Question

a. How many groups are in the periodic table? b. How many periods are in the periodic table? c. Which two blocks of the periodic table make up the main-group elements?

Short answer

a. 18 groups. b. 7 periods. c. s and p blocks.

Step-by-step solution

Determine the number of groups

The periodic table is divided into columns called groups. These columns represent elements with similar properties. Count the number of these vertical columns.

Count the number of periods

The rows of the periodic table are called periods. Each period corresponds to a different principal energy level of electrons. Count the number of these horizontal rows.

Identify the main-group elements

The main-group elements are found in two specific blocks of the periodic table: the 's' block and the 'p' block. These blocks include the groups ranging from 1 to 2 and 13 to 18. Note which blocks make up these groups.

Key concepts

Groups in the Periodic Table

The periodic table is one of the most important tools in chemistry. It helps us organize and understand the elements. One way the periodic table is organized is by grouping elements into columns called groups.
Groups are vertical columns and each group contains elements with similar chemical properties. These properties are determined by the number of valence electrons in the outermost shell of the atoms.
There are 18 groups in the periodic table. Elements in the same group often react similarly. For example, the elements in Group 1 are known as alkali metals, and they are very reactive with water.

• The first group has elements like hydrogen and lithium.
• The second group has elements like beryllium and magnesium.
• Groups 13 to 18 are also known as the main-group elements.

Understanding groups helps you predict how elements will interact in chemical reactions.

Periods in the Periodic Table

The periodic table also organizes elements into horizontal rows called periods.
Each period represents a different principal energy level of electrons in atoms. As you move from left to right across a period, the atomic number increases, and elements have one more proton and one more electron than the element before it.
There are 7 periods in the periodic table. Elements in the same period do not necessarily have similar properties, but they do have the same number of atomic orbitals.

• Period 1 has two elements: hydrogen and helium.
• Period 2 includes elements like lithium and beryllium.
• Period 7 includes many of the heavy and radioactive elements.

Recalling the number of periods and understanding their significance can help you track how elements gain complexity and change in reactivity across the table.

Main-Group Elements

The main-group elements are a crucial part of the periodic table. These elements are found in two specific blocks: the 's' block and the 'p' block.
The 's' block includes Groups 1 and 2. These are the alkali metals and alkaline earth metals, respectively. They have their valence electrons in the s orbital.
The 'p' block includes Groups 13 to 18. These groups contain elements like boron, carbon, nitrogen, oxygen, and halogens. They have their valence electrons in the p orbital.

• The main-group elements include both metals and nonmetals.
• These elements play an essential role in life's chemistry and many industrial processes.
• Main-group elements are critical in forming compounds like salts and organic molecules.

By understanding the main-group elements, you can better predict physical and chemical properties, as well as how elements will bond with others.