Your SlideShare is downloading. ×
Chapter 3.3 : Counting Atoms
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply

Chapter 3.3 : Counting Atoms

4,083
views

Published on

Published in: Education

0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
4,083
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
27
Comments
0
Likes
1
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. Counting Atoms
    Chapter 3.3
  • 2. Objectives
    Explain what isotopes are
    Define atomic number and mass number, and describe how they apply to isotopes.
    Given the identity of a nuclide, determine its number of protons, neutrons, and electrons.
    Define mole in terms of Avogadro’s number, and define molar mass.
    Solve problems involving mass in grams, amount in moles, and number of atoms of an element
  • 3. Atomic Number
    Symbol – Z
    Number of protons in nucleus of atom
    Determines the identity of the atom!!!!!
    C - 6
    He - ___
    F - ___
    Pb - ___
    Use periodic table to find these!
    Since atoms are neutral atomic number is also number of electrons
    So C also has 6 electrons
    He - ____ electrons
  • 4. Isotopes
    All Hydrogen atoms contain 1 proton
    Many naturally occurring elements can contain different numbers of neutrons.
    Isotope – at0ms of the same element that have different masses.
    n
    n
    n
    Protium
    99.985 %
    Deuterium
    0.015 %
    Tritium
    Trace
    Three isotopes of Hydrogen
  • 5. Mass Number
    Mass number – total number of protons and neutrons in the nucleus of an isotope
    Symbol – A
    Protium has 1 proton and 0 neutrons
    Mass number = #p + #n
    = 1 + 0
    = 1
    • What is the mass number deuterium and tritium?
    • 6. Find on periodic table
  • Designating Isotopes
    Hyphen Notation
    Name of atom – mass number
    Uranium - 235
    • Nuclear symbol
    • 7. A X A : mass number, Z : atomic number, X : symbol of element
    • 8. 235U
    Z
    92
    • Number of protons Neutrons Electrons
    92 143 92
    • Nuclide – general term for any isotope of any element
  • Relative Atomic Mass
    Oxygen – 16 , mass of 2.657 x 10-23 g
    Easier to use relative scale
    Need arbitrarily chosen standard
    All others are compared to carbon - 12
    • One atomic mass unit (1 amu) – exactly 1/12 the mass of a carbon – 12 atom.
    • 9. All others are compared to carbon -12
    • 10. Hydrogen – 1 , about 1/12 the mass of carbon -12
    • 11. Precise value is 1.007825 amu
    • 12. Magnesium – 24 , Slightly less than twice that of carbon -12
    • 13. Precise value is 23.985042 amu
  • Average Atomic Mass of Elements
    Most elements occur naturally as mixtures of isotopes
    Average atomic mass : weighted average of the atomic masses of the naturally occurring isotopes of an element
    Ex. of weighted average
    Box contains two types of marbles, 25% have mass of 2.00g, and 75% have a mass of 3.00 g.
    25 marbles x 2.00 g = 50 g
    75 marbles x 3.oo g = 225 g
    so 50 g + 225 g = 275 g (TOTAL MASS)
    275 g ÷ 100 = 2.75 g average marble mass
  • 14. Calculating average atomic mass
    Or
    (2.00 g x 0.25) + (3.00 g x .75) = 2.75 g
    • Calculate the average atomic mass of copper
    • 15. Use table 3-4 pg. 80 in text
    • 16. Copper - 63 69.17% with mass of 62.929599 amu
    Copper – 65 30.83% with mass of 64.927793 amu
    (0.6917 x 62.929599 amu) + (0.3083 x 64.927793 amu)
    =63.55
    Match with atomic mass on periodic table
    Round to two decimal places in calculations
  • 17. Relating Mass to Numbers of Atoms
    The MOLE
    SI base unit for amount of a substance
    Abbreviated as mol
    Defined as : amount of substance that contains as many particles as there are atoms in exactly 12 g of carbon – 12
    Counting unit just like a dozen
    We don’t order 12 or 24 eggs, we order 1 or 2 dozen
    In same way, a chemist may want 1 mol of carbon or 2 mol of iron.
    63.55 g of copper or 1 mol of copper
  • 18. Avogadro’s Number
    The number of particles in a mole – AVOGADRO’S NUMBER
    6.022 x 1023particles in exactly one mole of a pure substance
    • How big is this number?
    • 19. If every person on earth (5 billion people) counted 1 atom per second, it would take 4 million years to count all the atoms.
  • Molar Mass
    Molar mass – mass of one mole of a pure substance
    Units : g/mol
    Numerically equal to atomic mass of element
    Mass of 6.02 x 1023 atoms of element
    One mole He 6.02 x 1023atoms 4.oo g
    One mole Li 6.02 x 1023atoms6.94 g
    One mole Cu 6.02 x 1023atoms63.5o g
    One mole Fe 6.02 x 1023 atoms 55.78 g
  • 20. Gram/Mole Conversions
    Mass
    In grams
    Moles
    In mol
    Atoms
    In atoms
    Avogadro’s Number
    Molar mass
    What is the mass in grams of 3.50 mol of the element copper, Cu?
    A chemist produced 11.9 g of Aluminum, Al. How many moles of aluminum were produced?
    How many moles of silver, Ag, are in 3.01 x 1023 atoms of silver?
    What is the mass in grams of 1.20 x 1023 atoms of copper, Cu?
  • 21. The Ten Commolements
    (found at http://members.tripod.com/~smalls42/commolements.html)
    Thou shalt not use 6.02 x 1023 in vain.
    Thou shalt not use the term mole if thou has no true knowledge of the term mole.
    Thou shalt not kill a mole.
    Thou shalt not covet your neighbor's mole.
    Thou shall always remember to celebrate Mole Day.
    Thou shalt not disparage Mole Day.
    Thou shalt not use a mole out of season.
    Thou shalt always honor the one who introduced thou to Mole Day.
    You shalt always keep sacred 10/23.
    Thou shalt always remember these commolments or thou will never properly celebrate Mole Day.

×