Question

How many periods of the periodic table have 8 elements, how many have 18 elements, and how many have 32 elements?

Short answer

2 periods have 8 elements, 2 have 18 elements, and 2 have 32 elements.

Step-by-step solution

Identify Periods with 8 Elements

Observe the first row of the periodic table. The second and third periods each contain 8 elements, starting with Lithium (Li, atomic number 3) to Neon (Ne, atomic number 10) for the second period, and from Sodium (Na, atomic number 11) to Argon (Ar, atomic number 18) for the third period. Hence, there are 2 periods with 8 elements.

Identify Periods with 18 Elements

Next, we examine the fourth and fifth periods of the periodic table. These periods extend from Potassium (K, atomic number 19) to Krypton (Kr, atomic number 36) and from Rubidium (Rb, atomic number 37) to Xenon (Xe, atomic number 54) respectively. Consequently, there are 2 periods with 18 elements.

Identify Periods with 32 Elements

Finally, consider the sixth and seventh periods. The sixth period ranges from Cesium (Cs, atomic number 55) to Radon (Rn, atomic number 86) and includes the Lanthanides. Similarly, the seventh period extends from Francium (Fr, atomic number 87) to Oganesson (Og, atomic number 118), inclusive of the Actinides. Therefore, there are 2 periods with 32 elements.

Key concepts

Chemical Elements

Chemical elements are pure substances consisting of only one type of atom. Each element is distinguished by its unique set of properties and its atomic structure. In the periodic table, the elements are systematically organized based on these characteristics.
One of the most recognizable features of an element is its symbol, often derived from its English or Latin name. For example, the symbol for Hydrogen is H, and for Gold, it is Au from its Latin name Aurum.

• Over 100 known elements exist, with some occurring naturally and others being synthesized in laboratories.
• Each element has a unique placement on the periodic table, which helps scientists predict its behavior and properties.

Understanding the concept of chemical elements is essential for exploring more complex topics in chemistry, such as reactions, compounds, and the structure of the matter itself.

Atomic Number

The atomic number is a fundamental property of a chemical element. It represents the number of protons found in the nucleus of an atom of the element. This number not only defines the identity of the element but also determines its place in the periodic table.
For instance, the atomic number of Carbon is 6, indicating that each carbon atom has six protons. The atomic number is more than an identifier; it is a crucial indicator of the element’s chemical behavior.

• Elements are ordered in the periodic table by increasing atomic number.
• Protons have a positive charge, balancing out the negatively charged electrons surrounding the nucleus.

The atomic number is essential for distinguishing elements from one another, even if they share similar chemical properties or appear near each other on the table.

Periods

Periods are the horizontal rows of the periodic table. There are seven periods in total, and they represent elements with an increasing number of electrons filling their atomic orbitals. Each row signifies the number of electron shells present in the atoms of the elements.

• The first period starts with Hydrogen and Helium, having only two elements because the first electron shell can hold a maximum of two electrons.
• As we move down the table, periods consist of more elements due to additional electron shells being filled.
• The most extended periods are the sixth and seventh, which include 32 elements each.

Understanding periods is key to grasping why elements in the same period display progressive changes in chemical properties from left to right. This is due to the additional electrons, which affect atomic size and reactivity.

Group of Elements

Groups are the vertical columns of the periodic table, often referred to as families. Elements within the same group have similar chemical properties because of their analogous outer electron configurations.

• Each group is identified by a number, running from 1 to 18.
• For example, the noble gases, known for being inert, make up Group 18.
• Group elements react similarly in chemical reactions due to equivalent valence electron counts.

Learning about element groups helps predict how different elements might react under certain conditions. It also aids in understanding the periodic trends, such as electronegativity and ionization energy, which tend to exhibit certain patterns within a group.