Elements and the Periodic Table Chapter 3 Elements and the Periodic Table

The Periodic Table Dmitri Mendeleev: Russian chemist who listed the elements in several vertical columns in order of increasing atomic mass

The Periodic Table constructed the first periodic table (1869) -an organization of the chemical elements based on grouping the elements by similar properties worked with about 60 elements he left blank spaces in the table because there were no known elements with the appropriate properties

The Periodic Table Organized based on two characteristics: atomic weight Bonding power – the ratio of how an element combines with certain other elements on the periodic table

The Periodic Table

Patterns in the Periodic Table All atoms are composed of: Protons Neutrons Electrons

Patterns in the Periodic Table Protons determine the element Same as the atomic number Found in the nucleus Positive charge Mass of 1 atomic mass unit (amu)

Patterns in the Periodic Table Neutrons Neutral Found in the nucleus Mass of 1 amu An atom of the same element with different numbers of neutrons is called an isotope Example: Carbon- 12 or Carbon- 14

Patterns in the Periodic Table Electrons Negative charge Found outside of the nucleus Mass is very small Controls the chemical behavior of an element Valence electrons- the outer electrons that determine reactivity

Patterns in the Periodic Table Atomic number = number of protons=number of electrons Mass number = number of protons + number of neutrons Average atomic mass- on periodic table, average of all of the isotopes masses