Rank these ions according to ionic radius (lowest to highest)
Mg^2+, N^3-, O^2-, Na^+, F^-
can you explain how you got your answer? thanks!
To start off, all of these ions have the same number of electrons. So electronegativity and charges are going to determine ionic radium.
N3- has an overall negative charge of 3. In N3- we have 3 more electrons than protons, and a large negative charge. This is going to cause the electrons to be forced away from the nucleus, in order to 'make room' for the three extra electrons.
Mg2+ has an overall positive charge of 2. This means there will be less electrons compared to the number of protons. The electrons are going to 'go towards' the positively charged nucleus, making the ionic radius of Mg2+ small, compared to the rest of the elements.
Everything in-between follows the same trend.
1) Largest to smallest: N3-, O2-, F-, Na+, Mg2+
2) Largest to smallest: P3-, S2-, Cl-, K+, Ca2+
Note where these elements are on the periodic table. Note that they are isoelectronic; i.e., all have 10 electrons. Arranged by periodic table they would show up as
..................N, O, F,
Na, Mg.......
So which element has the smallest number of protons? That is N(7 protons). The protons in N can not attract those 10 electrons as strongly as any of the others; therefore, N^3- must be the largest and they become smaller as you progress left to right. Does that work out? Yes. Mg has 12 protons and will attract those outside electrons stronger than any other ion listed. Mg2+ will be the smallest.
To rank these ions according to ionic radius, we need to consider the number of protons in the nucleus and the number of electron shells surrounding the nucleus.
Here's the step-by-step breakdown:
1. The ionic radius generally increases down a group in the periodic table. Therefore, we can start by comparing the anions (negative ions).
2. F- has the highest nuclear charge (9 protons) among the anions, which attracts its electrons more strongly, resulting in a smaller size compared to the other anions.
3. O2- has a nuclear charge of 8 protons, which is less than F-. Therefore, O2- has a larger ionic radius than F-.
4. N3- has nuclear charge of 7 protons, which is less than O2-. Hence, N3- has a larger ionic radius than O2-.
5. Now let's compare the cations (positive ions).
6. Na+ has fewer electrons than its neutral atom (Na). Due to the decrease in electron-electron repulsion, Na+ has a smaller ionic radius compared to the neutral atom.
7. Mg2+ has an even smaller ionic radius compared to Na+ because it has lost two electrons, resulting in less electron-electron repulsion.
Therefore, when ranking these ions from lowest to highest ionic radius, we have:
F- < O2- < N3- < Na+ < Mg2+.
To rank the ions according to ionic radius from lowest to highest, we need to consider a few factors.
1. Ions of the same element: In general, as we move from left to right across a period in the periodic table, the atomic radius decreases. Therefore, ions of the same element that have gained or lost electrons will have different ionic radii.
2. Charge on the ion: In general, as the charge on an ion increases, the ionic radius decreases. This is because an increased positive charge attracts more electrons, causing the ion to become smaller.
Now, let's apply these factors to rank the given ions:
1. Na+ (sodium ion): Sodium (Na) is a group 1 element located in the far left of the periodic table. When Na loses its valence electron to form Na+, it becomes smaller. Therefore, Na+ has the largest ionic radius among the given ions.
2. Mg2+ (magnesium ion): Magnesium (Mg) is a group 2 element located to the right of sodium. When Mg loses its two valence electrons to form Mg2+, its ionic radius becomes smaller than that of Na+. Hence, Mg2+ has a smaller ionic radius than Na+.
3. O2- (oxide ion): Oxygen (O) is located in group 16 of the periodic table. When oxygen gains two electrons to form O2-, it becomes larger due to increased electron-electron repulsion. Therefore, O2- has a larger ionic radius than Mg2+.
4. F- (fluoride ion): Fluorine (F) is located in group 17 of the periodic table. When F gains one electron to form F-, its ionic radius becomes larger than that of O2-. Therefore, F- has a larger ionic radius than O2-.
5. N3- (nitride ion): Nitrogen (N) is located in group 15 of the periodic table. When N gains three electrons to form N3-, its ionic radius becomes larger due to increased electron-electron repulsion. Hence, N3- has the largest ionic radius among the given ions.
Therefore, the ranked list of ions from lowest to highest ionic radius is:
Mg2+ < Na+ < O2- < F- < N3-