Unit one less. 1-2 2nd Perp.

Transition elements appear starting from period …………

• 2

• 4

• 3

• 1

Burning of carbon in air produces ………..

• CO₂

• CuO

• HCl

• c

The number of energy levels in the heaviest known atom is ........ levels.

• 8

• 9

• 4

• 7

The number of elements in Mendeleev's table is …………..

• 118

• 67

• 92

• 26

The atomic number of the element which lies in period (4) and group (2A) is …...

• 20

• 12

• 22

• 2

Each period in the modern periodic table starts with……….

• nonmetal

• inert gas.

• metalloid

• metal

From the advantages of Mendeleev's table is that he ..…

• Corrected the atomic weights of some elements.

• Put lanthanides and actinides in special place.

• Arranged the elements in an ascending order according to their atomic numbers.

• Classified the table into four blocks.

Sodium reacts with water and……….gas is evolved.

• N₂

• O₂

• CO₂

• H₂

The modern periodic table is composed of ……..

• 17 group and 8 periods.

• 8 groups and 18 periods.

• 18 groups and 7 periods.

• 7 groups and 17 periods.

The scientist who discovered the main energy levels is…………..

• Bohr

• Mendeleev

• Moseley

• Rutherford