have an ISOTOPE

• If the mass # = the mass # on the PT, and the p+ = e- then you have an Element

Element• Cannot be broken down into simpler substances by physical or chemical

means

• Each has a symbol located on the Periodic TableEx: Ag – Silver, Pb – Lead

• Each has an atomic # and atomic massEx: Ag – Atomic # = 47

Atomic mass = 107.9 amuPb – Atomic # = 82

Atomic mass = 207.2 amu

• Atomic # = # of p+ = # of e-

• If the # of p+ = the # of e- the atom is electrically neutral

• Atomic mass = # of p+ + # of no (this number must match the rounded atomic mass (or Mass #) on the periodic table)

Element - Fill in the table belowElement Atomic # Protons Neutrons Electrons Mass #

H

He

Li

Be

B

C

N

O

F

Ne

ElementFill in the table below

Element Atomic # Protons Neutrons Electrons Mass #

H 1 1 0 1 1

He 2 2 2 2 4

Li 3 3 4 3 7

Be 4 4 5 4 9

B 5 5 6 5 11

C 6 6 6 6 12

N 7 7 7 7 14

O 8 8 8 8 16

F 9 9 10 9 19

Ne 10 10 10 10 20

Ion• An ion is an atom with a charge. The charge is either positive

or negative

• The charge depends on if the electrons are donated (lost) or accepted (gained)

Ex: If an atom donates e- then the charge becomes positive (+)

Na+

Ex: If an atom accepts e- then the charge becomes negative (-)

Cl-

• To identify an ion the # of protons will NOT equal the # of electrons

Ex: Cl normally has 17e-

A Cl- ion has 18e- (Cl has accepted 1e-)

Ion - Fill in the table belowElement Protons Electrons Gained or

Lost e-?

H 0

Li 2

Be 2

B 2

N 8

O 9

F 10

Ion - Fill in the table belowElement Protons Electrons Gained or

Lost e-?

H 1 0 Lost

Li 3 2 Lost

Be 4 2 Lost

B 5 2 Lost

N 7 8 Gained

O 8 9 Gained

F 9 10 Gained

Are the number of protons and electrons the same or different? DIFFERENT

Isotopes• Are atoms with the same number of protons but has a different

number of neutrons than the normal number of neutrons in an atom

• To calculate the # of no round the atomic mass to the nearest whole number then subtract the atomic number.

• When the atomic mass is rounded it is called the Mass number Mass number – Atomic number = # of no

Ex: (Pb) 207 – 82 = 125 neutrons

• If the atom is an isotope then there will be more neutrons and the mass will be more

Ex: (Pb) 208 – 82 = 126 neutrons

• Isotopes are neutron rich and unstable

Isotopic Notation

Ex: Silicon

Si28

14

Mass #

Atomic #

Isotopic Name

Silicon-28Mass #

Let’s Compare the Following

Carbon-12 Carbon-13 Carbon-14

Atomic #

Protons

Electrons

Mass Number

Neutrons

Let’s Compare the Following

Carbon-12 Carbon-13 Carbon-14

Atomic # 6 6 6

Protons 6 6 6

Electrons 6 6 6

Mass Number 12 13 14

Neutrons 6 7 8

How are the notations alike?

How are the above notations different?

Same protons and electrons

Different Mass # & neutrons

ReviewIsotopes are atoms of the same element with the same number of _______, but with different numbers of _______.

Answer questions 1-5 in Part I

Answer questions 6-10 in Part II

Complete Isotopes or Different Elements WS

Front and back# Statement Element(s) Different Element,

Isotope

1 Element D has 6 protons and 6 neutrons

Element F has 7 protons and 7 neutrons

2 Element J has 27 protons and 32 neutrons

Element L has 27 protons and 33 neutrons

3 Element X has 17 protons and 18 neutrons

Element Y has 18 protons and 17 neutrons

4 Element Q has 56 protons and 81 neutrons

Element R has 56 protons and 82 neutrons

5 Element T has an atomic # of 20 and an atomic mass of 40

Element Z has an atomic # of 20 and an atomic mass of 41

6 Element W has 8 protons and 8 neutrons

Element V has 7 protons and 8 neutrons

7 Element P has an atomic # of 92 and an atomic mass of 238

Element S has an atomic # of 92 and an 143 neutrons

Complete Isotopes or Different Elements WS

Front and back# Statement Element(s) Different Element,

Isotope

1 Element D has 6 protons and 6 neutrons

Element F has 7 protons and 7 neutrons

Carbon

Nitrogen

DE

2 Element J has 27 protons and 32 neutrons

Element L has 27 protons and 33 neutrons

Cobalt - 59

Cobalt - 60

Isotope

3 Element X has 17 protons and 18 neutrons

Element Y has 18 protons and 22 neutrons

Chlorine

Argone

DE

4 Element Q has 56 protons and 81 neutrons

Element R has 56 protons and 82 neutrons

Barium - 137

Barium - 138

Isotope

5 Element T has an atomic # of 20 and an atomic mass of 40

Element Z has an atomic # of 20 and an atomic mass of 41

Calcium - 40

Calcium - 41

Isotope

6 Element W has 8 protons and 8 neutrons

Element V has 7 protons and 7 neutrons

Oxygen

Nitrogen

DE

7 Element P has an atomic # of 92 and an atomic mass of 238

Element S has an atomic # of 92 and an 143 neutrons

Uranium - 238

Uranium - 235

Isotope

Element Symbol Atomic # Mass # # of p+ # of no # of e-

Helium

24

30 31

Br

13

U

11 12

Krypton

Ca

Ag 61

Fill in the Chart Below

Element Symbol Atomic # Mass # # of p+ # of no # of e-

Helium He 2 4 2 2 2

Magnesium Mg 12 24 12 12 12

Zinc Zn 30 65 30 35 31

Bromine Br 35 80 35 45 35

Aluminum Al 13 27 13 14 13

Uranium U 92 238 92 146 92

Sodium Na 11 23 11 12 12

Krypton Kr 36 84 36 48 36

Calcium Ca 20 40 20 20 20

Silver Ag 47 108 47 61 47

Fill in the Chart Below

Summarize

• Fill in Part V chart

Isotopic Notation

Isotopic Name

Atomic # # of p+ # of no # of e- Mass #

Zinc-67

17 36

Lead-207

99 155

94 244

Thallium-210

Fill in the Chart Below

Br8035

Fm260100

Isotopic Notation

Isotopic Name

Atomic # # of p+ # of no # of e- Mass #

80 205

78 200

Tungsten-191

79 112

Fill in the Chart Below

Fr23287

Isotopic Notation

Isotopic Name

Atomic # # of p+ # of no # of e- Mass #

Bromine-80 35 35 45 35 80

Zinc-67 30 30 37 30 67

Chlorine-53 17 17 36 17 53

Lead-207 82 82 125 82 207

Einsteinium-155

99 99 56 99 155

Plutonium-244 94 94 150 94 244

Fermium-260 100 100 160 100 260

Thallium-210 81 81 129 81 210

Fill in the Chart Below

Zn6730

Br8035

Fm260100

Cl5317

Pb20782

Es15599

Pu24494

Tl21081

Isotopic Notation

Isotopic Name

Atomic # # of p+ # of no # of e- Mass #

Mercury-205 80 80 125 80 205

Francium-232 87 87 145 87 232

Platinum-200 78 78 122 78 200

Tungsten-191 74 74 117 74 191

Gold-112 79 79 33 79 112

Fill in the Chart Below

Fr23287

Hg20580

Pt20078

W19174

Au11279

Summarize

• Answer questions part VI

Part VII Potassium

• K – 39 has 20 neutrons

• K – 40 has 21 neutrons

• K – 41 has 22 neutrons

K3919

K4019

K4119

Atomic Mass Determination

• Chemist have developed a method of measuring mass of an atom called:

Atomic Mass DeterminationUnit is abbreviated “amu”

• They did this because the masses of subatomic particles are so small that even scientific notation makes it hard to calculate the masses of elements.

• The atomic mass that you see on the PT is the average mass for the isotopes of that element.

