Question

WhySodium ion, magnesium ion, oxide ion and Neon atom have different atomic number but same electron arrangement of 2, 8.​

Answer 1

Answer:

It has one valence electron in the n=3 energy level. Upon losing that electron, the sodiu ion now has an octet of electrons from the second energy level and a charge of 1+. ... In this case, the magnesium atom loses its two valence electrons in order to achieve the same arrangement as the noble gas neon and a charge of 2+.

Answer 2

The number of electrons originally in Sodium, Magnesium, Oxygen, and Neon are 11, 12, 8, and 10 respectively. Thus, they have different atomic numbers. But to stabilize and form ions, all of them get to a 2-orbit stable configuration of "2, 8".

Electronic Configuration of Elements :

• The electron configuration of an element describes the distribution of electrons of that element.
• It denotes the number of electrons, the number of shells, and the presence of electrons in each shell.
• The electron orbits follow a standard rule on electron capacity and distribution.
• The sequence of a number of maximum electrons in a shell from orbit number 1, 2, ... is called the Magic Number series.
• Magic Number series for electron distribution: 2, 8, 8, 18, 18, 32..

Sodium and its ion : $(Na^{+})$

• Number of electrons in sodium : $Z = 11$
• Electronic configuration of sodium : $2,8,1$
• The last electron tends to remove to get a stable 2-orbit-filled form of sodium ion. So, the sodium ion configuration is : $2,8$

Magnesium and its ion : $(Mg^{2+})$

• Number of electrons in magnesium : $Z = 12$
• Electronic configuration of magnesium : $2,8,2$
• The last 2 electron tends to remove to get a stable 2-orbit-filled form of magnesium ion. So, the ion configuration is : $2,8$

Oxide and its ion : $(O^{2-})$

• Number of electrons in oxygen : $Z = 8$
• Electronic configuration of oxygen : $2,6$
• The oxygen ion gains 2 electrons to fill its outer orbit and get stable. So, the oxygen ion configuration is : $2,8$

Neon :

• Number of electrons in Neon : $Z = 10$
• Electronic configuration of Neon : $2,8$
• The Neon already has its outer orbit filled. So it involves no gain or loss of electrons to form any ion.

Hence, all the given elements have a different number of electrons and thus different atomic numbers, But their ions get stabilized to the same electronic configuration.

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