To understand what is happening in the reactions of sodium in water and potassium in water, go back to the structure of an atom.
This is a simple diagram showing the parts of the atom. An atom has protons and neutrons in the nucleus with electrons outside the nucleus. Recall that the electrons do not follow distinct paths, but rather are in orbitals. An orbital is a region of space where an electron is likely to be found.
The position of the electrons around the atom cannot be known exactly, but the probable location of the electrons can be shown by writing the electron configurations of an atom. The electron configuration shows the energy level, the subshell, and the orbitals that electrons are most likely in. For example:
The electron configuration for sodium is 1s22s22p63s1. What does this tell us about how the sodium’s electrons are arranged into energy levels, subshells, and orbitals?
This means that sodium has two electrons in the s orbital of the first energy level, two in the s orbital of the second energy level, as well as six in the p subshell of the second energy level. Sodium also has one electron in the s subshell of the third energy level.
Recall that the valence electrons are the electrons that are in an atom’s outermost or highest-occupied energy level. You can determine the number of valence electrons an element has by writing its electron configuration. For example:
The electron configuration for sodium is 1s22s22p63s1. How many valence electrons does sodium have?
The outermost energy level that has electrons in sodium is the third energy level. All electrons in this energy level are valence electrons, so sodium has one valence electron.
The electron configuration for potassium is 1s22s22p63s23p64s1. Answer the question on each slide, based on the valence electron(s) of sodium and potassium.
Reflection
What did you learn about the valence electrons for sodium and potassium?
