Download Key Words Isotope- Atoms with the same number of protons but

Key Words
Isotope- Atoms with the same number of protons but different numbers of neutrons.
Atomic Mass- The average mass of all the isotopes of that element.
Mass Number- Sum of protons and neutrons.
Atomic Number- The number of protons in an atom.
Discovery of the Periodic Table
1. Russian Scientist Demitri Mendeleev discovered a set of patterns that applied to all the
elements.
2. Mendeleev noticed a pattern of properties when he arranged the elements in order of
increasing atomic mass
3. Mendeleev used the melting, point, density, color, atomic mass, and number of chemical bonds
of elements to organize the periodic table.
The modern Periodic Table
1. Periodic means “in a regular repeated pattern”.
2. In the periodic table elements properties repeat in each row or period.
3. British Scientist Henry Moseley Measured elements by the size of their positive charge (number
of protons).
4. The periodic table changed from being organized by atomic mass to its atomic number.
Organization of the periodic table
1. The properties of an element can be predicted from its location in the periodic table.
2. The table is arranged in horizontal rows called periods. There are 7 periods on the periodic
table.
3. There are 18 vertical columns called groups.
Atomic Number
1. The atomic number of an element is equal to the number of protons in an atom.
2. The atomic number can also be equal to the number of electrons if the atom is neutral.
Chemical Symbol
1. The chemical symbol is one or two letters that represent the element.
2. Most of the time the chemical symbol is an abbreviation of the elements name.
3. Sometimes the Chemical symbol is from the Latin name.
--Example: The Latin name of sodium is Natrium so its symbol is Na
Average Atomic Mass
1. The last number in the square is the average Atomic Mass
2. The atomic mass is an average because most elements consist of a mixture of isotopes.
3. The average atomic mass is determined from the combined %’s of all an elements isotopes.
Remember:
Protons= Atomic Number =Electrons
Protons+ Neutrons= Atomic Mass
Protons= Electrons(if the Atomic is neutral)