Question

How does knowing the electronic structure of an atom aid chemists in predicting chemical reations

Answer 1

The electron configuration allows us to know how many valence electrons are available. Valence electrons are what allow chemical reactions to take place.

Answer 2

depending on number of electrons in the last shell chemists can predict whether chemical reaction can or cannot take place i believe.

Answer 3

Generally speaking, all atoms will look to obtain the electronic configuration of a Noble gas element (i.e. the elements in Group 8 of the periodic table; Helium, Neon, Argon,....). All of these elements have a full outer shell of electrons, making them very stable. So, if we were to look at the reaction of atoms of elements, we could say whether they were going to the able to bond by looking at the number of electrons an atom needs to gain/lose/share, and whether there is an other atom present which is in a favorable position to gain/lose/share electrons with it also.

An example of this is when one atom takes electrons off another atom which leads both to having a full outer shell of electrons. Take, for example, the reaction of sodium (Na) and chlorine (Cl). Sodium is a Group 1 element, meaning that it has one electron in its outer shell. So, it would be most favorable for it to react in such a way as to lose this electron, so that that shell becomes empty and the full shell of electrons below that now acts as the outer shell.

Chlorine is a Group 7 element, meaning it has 7 electrons in its outer shell. To complete a full outer shell of 8 electrons, it would like to gain one electron to obtain a more stable electronic configuration. Hence, an atom of sodium can give its negatively charged electron away (becoming a positively charged ion or cation) to an atom of chlorine, which becomes a negatively charged ion or anion, as it has gained a negatively charged species. Hence, the two oppositely charged ions are electrostatically attracted to each other to form an ionic bond of NaCl, or Sodium Chloride, as it is known.

We couldn't have predicted this without knowing the electronic configuration of both elements, and that they would exhibit this chemical behavior in bonding to each other. The same goes of the formation of covalent bonds, where electrons are shared between atoms rather than being completely transferred from one to another, with the same general target of obtaining full outer shells of electrons. We can also use it to work out the number of atoms of each element we need to be involved in taking/giving/sharing electrons, as more than one of a certain type may be required depending on how many electrons it is favorable for that single atom to take/give/share (e.g. In water, H2O, we require 2 hydrogen atoms to each share their 1 electron with oxygen for all to complete a full outer shell of electrons). Hope that helps! :)
http://www.uamont.edu/facultyweb/fawley/Principles%20of%20BiologyI/ch2b-outline.pdf