SNC1D Isotopes

Isotopes Isotopes are atoms of the same element that have a different number of neutrons. All isotopes will have the same number of protons but different number of neutrons. Carbon-12 Carbon-13 Carbon-14 Protons 6 Neutrons 7 8 Electrons

+ + Carbon-12 Neutrons 6 Protons 6 Electrons 6 Carbon-14 Neutrons 8 Nucleus Neutron Proton + Electrons Nucleus Nucleus Neutron Proton + Carbon-12 Neutrons 6 Protons 6 Electrons 6 Electrons Carbon-14 Neutrons 8 Protons 6 Electrons 6 Nucleus

Therefore the mass number of each isotope will be different. Isotopes Therefore the mass number of each isotope will be different. Isotopes of the same element have the same chemical properties but could have slightly different physical properties.

Learning Check! An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67

Write the atomic symbols for atoms with the following: Learning Check! Write the atomic symbols for atoms with the following: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________ 168O 3717Cl 10747Ag

Learning Check! An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is C. The element is 1) Si 2) Ca 3) Se D. Another isotope of this element is 1) 34X 2) 34X 3) 36X 16 14 14

Standard atomic notation Isotopes of Hydrogen Isotope # protons electrons neutrons Mass number Standard atomic notation Protium 1 11H Deuterium 2 21H Tritium 3 31H

Practice: How many neutrons are in each of the following isotopes? Isotopes Notation Isotopes can be indicated by writing the symbol or name of the element followed by a dash and the mass number (e.g. Carbon-14 or C-14) Isotopes of chlorine 35 17 Cl 3717Cl chlorine - 35 chlorine - 37 Practice: How many neutrons are in each of the following isotopes? Cobalt-60 Iodine-131 Uranium-235

Uses of Isotopes Carbon-14 exists in a set ratio with Carbon-12 When the organism dies, C-14 decays, but C-12 does not The percentage of C-14 decreases as the age of the dead organism increases. This percentage is used to estimate the age of the organism.

Standard atomic notation Isotope # protons # electrons # neutrons Mass number Standard atomic notation Cl-37 17 20 37 3717Cl Li-7 3 4 7 73Li Mg-25 12 13 25 2512Mg C-14 6 8 14 146C

An atom of 12C was assigned an exact mass of 12.00 amu Masses of Atoms A scale designed for atoms gives their small atomic masses in atomic mass units (amu) An atom of 12C was assigned an exact mass of 12.00 amu Relative masses of all other atoms was determined by comparing each to the mass of 12C An atom twice as heavy has a mass of 24.00 amu. An atom half as heavy is 6.00 amu.

Na 22.99 Atomic Mass Listed on the periodic table Gives the mass of “average” atom of each element compared to 12C Average atom based on all the isotopes and their abundance % Atomic mass is not a whole number

Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = 24.3 amu Mg 24.3

Calculating Atomic Mass Percent(%) abundance of isotopes Mass of each isotope of that element Weighted average = mass isotope1(%) + mass isotope2(%) + …

Learning Check Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the atomic mass of gallium?

68.9 amu x 0.602 + 70.9 amu x 0.398 Atomic mass Ga = 69.7 amu

Finding An Isotopic Mass A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope?

Determine Y in terms of X Assign X and Y values: X = % 10B Y = % 11B Determine Y in terms of X X + Y = 100 Y = 100 - X Solve for X: X (0.100) + (100 - X )(0.110) = 10.8 X = 0.20 = 20 % 10B Y = 100 - X % 11B = 100 - 20% = 80% 11B

Copper has two isotopes 63Cu (62. 9 amu) and 65Cu (64. 9 amu) Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass) 1) 30% 2) 70% 3) 100%