Final answer:
The order of increasing radius for Mg2+, O2-, F-, and Ne is Mg2+ < Ne < F- < O2-, with the size determined by the balance of electrons and effective nuclear charge. Atomic size decreases across a period and increases down a group, while ionization energy follows an opposite trend.
Step-by-step explanation:
Order of Increasing Atomic Radius and Ionization Energy
To address the student's original question regarding the order of increasing radius for Mg2+, O2-, F-, and Ne, we must consider two key factors in atomic size: the number of electrons and the effective nuclear charge. For isoelectronic species (atoms or ions with the same number of electrons), the number of protons in the nucleus will primarily define the size. The more protons there are, the tighter the electrons will be pulled towards the nucleus, resulting in a smaller ionic radius. Hence, the order of increasing radius for the given species, considering that O2-, F-, Ne, and Mg2+ are isoelectronic, is: Mg2+ < Ne < F- < O2-.
The atomic size trend for rows in the Periodic Table indicates that as we move from left to right across a period, the atomic radius decreases. This is due to the increase in the number of protons, which increases the nuclear charge, pulling electrons closer to the nucleus and thus decreasing the atomic size.
For example, when placing elements such as Sr, Ca, Si, and Cl in order of increasing atomic radius, we note that Si < Cl < Ca < Sr, because atomic size increases as we move down a group and decreases as we move across a period from left to right.
Regarding ionization energy, which is the energy required to remove an electron from an atom in the gaseous state, the trend is that it increases as we move across a period from left to right and decreases as we move down a group. For instance, if asked to rank Na, O, Ca, and Ne in order of increasing ionization energy, we would have Na < Ca < O < Ne.