• The atomic mass you see on the PT is also the isotope that is most abundant in nature!!!

• Answer Question 1 & 2

How is Atomic Mass Calculated?

• The mass on the Periodic Table is the average mass of the isotopes of an atom

• To determine the atomic mass of an atom use this formula

(Mass (amu) x Percent abundance)= Isotope A (Mass (amu) x Percent abundance)= Isotope B

Add A + B / 100 = atomic mass

Example Problem #1• Calculate the atomic mass of the unknown

element. Then identify the element using the Periodic Table?

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

185X 184.953 37.40 187X 186.956 62.60

(184.953 amu x 37.40) = 6917.35 amu(186.956 amu x 62.60) = 11703.45 amu

6917.35 amu trace/least abundant

+11703.45 amu most abundant

18620.8 / 100 = 186.2 amu

Rhenium = Re

Practice Problem #2

• Calculate the atomic mass of the unknown element. Then identify the element?

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

113X 112.904 __?__

115X 114.904 95.70

Which Isotope is trace and which is more abundant?

(112.904 amu x 4.30 ) = 485 amu(114.904 amu x 95.70) = 10996.3128 amu

485 amu trace/least abundant

+10996.3128 amu most abundant

11481.3128 / 100 = 114.81 amu

Indium = In

Practice Problems (Book)

• Pp. 104 15-17#15 Boron has 2 naturally occurring isotopes: boron-10(abundance =

19.8%, mass = 10.013 amu), boron-11 (abundance = 80.2 %, mass = 11.009 amu) Calculate the atomic mass of boron.

#16 Helium has 2 naturally occurring isotopes, helium-3 and helium-4. The atomic mass of helium is 4.003 amu. Which isotope is more abundant in nature? Explain

#17 Calculate the atomic mass of magnesium. The three magnesium isotopes have atomic masses and relative abundances of 23.995 amu (78.99%), 24.986 amu (10.00%), 25.982 amu (11.01%).

Practice Problem #1

Answer = 10.81 amu

IsotopeIsotopic notation

Mass (amu) Percent Abundance

10B 10.013 19.8 11B 11.009 80.2 5

5

Practice Problem #2

Answer = 107.9 amu

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

107Ag 106.9 51.82 109Ag 108.9 48.18 47

47

Practice Problem #3

Answer = 24.31 amu

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

24Mg 23.985 78.9925Mg 24.986 10.0026Mg 25.982 11.01

12

12

12

Practice Problem #4

Helium-4 is most abundant b/c its mass is closer to the average atomic mass on the PT

Helium-3 mass is not as close as Helium-4, so Helium-3 is less abundant

Practice Problem #5

Answer = 20.19 amu

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

20Ne 19.992 9022Ne 21.991 1010

10

Practice Problem #6

Answer = 178.55 amu

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

176Hf 176 5.00

177Hf 177 19.0

178Hf 178 27.0179Hf 179 14.0

180Hf 180 35.0

72

72

72

72

72

Practice Problem #7

Answer = 28.09 amu

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

28Si 27.977 92.2129Si 28.976 4.7030Si 29.975 3.09

14

14

14

Practice Problem #8

Answer = 107.87 amu

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

107Ag 106.905 51.83108Ag 108.905 48.1747

47

Practice Problem #9

Answer = Neon-20 Why? Its mass is closest to the average mass of neon on the PT.

IsotopeIsotopic Name

Atomic # Mass (amu)

Neon-20 10 19.992

Neon-21 10 20.994

Neon-22 10 21.991

Practice Problem #10

Answer = 83.80 amu

IsotopeIsotopic Notation

Mass (amu) Percent Abundance

78Kr 77.920 0.350

80Kr 79.916 2.27

82Kr 81.913 11.5683Kr 82.914 11.55

84Kr 83.912 56.90

86Kr 85.911 17.37

36

36

36

36

36

36

How was the Atom Discovered?

• Fill in Atomic Theory WS

• Use your book

Many early philosophers thought matter was

made up of 4 components

Earth – Air, Fire – Water

Democritus’s Ideas(384-322 B.C.)

