Mid 2- Science Exam

What are the most important attempts to classify elements ؟

(G.R) There are many attempts are made by scientists for classification of elements

(G.R) Mendeleev left empty cells in his table

Mendeleev corrected the ................ of some elements which were estimated wrongly

• Atomic number
• Mass number
• Atomic weight

The vertical columns in mendeleev table were known later as ....................

• Groups
• Periods

The horizontal rows in mendeleev table were known later as ................

• Groups
• Periods

How many the elements that mendeleev put them in his table ?

• 118
• 68
• 67

What are the advantages of Mendeleev’s table

What are the disadvantagesof mendeleev’s table

Mendeleev classified the elements of each main group into ........... sub groups

• two
• three
• four