Answer:
Sodium and lithium are in the same group of the periodic table; this is because they both have the same number of electrons in their outer shell (1 as indicted by the group number). this commonality is the reason they have similar chemical properties. As we go down the group however, the electronic structure of atoms of an element changes as that there are a increasing numbers of ‘shells’.
Electron ‘shells’ are filled according to ruled of quantum mechanics however to simplify things in this case the first shell can fit 2 electron, the second 8, and the third shell 8. Lithium has 3 electrons, hence it the first shell is filled, and 1 electron occupies the second shell. Whilst Sodium has 11 electrons, hence its first two shells are filled and the third shell is occupied by one electron.
To expand on this question, the duet/octet rule is a rule in quantum mechanics that observes that main group elements tend to be stable with a full outer shell.
This explains why sodium and lithium is found in the form of Li+ and Na+ ions in nature.
Explanation:
