Chapter 15, Problem 3TC

(a)

To determine

The rank from smallest to largest, in order of the size of: Hydrogen H, Aluminium Al, Argon Ar.

Answer to Problem 3TC

The order from smallest to largest in order of their size is: H<Ar<Al.

Explanation of Solution

Aluminium is placed in second period and third group of the periodic table. Its atomic number is 13, and the number of shells that occupy these electrons is 3. The last shell contains 3 electrons.

Argon is placed in second period and eighth group in the periodic table. The atomic number that is the number of protons, in Argon is 18 and these are equal to the number of electrons. The number of shells that occupy these electrons is 3.

Hydrogen is located in the first period as well as the first group of the periodic table. It contains 1 electron and hence 1 shell occupies that one electron.

The size of the atom depends on the number of shells, electrons, and the electrostatic force of attraction between the nucleus and electrons it occupy. When moved from left to right in the periodic table, the number of electrons is added in the same energy levels and protons are added in the nucleus that increase the nuclear charge and it attracts electrons more strongly. So, from left to right when moved in the periodic table the atomic size decreases. Hence, atomic size of Aluminium is greater than Argon.

Conclusion:

Therefore,the order from smallest to largest in order of their size is: H<Ar<Al.