University:
Felician University
Course:
CHEM-001 | Basic Chemistry
Academic year:

2019
Views:

190

Pages:

10
Author:

Giselle A.

What is Mass, amu  Carbon-12 is set as the standard as having a mass of 12 amu Other elements are compared to carbon-12. Using this method  One proton has a mass of 1.0073 use 1 amu  One neutron has a mass of 1.0087 use 1 amu  One electron has a mass of 0.0006 use 0 amu What is amu? Atomic mass unit, amu Simplified unit for the mass of protons and neutrons What is mass number?  Protons and neutrons have all the mass So, all the mass is found in the nucleus (Simply count the number of protons + neutrons and you get the mass of an atom in amu!  Mass Number = # protons + # neutrons Diagram of a Lithium (Li) Atom What is Lithium’s Mass Number? What is Lithium’s Mass Number? 3 protons (3 amu) +4 neutrons (4 amu) Mass Number 7 amu What is the (Average) Atomic Mass Average atomic mass of the isotopes of an atom as found in nature. It is never a whole number. This is the Mass listed on the periodic table for an element (atom). Periodic Table Square Atomic Number Element Symbol Element Name Atomic Mass Complete summary table from your notes. Phet Activity – page 3 What is an Isotope? Atoms of the same element – Same number of protons, same atomic number Different number of neutrons, different mass number. Two isotopes of sodium. Mass Number: Mass Number: 11 protons + 12 neutrons = 23amu 11 protons + 13 neutrons = 24amu What is the Mass Number of an Isotope?  Remember: Mass Number = Number of Protons + Number of Neutrons Example: 2 isotopes of sodium, Atomic Number 11 Calculate and Compare Mass Numbers 11 protons + 12 neutrons 23 amu 11 protons + 13 neutrons vs 24 amu Check for understanding #2 Lithium Atomic Number: 3 What are the Mass Numbers of it’s 2 isotopes? 1st Isotope has 3 neutrons _____ neutrons + _____ protons = ______ amu 2nd Isotope has 4 neutrons _____ neutrons + _____ protons = ______ amu Check for understanding #2 Lithium Atomic Number: 3 What are the Mass Numbers of it’s 2 isotopes? 1st Isotope has 3 neutrons 3 neutrons + 3 protons = 6 amu protons = 7 amu 2nd Isotope has 4 neutrons 4 neutrons + 3 Isotopes & Their Uses Bone scans with radioactive technetium-99. Used to detect bone cancer. How do you name an isotope? Write out the name  add a dash (hyphen) Add the mass number  Example: Sodium-23 What is the symbol for an isotope? Called the Nuclear Symbol Show the mass number and atomic number in nuclear symbol form mass number atomic number 23 11 Na Check for understanding #3 Which of the following represent isotopes of the same element X? Identify X? A 234 B X 92 234 X 93 C 235 X 92 D 238 X 92 Answer Which of the following represent isotopes of the same element X? Identify X? A 234 B X 92 234 93 X C 235 92 X D 238 92 X Atomic Number 92 is Uranium (U)