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Valence electrons are the electrons located in the outermost shell of an atom. They are crucial in determining how an element will interact with others to form compounds. In simple terms, think of them as the 'hand-shakers'—they are the ones who reach out, make bonds, and form relationships with other atoms.

For instance, in our exercise, we calculate the total number of valence electrons in electrons in \(\mathrm{SbCl}_{5}\) to determine how the atoms can bond together. Antimony (Sb) has 5 valence electrons being a member of group 15, and chlorine (Cl) has 7, as it's part of group 17. Knowing the count of valence electrons is the starting point for drawing Lewis structures, which visually represent the arrangement of electrons in a molecule.

The octet rule is a chemical axiom that reflects a pattern of chemical bonding and stability in molecules. It states that atoms tend to bond in such a way that each atom has eight electrons in its valence shell, giving it the same electronic configuration as a noble gas.

The rule is based on the observation that elements are particularly stable when surrounded by eight electrons. This rule is a handy guideline for understanding the distribution of electrons in most molecules. However, there are exceptions, particularly with elements beyond the second period of the periodic table that can have more than eight electrons, known as an expanded octet. This is evident in our exercise example, \(\mathrm{SbCl}_{5}\), where the central antimony atom doesn't adhere to the standard octet rule and instead forms an expanded octet.

Electron distribution refers to how electrons are allocated around an atom or within a molecule. The Lewis structure is a crucial tool for visualizing this distribution, as it shows how the valence electrons are shared between atoms to form bonds. Electrons are typically paired, and in simple molecules, they are distributed to satisfy the octet rule for each atom.

In distributing electrons, we often start by pairing them on the outer atoms until they fulfill their octet, then place any remaining electrons around the central atom. In molecules like \(\mathrm{SbCl}_{5}\), the number of valence electrons exceeds what is needed to complete an octet for the central atom, which leads to electron distribution beyond the octet rule. A clear understanding of electron distribution is key to mastering the intricacies of chemical structures and reactions.