Using only the periodic table, predict the most stable ion for Na, Mg. Al, S, Cl, K, Ca, and Ga.

Using only the periodic table, predict the most stable ion...

Key Concepts

Comparison with Empirical Data

While the periodic table offers strong predictive power concerning ion formation and trends in ionic radii, empirical data such as that presented in figures or measured radii can exhibit deviations due to factors like coordination effects and experimental conditions. Comparing predictions based solely on periodic trends with empirical results helps validate the model and highlights any nuances that must be considered in real-world applications.

Isoelectronic Series and Comparative Ionic Sizes

Many ions formed by different elements can end up having the same number of electrons, leading to an isoelectronic series. Within such a series, the ionic radius is primarily determined by the number of protons in the nucleus; more protons mean a greater effective nuclear charge and, therefore, a smaller radius. This concept allows us to rationalize and arrange ions from largest to smallest based on their corresponding nuclear charges.

Ion Stability Prediction

This concept involves using an element's position on the periodic table to predict which ion it will most likely form based on achieving a noble gas electron configuration. Typically, elements will lose or gain electrons to obtain a full valence shell. For example, metals in groups 1 and 2 tend to lose electrons to form cations, while nonmetals in groups 16 and 17 tend to gain electrons to form anions. This approach relies on the octet rule and the general periodic trends in electron configuration.

Periodic Trends in Ionic Radii

The periodic table provides guidance on how atomic and ionic sizes change across periods and down groups. Generally, moving across a period leads to a decrease in atomic radius due to increasing effective nuclear charge, whereas moving down a group increases the radius due to the addition of electron shells. When ions are formed, the loss or gain of electrons will also modify ionic sizes, making it possible to predict relative radii based solely on an element’s position.

Effective Nuclear Charge

Effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom. It plays a crucial role in determining both atomic and ionic sizes. In a series of ions that are isoelectronic, a higher effective nuclear charge will pull the electrons closer to the nucleus and result in a smaller ionic radius. Conversely, a lower effective nuclear charge means less pull on the electrons and a larger ionic radius.

Transcript

00:01 All right, in this question, we are predicting the most stable ion for a number of atoms.

00:09 And we'll start with sodium.

00:13 So sodium is in group 1a of the periodic table.

00:18 Now, the key about this question is that all of the 1a atoms like to lose their electrons.

00:30 They like to lose their electrons so they can adopt a normal gas configuration and satisfy the act -ut rule.

00:36 We'll use sodium as an example.

00:38 It has one valence electron because it's in group 1a.

00:43 But if it loses that electron, they'll have the configuration of neon.

00:48 Because in current state, if you write the configuration of sodium, it's got one electron in the s orbital, it's easier for it to just lose that electron to form a stable octet.

01:04 So, sodium is going to form an a plus because it wants to lose one electron.

01:17 And let's trade that out.

01:24 Okay.

01:25 Next up we have magnesium.

01:27 Magnesium is over here.

01:29 It's in row 2a, or column 2a.

01:32 So it's got two valence electrons, and so it'll form mg 2 plus.

01:39 Because if it gets rid of its two electrons, i'll have the configuration of neon and it'll be stable.

01:46 So as a general rule, all items in row two, at column two of the periodic table, like to lose two electrons and form a two plus ion.

01:59 Now aluminum over here, aluminum is in group 3a, so it's got three valence electrons, and it will prefer.

02:08 To lose those three electrons to form a full octet.

02:13 Because the other possibility for it is to gain five electrons.

02:17 It's easier for it to lose three than gain five.

02:20 So aluminum will show up as 3 plus...

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