The magnetic moment of an atom can be determined by the number of unpaired electrons in its electron configuration. In this case, the atom has a magnetic moment of 3.73 BM, which indicates the presence of unpaired electrons.

To find the atomic number of the element just below it in the periodic table, we need to first determine the atomic number of the given atom. Since the atomic number of an element represents the number of protons in its nucleus, it also determines the position of the element in the periodic table.

To find the atomic number, we need to consider the range provided, which is between 22 and 30. This range corresponds to the elements titanium (Ti) with atomic number 22 and zinc (Zn) with atomic number 30.

Since the given atom has a magnetic moment, it must have unpaired electrons, which means it is not a noble gas. Noble gases have completely filled electron configurations and do not exhibit magnetic moments.

The element with atomic number 29, which is copper (Cu), is just below the given atom in the periodic table. Copper has an atomic number between 22 and 30 and has a magnetic moment of 3.73 BM.

Now, let's determine the group, block, and period of the former element.

- Group: The group number of an element represents the number of valence electrons it has. Valence electrons are the electrons in the outermost energy level of an atom. To determine the group number, we need to look at the electron configuration of the element just below the given atom.

Copper (Cu) has an electron configuration of [Ar] 3d10 4s1. The valence electron of copper is in the 4s orbital, so it belongs to Group 11.

- Block: The block of an element is determined by the type of orbital in which the valence electron is located. Copper (Cu) has its valence electron in the 4s orbital, which belongs to the s-block.

- Period: The period number of an element represents the highest principal energy level occupied by electrons. Copper (Cu) has its valence electron in the 4s orbital, so it belongs to Period 4.

To summarize:
- The atomic number of the element just below the given atom is 29, which corresponds to copper (Cu).
- Copper belongs to Group 11, the s-block, and Period 4.