Write down the electronic configuration of al3+ how many electrons are present in its outer most shell
The Correct Answer and Explanation is:
Electronic Configuration of Al³⁺
The element Aluminium (Al) has an atomic number of 13, which means a neutral aluminium atom has 13 electrons.
The electronic configuration of a neutral Al atom is:
Al (Z = 13): 1s² 2s² 2p⁶ 3s² 3p¹
When Aluminium loses three electrons to form an Al³⁺ ion, the electrons are removed from the outermost shell (the 3rd shell).
So, we remove:
- First: 3p¹
- Second: 3s²
After removing three electrons, the configuration becomes:
Al³⁺: 1s² 2s² 2p⁶
This is the same configuration as the noble gas Neon (Ne).
How many electrons are present in the outermost shell of Al³⁺?
The outermost shell in Al³⁺ is the second shell (n = 2), which consists of:
- 2s²
- 2p⁶
Total electrons in the outermost shell = 2 + 6 = 8 electrons
Explanation
Aluminium (Al) is a group 13 element with an atomic number of 13. This means it has 13 protons and, in a neutral state, 13 electrons. The arrangement of these electrons in shells and subshells is known as the electronic configuration. For a neutral Al atom, the electrons fill the orbitals in the order of increasing energy: 1s, 2s, 2p, 3s, and 3p. Thus, its configuration is 1s² 2s² 2p⁶ 3s² 3p¹.
When aluminium becomes an ion, it typically forms a +3 charge (Al³⁺) by losing three electrons. This happens because aluminium has three valence electrons (3s² 3p¹), which are relatively easy to remove to achieve a stable electronic structure. Losing these three electrons gives it the configuration of 1s² 2s² 2p⁶, which is the same as the noble gas Neon, making it stable.
In the case of Al³⁺, all electrons from the third shell are lost, so its outermost shell becomes the second shell. The second shell now contains eight electrons (2s² 2p⁶), which is a full shell and very stable — this is known as an octet.
Therefore, in Al³⁺:
- Total electrons = 10
- Outermost shell (n=2) electrons = 8
This loss of electrons and resulting stability explains why aluminium commonly forms the +3 ion. The noble gas configuration in Al³⁺ is highly stable and helps to minimize energy, which is why this ionic form is so prevalent in chemical compounds.
