development of the periodic table

Question 1

how did scientists order elements before the discovery of subatomic particles?

Answer 1

by their atomic weight.

Question 2

how did Mendeleev order elements? what did this mean?

Answer 2

Mendeleev placed elements in more appropriate places, grouping elements with similar properties so patterns could be seen. This meant he sometimes left gaps or changed the order of atomic weight.

Question 3

what happened to the gaps Mendeleev left on the periodic table?

Answer 3

Elements with properties Mendeleev predicted were discovered and filled the gaps.

Question 4

how are the elements on the modern periodic table arranged?

Answer 4

The elements on the modern periodic table are arranged in order of increasing atomic number.

Question 5

what are the columns going down on the periodic table called?

Answer 5

Elements are arranged in columns called groups (going down) on the periodic table.

Question 6

what is the meaning of the groups on the periodic table?

Answer 6

The number of electrons in the outermost shell of an atom is the same as its group on the periodic table.