The Periodic Table: Structure & Classification

Question 1

The periodic table is a list of all known elements arranged in order of

Answer 1

atomic number 1 to 118

Question 2

In addition to this, the elements are arranged in such a way that atoms with the same number of shells are placed together, and atoms with similar electronic configurations in the outer shell are also placed together.

This is achieved as follows:

Answer 2

The elements are arranged in rows and columns.

Elements with one shell are placed in the first row (i.e. H and He)

Elements with two shells are placed in the second row (Li to Ne) and so on.

Question 3

A row of elements thus arranged is called a

Answer 3

period

Question 4

The period number, n, is the

Answer 4

outer energy level that is occupied by electrons.

Question 5

In addition, the elements are aligned vertically (in columns) with other elements in different rows, if they share the same

Answer 5

outer-shell electronic configuration
The outer electrons are known as the valence electrons

Question 6

A column of elements thus arranged is called a

Answer 6

group

Question 7

Since the electronic configurations of H and He are unusual, they do not fit comfortably into any group. They are thus

Answer 7

allocated a group based on similarities in physical and chemical properties with other members of the group

He is placed in group 0 on this basis, but hydrogen does not behave like any other element and so is placed in a group of its own