When drawing a molecule without knowing its shape, the first step is to determine the connectivity of the atoms, also known as the molecular skeleton or framework. This involves identifying which atoms are bonded to each other and the types of bonds between them. Here's a general procedure to follow:
Identify the atoms present in the molecule and their elemental symbols (e.g., carbon, hydrogen, oxygen, etc.).
Determine the number of bonds each atom can form based on its valence. For example, carbon typically forms four bonds, oxygen forms two bonds, and hydrogen forms one bond.
Start by drawing the central atom(s) and connect them to the surrounding atoms using single bonds. In some cases, the central atom may be obvious (e.g., carbon in an organic compound), while in other cases, you may need additional information or knowledge about the compound's properties.
Proceed to draw the remaining atoms, connecting them to the central atom(s) or other atoms already drawn, again using single bonds.
Pay attention to the octet rule, which states that many elements tend to form stable arrangements by acquiring eight electrons in their valence shell. This rule applies to most atoms except for hydrogen (which prefers two electrons) and elements in the third period or beyond (which can exceed the octet rule).
After drawing the molecular skeleton, additional information or knowledge is required to determine the shape and arrangement of the atoms in three-dimensional space. This information can be obtained from experimental techniques such as X-ray crystallography or spectroscopy, or through computational methods like molecular modeling or quantum chemical calculations.