# Chem

Define isoelectronic series. Put the K+, Ca2+, Cl-, and Ar ions and atoms in order of increasing size and explain the trends.
Count the number of electrons for each atom
Then, explain the (column) size trend for Mg2+ versus Ca2+ ions

Is the order cl k ca Ar? How would you count electrons? What would the size trend be?

1. 👍
2. 👎
3. 👁
1. I looked up the neutral atom and ionic species and this is what I found from smallest to largest. It isn't what I expected.
Ar < Cl^- < Ca^2+ < K^+

I thought in an isoelectronic series (which this is since all atoms/ions have 18 electrons) that Cl^- would be larger than Ar because you are adding an extra electron to make the -1 ion, the electrons repel each other, and that makes the size larger. On that basis then, Ar, the next element after Cl will be slightly smaller because there is an extra + charge in the nucleus (18 vs 17) and that pulls the outside electrons in a little more. So far so good. That makes sense and is true. Ar is slightly smaller than Cl^-. Then my reasoning goes that the K^+ should be slightly smaller than Ar because the same number of electrons are there and there is one more proton in the nucleus. That should pull the electrons in more and the trend to Ca^2+ should continue BUT that doesn't fit the data.
That is the trend for O^2-, F^-, Ne, Na^+, Mg^2+. I don't know why it isn't the trend in your series.
Here is a site showing the trend in decreasing size for an isoelectronic group. Scroll down part way to see the diagram. http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/Periodic_Trends_of_Elemental_Properties/Periodic_Trends_in_Ionic_Radii

Here is the site where I picked up the atom/ion sizes. Scroll to almost the bottom of the page.

1. 👍
2. 👎

## Similar Questions

1. ### Chemistry

what happens when NaCl(s) is dissolved in water? (1)Cl-ions are attracted to the oxygen atoms of the water (2)Cl-ions are attracted to the hydrogen atoms of the water. (3)Na+ions are attracted to the hydrogen atoms of the water.

2. ### Chemistry

A covalent bond forms when (1)two nuclei share electrons in order to achieve a complete octet of electrons (2) atoms form ions and then electrostatic forces of attraction bond the ions together. (3)repulsive forces between atoms

3. ### Chemistry

How does table salt (NaCl) dissolve in water? A. The oxygen atoms in water molecules attract sodium ions. B. Each sodium ion is surrounded by chloride ions. C. Each NaCl molecule is surrounded by water molecules. D. Water

4. ### chemistry

what is the mass in grams? a) 3.011 x 10^23 atoms F b)1.50 x 10^23 atoms Mg c)4.50 x 10^12 atoms Cl d)8.42 x 10^18 atoms Br e) 25 atoms w f) 1 atom Au can you please explain a and b to me then i'll come back later and see if i did

1. ### Chemistry

1) What is the charge on the ion that Selenium forms in an ionic compound? I am not sure about this. 2) What noble gas is isoelectronic with this ion. I was thinking Krypton because it is a noble gas and it is the closest to

2. ### CHEM

For a molecule of fluorous acid, the atoms are arranged as HOFO. What is the formal charge on each of the atoms? Enter the formal charges in the same order as the atoms are listed. For this question I tried entering: +1,-2,+3,-2

3. ### chemistry need help

Determine the number of moles of each specified atom or ion in the given samples of the following compounds.( Hint: the formula tells you how many atoms or ions are in each molecule of formula unit.) a. O atom in 3.161x10^21

4. ### Science

Which factor impacts the possible number of ways in which different atoms can be put together? An atoms inability to share neutrons and protons. The ability of atoms to combine in unlimited ways. An atoms inability to react with

1. ### Chemistry

A solution contains 0.0500 M Ca2 (aq) and 0.0350 M Ag (aq). What will be the concentration of Ca2 (aq) when Ag2SO4(s) begins to precipitate? What percentage of the Ca2 (aq) can be separated from the Ag (aq) by selective

2. ### Chemistry - Periodic Trends

For the isoelectronic series S2-, Cl-, Ar, K+, and Sc3+, which species requires the least energy to remove an outer electron? thanks They all have the same number of electrons (40) in the same shell arrangements, but S(2-) has the

3. ### Chem

How do you figure out the Noble Gas Configuration? Also, why do you not put in the "p" level and when do you( if you even do) put it in? You need to be more specific about your question. Elements that lose electrons (Na, Ca, Al,

4. ### Chemistry

Pure water and Sodium chloride are both poor conductors of electricity by themselves. However, if sodium chloride crystals are dissolved into the water the solution becomes a good conductor of electricity. How does this phenomenon