The periodic table

Question 1

What do the groups tell us?

Answer 1

Elements in the same group have similar chemical properties as they have the same number of electrons in their outer shell

Question 2

What do the periods tell us?

Answer 2

Number of shells in each atom

Question 3

Describe how Mendeleev arranged the elements, known at that time, in a periodic table

Answer 3

• He arranged them (mostly) in order of relative atomic masses, leaving gaps for new elements (he assumed that new elements would be discovered)
• Sometimes he swapped positions of elements if he thought the position better suited their physical properties
• Vertical columns contained elements with increasing relative atomic masses and horizontal rows contained elements with similar chemical properties