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