Question

Which of the following species will have the largest and smallest size. Give reason

Mg , Mg2+ , Al , Al3+

Answer 1

Answer

Smallest is Al3+ as cations are always smaller than parent atom,so atom with larger (+)ve nuclear charge will have smallest radius

Largest is Mg as across the period atomic radii decreases.

@rain6342

Answer 2

Answer: Magnesium metal has largest size and aluminium ion has the smallest size.

Explanation:

Atomic radius of an atom is defined as the total distance from the nucleus to the outermost shell of the atom.

As moving from left to right in a period, more and more electrons get add up in the same shell and the attraction between the last electron and nucleus increases, which results in the shrinkage of size of an atom. Thus, atomic radii decreases as we move across a period.

An ion is formed when a neutral atom looses or gains electrons.

• When an atom looses electrons, it results in the formation of positive ion known as cation.
• When an atom gains electrons, it results in the formation of negative ion known as anion.

The size of the cation is small then their neutral atom because it has less electrons while its nuclear charge remains the same. So, the nucleus attracts the electron more towards itself and leads to the decrease in size.

Aluminium is small than magnesium.

So, the order of atomic radii in decreasing order follows:

$Mg>Mg^{2+}>Al>Al^{3+}$

Hence, magnesium metal has largest size and aluminium ion has the smallest size.