Describe how the modern periodic table is organized.

The modern periodic table is organized based on atomic number, electron configuration, and recurring chemical properties. Here are the steps describing how it is organized:

1. Atomic Number: Elements in the periodic table are arranged in order of increasing atomic number. The atomic number of an element is the number of protons in the nucleus of an atom. It is unique to each element and defines the identity of an element. For example, Hydrogen has an atomic number of 1, Helium has an atomic number of 2, and so on.

2. Periods and Groups: The periodic table is divided into periods (horizontal rows) and groups (vertical columns). There are seven periods and 18 groups in the periodic table. The period number of an element signifies the highest energy level an electron in that element occupies (in the unexcited state), while the group number (1-18) aligns with the number of electrons in the outermost shell (also known as valence electrons).

3. Blocks: The periodic table is also divided into blocks named s, p, d, and f. The block names indicate the subshell that is being filled with electrons. The s-block includes elements from groups 1 and 2 (including Hydrogen and Helium), the p-block includes groups 13 to 18, the d-block contains the transition metals, and the f-block includes the lanthanides and actinides.

4. Chemical Properties: Elements in the same group have similar chemical properties. This is because they have the same number of valence electrons, which largely determine the chemical behavior of an element. For example, all elements in Group 1 (alkali metals) are highly reactive metals.

5. Metallic and Non-Metallic Properties: On the left side of the periodic table, there are metals which have properties like malleability, ductility, and are good conductors of heat and electricity. On the right side of the table, there are non-metals which have the opposite properties. Between metals and non-metals, there are metalloids which have properties in between metals and non-metals.

In summary, the modern periodic table is a systematic way of organizing elements based on their atomic number, electron configuration, and chemical properties.