The electronic configuration of the element which is just below it will be 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p³...so it's atomic number= 33.

Electronic Configuration and Periodic Table

- The electronic configuration of an element represents the arrangement of electrons in its atoms.
- The electronic configuration is written in the order of increasing energy levels or shells and subshells.
- The periodic table is a tabular arrangement of elements based on their electronic configurations and chemical properties.
- Elements with similar electronic configurations and chemical properties are placed in the same group or column.
- Elements with increasing atomic numbers are placed in the same period or row.

Given Information

- The electronic configuration of an element is 1s2 2s2 2p6 3s2 3p3.
- The element has 16 electrons (2+2+6+2+3=15) and its highest energy level is 3.

Solution

- The last three electrons of the element occupy the 3p subshell, which can hold a maximum of six electrons.
- Therefore, the next element in the periodic table, which has one more electron than the given element, would have the electronic configuration 1s2 2s2 2p6 3s2 3p4.
- The atomic number of an element corresponds to the number of protons in its nucleus, which is also equal to the number of electrons in its neutral atoms.
- The given element has 16 electrons, so its atomic number is 16.
- The next element in the periodic table, with one more electron, has an atomic number of 17.
- Therefore, the element just below the given element in the periodic table has an atomic number of 16 - 1 = 15.
- The element with atomic number 15 is phosphorus (P).
- Hence, the correct answer is option A (33), which is not relevant to the given information and is probably a distractor.

Note: It is important to understand the periodic table and the trends in the properties of elements, such as atomic radius, ionization energy, electronegativity, and chemical reactivity, based on their electronic configurations.