• Matter is composed of empty space through which atoms move

• Atoms are solid homogenous, indestructible & indivisible

• Different kinds of atoms have different sizes & shapes

• The differing properties of matter are due to the size, shape and movement of atoms

• Apparent changes in matter result from changes in the grouping of atoms and not from the changes in atoms themselves

Dalton’s Ideas(1766-1844)

• All matter is composed of extremely small particles called atoms

• All atoms of a given element are identical, having the same size, mass and chemical properties. Atoms of a specific element are different than those of any other element.

• Atoms cannot be created, divided into smaller particles or destroyed.

• Different atoms combine in simple whole ratios to form compounds

• In a chemical reaction, atoms are separated, combined or rearanged.

Mendeleev’s Contribution

• Developed the Periodic Table

• Arranged the Periodic Table based on atomic mass

Roentgen’s Discovery

• X-Rays – invisible rays of e- bombarding the surface of materials

• Noticed this mysterious radiation passed through soft tissue, but not bone or metals

Currie’s Discovery

• Radioactivity – radiation

• Found Polonium, Radium

Bacquerel’s Contribution

• Phosphorescent minerals – uranium salts exposed photographic plates in dark

• Found that uranium naturally emits radiation

J. J. Thomson’s Discovery

• Determine the mass ratio of particles

• Said Dalton was wrong

• Found e-

Thompson’s Concept of the Atom

• Plum Pudding Model

• Negatively charged electrons were distributed throughout a uniform positive charge

Cathode Ray ExperimentWilliam Crookes – Accidentally found

Lead to the invention of the TV, Computer monitors(Radiation hits light producing chemicals on the backsides of screens)

• Vacuum tube – gas @ low pressure – Electric charge (-) cathode passes to (+) anode – light is electrons

• React to magnets

• Light is a stream of charged particles

• Particles have a (-) charge

Found a particle smaller than the H atom by looking at known charge to mass ratios.

WS – Cathode Ray Experiments

Rutherford’s Contribution(1871-1937)

• Found Nucleus

• Nucleus has a (+) charge

• Devised a way with H. G. Moseley to bombard elements with a cathode ray which they used to assign atomic numbers to elements

• Found - Alpha, Beta, Gamma radiation

Rutherford’s Gold Foil Experiment

• Narrow beam of alpha particles was aimed @ a thin sheet of gold foil. Zinc sulfide screen surrounding the gold foil produced a flash of light whenever it was struck by an alpha particle

WS – Understanding Rutherford’s Gold Foil Experiment

•The deflection was the alpha particle bouncing off the nucleus

Bohr’s Contribution(1885-1962)

• Model of an atom

• Small orbit = lower energy state or energy level

• Part of the Manhattan

Project

• Advocate for safe use of

Atomic energy

Chadwick’s Discovery

• Neutron

• No Charge

• Mass almost = to mass of proton

Definitions

• Atomic Mass – total average mass of an atom• Atomic number - # of p+, in an atom• Mass Number – total # of p+, & no

• Atom – Smallest particle in an element, electrically neutral, spherically shaped and composed of p+, no and e-

• Ion – An atom or bonded group of atoms w/ a (+) or (-) charge.

• Isotope – atoms of the same element w/ different # of no

Element Symbol Element, Ion,

Isotope

Atomic # Mass # Protons neutrons electrons

B

Sulfur

7

Chlorine 18

Carbon-14

31 15

13 15

Iodine-128

22 18

Complete the Following Table

Element Symbol Element, Ion,

Isotope

Atomic # Mass # Protons neutrons electrons

Boron B E 5 11 5 6 5

Sulfur S E 16 32 16 16 16

Nitrogen N E 7 14 7 7 7

Chlorine Cl Ion 17 35 17 18 18

Carbon-14 C-14 Isot 6 14 6 8 6

Phosphorus P E 15 31 15 16 15

Aluminum Al Isot 13 28 13 15 13

Iodine-128 I-128 Iso 53 128 53 75 53

Argon Ar E 18 40 18 22 18

Complete the Following Table