Attempts of elements classification

Question 1

Who created the first real periodic table ?

Answer 1

Mendeleev.

Question 2

How many elements were known in Mendeleev’s time ?

Answer 2

67 elements.

Question 3

How did Mendeleev arrange the elements ?

Answer 3

he arranged each element on cards in ascending order according to their atomic weights and important properties from left to right in horizontal rows.

Question 4

What’s the definition of groups in the periodic table ?

Answer 4

vertical columns of elements with similar properties.

Question 5

Why did Mendeleev classify the elements of each main group into two subgroups ( A & B ) ?

Answer 5

due to the differences between their properties.

Question 6

In Mendeleev’s periodic table, what way did the atomic weights of elements increase ?

Answer 6

it increased in a non-uniform way from left to right in horizontal rows.

Question 7

What repeats periodically by the beginning of each new period ?

Answer 7

the properties of elements.

Question 8

Why did Mendeleev leave gaps in his periodic table ?

Answer 8

he was predicting the discovery of new elements.

Question 9

What are the advantages of Mendeleev’s periodic table ?

Answer 9

1. he left gaps in his periodic table.

2. he corrected the atomic weights of some elements which were estimated wrongly.

Question 10

What’s the name of Mendeleev’s book ?

Answer 10

“Principles of chemistry”.

Question 11

What are the disadvantages of Mendeleev’s periodic table ?

Answer 11

1. He had to make a disturbance in the ascending order of the atomic weights of some elements to put them in groups that suited their properties.
2. He had to deal with isotopes of one element as different elements due to the difference in their atomic weights.

Question 12

Which scientist discovered that the periodicity properties of elements are related to their atomic numbers not their atomic weights ?

Answer 12

Moseley.

Question 13

Who discovered that the nucleus contains positively charged protons ?

Answer 13

The New Zealand scientist Rutherford .

Question 14

How did Moseley arrange the elements in his periodic table ?

Answer 14

He arranged them in ascending order according to their atomic numbers, where the atomic number of each element increases by one from the preceding element in the same period.

Question 15

What is the zero group ?

Answer 15

It’s the group which includes the noble (inert) gases to the table.

Question 16

What is the place below the table for in Moseley’s periodic table ?

Answer 16

It’s for lanthanides and actinides elements.

Question 17

What did the Danish scientist Bohr discover ?

Answer 17

He discovered the main energy levels of the atom and their number reaches 7 in the heaviest atoms known till now.

Question 18

What are energy sublevels ?

Answer 18

They are a definite number of levels that each main level contains.

Question 19

How are elements classified in the modern periodic table ?

Answer 19

They are classified in ascending order according to their atomic numbers, the way of filling energy sublevels with electrons.

Question 20

How many elements are there in the modern periodic table ?

Answer 20

118 elements, 92 elements are abundant in the earth’s crust while the rest are prepared artificially.

Question 21

What does the modern periodic table consist of ?

Answer 21

7 horizontal periods, 18 vertical groups while the elements are classified into 4 blocks.

Question 22

Which block is located on the left side of the periodic table ?

Answer 22

S-block elements.

Question 23

Which groups are s-block arranged in ?

Answer 23

1A and 2A.

Question 24

Where is p-block located in the periodic table ?

Answer 24

On the right side.

Question 25

Which groups are p-block arranged in ?

Answer 25

3A to 7A and group zero (6 groups).

Question 26

Where is d-block located ?

Answer 26

In the middle of the periodic table.

Question 27

What are d-block elements known as ?

Answer 27

Transition elements.

Question 28

What groups is d-block arranged in ?

Answer 28

3B to 7B and group 8 and group 1B and 2B (eight groups).

Question 29

What does group 8 consist of ?

Answer 29

It consists of three vertical columns.

Question 30

Where is f-block located ?

Answer 30

It is located under the periodic table.

Question 31

What does the f-block elements include ?

Answer 31

Lanthanides and actinides.

Question 32

What are elements in the same group similar in ?

Answer 32

They are similar in the number of electrons in the outermost energy level, so they are similar in their chemical properties.

Question 33

What are elements in the same group different in ?

Answer 33

They are different in the number of energy levels occupied by electrons.