Mendeleev´s Periodic Table Flashcards

All 5 cards in this deck

How did Mendeleev arrange the elements in his periodic table?

In order of increasing relative atomic mass, placing elements with similar properties (of the elements and their compounds) in the same vertical column.

Why did Mendeleev leave gaps in his periodic table?

For elements not yet discovered, so that elements with similar properties stayed in the same group.

What did Mendeleev use the gaps in his table to do?

Predict the existence and the properties of elements not then discovered, using the properties of neighbouring elements.

Why is ordering elements by relative atomic mass not always the same as the modern order?

Because the relative abundance of isotopes makes some elements have a higher relative atomic mass than the element that follows them.
e.g. argon (40) comes before potassium (39)

True or false? Mendeleev arranged his table in order of atomic number.

False. Protons and atomic number were not known then, so he used relative atomic mass.