Atomic Number, Mass Number, and Isotopes MRS. TAYLOR Chem 1A HAHS

Subatomic Particles There are three subatomic particles: 1. Electrons (negatively charged) 2. Protons (positively charged) 3. Neutrons (neutral = no charge)

Locations of the Subatomic Particles Neutrons and protons are located in the nucleus Electrons are located in orbitals surrounding the nucleus (electron cloud)

How many protons, electrons, and neutrons? Look at your periodic table. Also called the mass number

Atomic Number Is specific for each element (each element has its own atomic number) Whole number at the top of the element tile Periodic table is arranged according to increasing atomic number Never changes for a particular atom The atomic number represents the number of protons. It also represents the number of electrons because an atom is neutral The atomic number of carbon is 6. Carbon has 6 protons and 6 electrons.

Check your understanding! How many protons does titanium have? How many electrons? How many protons does tungsten have? How many electrons? How many protons does radon have? How many electrons?

Atomic Mass Also called the mass number Decimal number at the bottom of the tile Units are atomic mass units (abbreviated as amu) Represents the total number of protons and neutrons in the atom. You may round it to the nearest whole number Carbon’s atomic mass is 12 amu. It has a total of 12 protons and neutrons.

To determine the number of neutrons Subtract! Number of neutrons = atomic mass – atomic number 9 – 4 = 5 neutrons

Check your understanding! How many neutrons does platinum have? How many neutrons does manganese have? How many neutrons does mercury have?

Protons, Electrons, and Neutrons Potassium? Protons= ______ Electrons = ______ Neutrons=_______ Nickel? Copper?

Ions An atom with a charge. Two types: Cation = positively charged (Example: Mg2+) Anion = negatively charged (Example: F-1)

Ions and Electrons The charge of an atom affects the number of electrons. Cations are positive. They are loosing electrons and thereby are becoming MORE POSITIVE. Anions are negative. They are gaining electrons and thereby are becoming MORE NEGATIVE.

Example How many protons, electrons, and neutrons? O2- Al3+ F- Mg2+

Isotopes Isotopes are atoms that have the same number of protons but a different number of neutrons. As a result, isotopes of the same element have a different atomic mass. This is why the atomic mass, is a decimal number. The atomic mass is an average of all isotopes of a particular element.

Isotopes of Hydrogen

Formula for Average Atomic Mass

Example: Silicon has three isotopes. The data is below. What is the average atomic mass?   Mass Abundance Isotope 1 27.98 amu 92.21% Isotope 2 28.98 amu 4.70% Isotope 3 29.97amu 3.09%

Color Code the Periodic Table! Please make it neat and clear to read! Color the square for Hydrogen pink. Lightly color all metals yellow. Place black dots in the squares of all alkali metals. Draw a horizontal line across each box in the group of alkaline earth metals. Draw a diagonal line across each box of all transition metals. Color the metalloids purple. Color the nonmetals orange. Draw small brown circles in each box of the halogens. Draw checkerboard lines through all the boxes of the noble gases. Color all the lanthanides red. Color all the actinides green.  When you are finished, make a NEAT key underneath the title of your periodic table.