1.2 Periodic Table Chem A

What was a key aspect of John Dalton's atomic theory in 1803?

• He arranged elements based on their chemical properties.

• He claimed all elements were built out of variable numbers of hydrogen atoms.

• He discovered the existence of Gallium, Germanium, and Scandium.

• He defined an element as a fundamental substance that could not be broken down.

What significant feature did Dmitri Mendeleev incorporate into his periodic table in 1869?

• He only included elements that were already discovered.

• He arranged elements based on their atomic number.

• He left openings for elements he believed were undiscovered.

• He grouped elements based on their physical state at room temperature.

In the periodic table, what are the vertical columns and horizontal rows called, respectively?

• Periods and Groups

• Blocks and Series

• Groups and Periods

• Rows and Columns

What does the atomic number of an element represent?

• The combined number of protons and neutrons in the nucleus.

• The number of electrons in an atom when it is at its neutral state.

• The average atomic mass of its isotopes.

• The number of neutrons in the nucleus.

Which is NOT one of the main categories of elements on the Periodic Table

• metals

• gases

• nonmetals

• metalloids