development of periodic table

 In the modern periodic table elements are arranged by:

• atomic mass

• valence electrons

• atomic number

• number of isotopes

  Why were there blank spaces left in Mendeleev's periodic table?                                             

•  He didn't know what to put there.

•   Undiscovered elements not yet known.

• Multiple elements could have fit

• He forgot to add the elements in

which property did Mendeleev use to order his periodic table?

• Atomic Weight

• Shielding effect

•      Electronegativity

• Metallic Character

What was Dmitri Mendeleev's greatest contribution to the history of the periodic table?

•   He arranged all of the known elements by their atomic number

• He realized that there was a pattern of reactivity which repeated every 8 elements

• He predicted the existence (and properties) of new elements

• He identified the "law of triads" which became the groups

What property did Newlands use to arrange his elements?

• Atomic mass

• Atomic size

• Number of protons

• Melting point

Mendeleev arranged the elements by their?

• Alphabetical

• Density

• melting point

• atomic mass

The horizontal rows on the periodic table are called?

• groups

• Families

• periods

• atomic numbers

Each vertical column on the periodic table is called a?

• crew

•  Period

• tower

• group

In each square of the periodic table, the number at the bottom is the?

• atomic number

• atomic mass

• chemical symbol

• element name

Most of the elements on the periodic table are classified as _____

• metals

• Nonmetals

• Metalloids

• Periods