27/13AL+? ->> 24/11NA+4/2HE

 ¹₀n

Explanation:

The given expression is:

          ²⁷₁₃Al      +     ₐᵇT   →   ²⁴₁₁Na    +    ⁴₂He

This expression is typical of nuclear reactions. To balance this expression we must conserved the mass number and the atomic number.

The mass number is the superscripts and the atomic number is the subscript;

 Now;

 conserving mass number:

             27 + b  = 24 + 4

             27 + b  = 28  

                   b  = 28 - 27  = 1

conserving the atomic number;

            13 + a  = 11 + 2

             13 + a  = 13

                    a  = 0

So;

The particle T is a neutron    ¹₀n

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.