Account for the fact that the line that separates the metals from the nonmetals on the periodic table is diagonal downward to the right instead of horizontal or vertical.

The periodic table organizes elements based on their atomic number and electron configurations, which in turn helps us understand their atomic properties and general chemical behavior. Elements placed in the same group (vertical column) generally have similar properties due to their similar electron configurations.

The periodic table consists of metals, nonmetals, and metalloids. Metals are typically found on the left-hand side, while nonmetals are on the right-hand side. In general, metals are shiny, ductile, malleable, and have high thermal and electrical conductivity. Nonmetals, on the other hand, are generally dull in appearance, brittle, and have lower thermal and electrical conductivity. Metalloids exhibit properties between those of metals and nonmetals.

Electron configurations of elements play a vital role in determining their atomic properties and positioning in the periodic table. As we move across a period from left to right, elements face an increase in effective nuclear charge and a decrease in atomic radius. These periodic trends result in an increase in ionization energy, electron affinity, and electronegativity from left to right across the periodic table.

The separation between metals and nonmetals in the periodic table is not a straight horizontal or vertical line; instead, it's a diagonal line that moves downward from right to left. This diagonal separation occurs due to the periodic trends mentioned earlier. As we move across a period, the change in properties of elements doesn't occur abruptly. Instead, there is a gradual change in the atomic properties due to variations in electron configuration, atomic radius, and effective nuclear charge. These gradual changes lead to the formation of metalloids, which exhibit properties between those of metals and nonmetals. The metalloids occupy the space between metals and nonmetals, forming the diagonal separation line. In conclusion, the diagonal downward separation of metals and nonmetals in the periodic table is due to the gradual change in atomic properties as we move across the periodic table. This change occurs because of variations in electron configurations, effective nuclear charge, and atomic radius, resulting in periodic trends that differentiate metals, nonmetals, and metalloids.