key terms: nucleons atomic number isotope atomic mass
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Atomic StructureKey Terms:
NucleonsAtomic Number
IsotopeAtomic Mass
Particles in the nucleus of atoms◦ Protons◦ Neutrons
These particles are “bound” together to form the dense positively charged nucleus that was discovered by Rutherford’s experiments
Nucleons
Equal the number of protons in the nucleus on an atom
Seen on the periodic table as a whole number
The number or protons determines the identity of the element◦ 6 protons is a carbon atom
Neutral atom-◦ Number of protons (positive)
= number of electrons (negative)
Atomic Number
Atoms of an element that have different numbers of neutrons
For carbon there are 2 predominate isotopes:◦ 12C at 98.9% abundance◦ 13C at 1.1% abundance
The above notation in known as nuclear symbol notation
There is also hyphen notation◦ Carbon-12 and Carbon-13
Isotope
Mass Spectrometry
Mass spectrometry is a method for seeing isotopes and their respective ratios
(CuI)3
Hydrogen-1◦ 1 proton and 0 neutrons
Hydrogen-2◦ 1 proton and 1 neutron
Hydrogen-3◦ 1 proton and 2 neutrons
What is the nuclear notation for these?◦ 1H◦ 2H◦ 3H
Isotopes of Hydrogen
Write the following elements in the opposite notation given.1. Copper-63
63Cu2. 7Li
Lithium-73. Silver-108
108Ag4. 22Ne
Neon-22
Example Problem #1
Total number of protons and neutrons in an atom
The mass number is always a whole number
Looking at Carbon-12, how many protons and neutrons?◦ 6 protons and 6 neutrons
Number of neutrons = mass number - protons
Electrons are ignored in mass number calculations because they weigh 1/2000th of a proton
Mass number
Example Problem #2 How many protons and neutrons are in
63Cu?◦ Atomic number = 29 number of protons◦ 63 mass number – 29 protons = 34 neutrons
How many protons and neutrons are in 39K?◦ Atomic number = 19 number of protons◦ 39 mass number – 19 protons = 20 neutrons
Average of the masses of all element’s isotopes
How do we arrive at 12.011 g/mol if protons and neutrons each weigh 1 amu?◦ The average of all of
the abundances of isotopes can be used to calculate the atomic mass of an element
Atomic Mass
Using isotopes we can solve for the Atomic Mass of an element using the following equation:
(mass of isotope A)(Percent abundance of A) + (mass of isotope B)(Percent Abundance of B) +…. = Molar Mass
Calculating Atomic Mass
Solving Atomic Mass For carbon there are 2 predominate
isotopes:◦ 12C at 98.9% abundance◦ 13C at 1.1% abundance
Molar Mass = 12*0.989 + 13*0.011Molar Mass = 11.868 + 0.143Molar Mass = 12.011 g/mol
Example Problem #3 Isotopes of potassium are:
◦ 39K at 93.26% abundance◦ 40K at 0.012% abundance◦ 41K at 6.73% abundance
Molar Mass = 39*0.9326 + 40*0.00012 + 41*0.0673Molar Mass = 36.37 + 0.0048 +2.759Molar Mass = 39.1 g/mol
Practice Problem #1 Isotopes of Silver are:
◦ 107Ag at 51.839% abundance◦ 109Ag at 48.161% abundance
Molar Mass = 107*0.51839 + 109*0.48191 Molar Mass = 55.4677 + 52.52819Molar Mass = 107.995
Subatomic Particles
Particle Charge Mass Location
Proton +1 1 amu Nucleus
Neutron Neutral 1 amu Nucleus
Electron -1 0 Electron cloud
Number of protons?◦ 26
Number of electrons?◦ 26
Number of neutrons?◦ 30
Practice Problem #2
Number of protons?◦ 8
Number of electrons?◦ 8
Number of neutrons◦ 8
Practice Problem #3
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