Fundamental Atomic Particles

Part 1Atomic Structure

Standard Atomic NotationIsotopes

Isotopic Abundance

Learning GoalsStudents will be able to:understand standard atomic notationexplain the relationship between the atomic

number and the mass number of an element, and the difference between isotopes and radioisotopes of an element

identify the scientists who contributed to the development of the modern Periodic Table

Success CriteriaStudents will be able to:writing radioactive decay equationsdetermining the number of protons, neutrons

and electrons in an atom.explaining the contributions of scientists who

developed the modern Periodic TableCalculate average atomic abundance using

isotopic abundance values

Review of Atomic Structure

Atomic Theory andThe Periodic TableReview the development of atomic theory:Read pages 14-16 for Mendeleev and DöbereinerRead pages 24-25 for Bohr and RutherfordRead page 27 for SoddyReview the information on the various

groups within the periodic table.Read pages 10-11 for basic Chemistry term and

Information on the elementsRead pages 17-19 on the groups within the

periodic table

Modern View of Atomic StructureThe atom has 2 main regions

a) Nucleus - protons and neutronsb) Electron cloud- region where you might find an electron

Rutherford’s Gold Foil experiment (remember grade 9) proved that the atom has an extremely dense, heavy nucleus surrounded by mostly empty space (save for some very light electrons).

Rutherford’s Gold Foil Experiment

The Gold Foil Experiment

The Gold Foil ExperimentThe gold foil is only

a few atoms thick.Most of the

positively charged α-particles pass straight through the gold foil

A few are deflected the tiny positively charged nuclei of the gold atoms

Density and the AtomSince most of the α-particles went through

the gold atoms in the thin gold foil, it proved that the atom was mostly composed of empty space.

Since alpha particles are positively charged (they are actually the nuclei of helium atoms), they must be deflected by a positively charged “nucleus”.

Since so few of the α-particles were deflected, the nucleus must be very small

This nucleus was determined to contain almost all of the atoms mass.

Size of an atomAtoms are small.

Measured in picometers, 10-12 metersHydrogen atoms have a 32 pm radiusIF the atom was the size of a stadium, the nucleus

would be the size of a marble.Hence most of an atom is empty space – thus you

are mostly made out of nothing.

Radius of the nucleus near 10-15m.

The density of the nucleus is near 1014 g/cm3

A dice made of a nucleus would weigh 100,000,000 tonnes (this equals 1000 supertankers).

Subatomic particles

ElectronProtonNeutron

Name

Symbol

Charge

Relative mass

Actual mass (g)

e-

p+

n0

-1+10

1/184or ≈ 0

1

1

9.11 x 10-

28

1.67 x 10-

241.67 x 10-

24

Standard Atomic Notation

Contain the symbol of the element (X), the mass number (A) and the atomic number (Z)

Xmass number (A)

atomic number (Z)

elementsymbol

12

Standard Atomic NotationRemember from grade 9:1) Symbol• 1 or 2 letter - the first is always a capitol• the symbols of many elements come from their

latin roots (ex. Gold (Au = aurum))2) Atomic Number• the number of protons in the nucleus (atom)3) Mass Number• the mass of the atom - since almost all of the

mass comes from the nucleus;• mass number = number of protons + number of

neutrons

Standard Atomic Notationthe area to the top right

of the symbol is used for ionic charge

the area to the bottom right of the symbol is used for number of atoms (ex. H2)

Standard Atomic NotationFIND THE NUMBER OF PROTONS,

NEUTRONS AND ELECTRONS FOR AN ATOM

1) Protons = atomic number2) Electrons = atomic number unless

an ionic charge is indicated (remember a positive charge indicates that electrons were LOST)

3) Neutrons = atomic mass - atomic number (can you explain this?)

Find the number of protons, neutrons and electrons for the two atoms at left

SymbolsFind the

number of protonsnumber of neutrons

number of electrons

atomic numbermass number

F19 9

16

Symbols Find the

number of protonsnumber of neutrons

number of electrons

atomic numbermass Number

Br80 35

17

Symbols If an element has an atomic

number of 34 and a mass number of 78 what is the number of protonsnumber of neutronsnumber of electrons standard atomic notation

18

Symbols If an element has 91 protons

and 140 neutrons and an ionic charge of what is the atomic numbermass numbernumber of electronscomplete symbol

19

Isotopes

IsotopesSoddy determined that atoms of the same

element can have different numbers of neutronsThis means that an element can have different

mass numbersSoddy called these atoms isotopes.Carbon has 3 isotopes, only 1 is common.

Naming IsotopesPut the mass number after the name of the

elementcarbon- 12 or C-12carbon -14 or C-14uranium-235 or U-235http://www.youtube.com/watch?v=EboWeWm

h5Pg (Tyler DeWitt _ Isotopes)

http://www.youtube.com/watch?v=n4WZ0-fItt8 (Tyler DeWitt – Isotopes and Elements examples)

Isotopes and Atomic MassFor example magnesium has 3 naturally occurring

isotopes with masses of 24, 25 and 26.What atomic mass should be placed in the periodic

table?

Scientists decided that the average weight of the atoms based on the abundance should be placed on the periodic table as the atomic mass.

This explains why mass values have decimals.http://www.youtube.com/watch?v=dRfrvpVdKGM (Tyler

DeWitt)

Determining Isotopic AbundanceThe Mass Spectrometer

Determining Isotopic Abundanceof Magnesium

Determining Isotopic AbundanceThe Mass Spectrometer

Mass Spectrometer scan of a protein found in a performance enhancing drug at the Olympics.

Mass Spectrometer read-out of Magnesium isotopes.

Try these questionsCalculate the relative atomic mass of gallium given that

the relative abundance of its two isotopes are: 60.5% of Ga-69 and 39.5% of Ga-71.

Iron has four isotopes; Fe-54 (5.82%); Fe-56 (91.66%); Fe-57 (2.19%) and Fe-58 (0.33%).  Determine the average atomic mass for natural iron.

Magnesium has three isotopes. 78.99% magnesium 24 with a mass of 23.9850 amu, 10.00% magnesium 25 with a mass of 24.9858 amu, and the rest magnesium 25 with a mass of 25.9826 amu. What is the atomic mass of magnesium? (note the more accurate data)

If not told otherwise, the mass of the isotope is the mass number in amu (atomic mass units)