Ions represent elements that possess either a positive charge or a negative charge.
Determining Ionic Charge
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concept
Ions Concept 1
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At this point, we've just examined atoms where we're dealing with the neutral element that has the same number of protons and electrons. Now when the number of protons and electrons are different, that's when we go into ions. Ions themselves are created from the loss or gaining of electrons by elements. So in the creation of an ion or either losing electrons or gaining electrons, we're gonna say here when an element loses electrons, it becomes a positively charged ion called a cation. Now this makes sense. You're losing negatively charged electrons. If I'm losing something negative, I'm becoming more positive. Now on the other end, when an element gains electrons, so it's gaining negative electrons, It becomes a negatively charged ion called an anion. So just remember, cations are positively charged ions anions are negatively charged ions. We're gonna say here a new term, isoelectronic. This is when elements have the same number of electrons. So just remember, the difference between atoms and ions is that atoms have the same number of protons and electrons, but when we become an ion, we've either lost electrons or gained electrons. This causes a difference in the number of protons and electrons within a given element. So keep that in mind when dealing with ions.
Ions are formed from either the loss or gaining of electrons by a neutral element.
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Ions Concept 2
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Now let's see exactly how these positive ions and negative ions come about. If we take a look at the first one, we have a representation of an atom here. Here we have 11 over 5 and then b. Remember, 11 represents our mass number, which is just the number of protons and neutrons together. On the bottom, we have our atomic number, which represents the number of just protons. How do we know our atomic number is 5? If we look at the model of the atom here, we have 1, 2, 3, 4, 5 for the number of protons. If we're to look on the periodic table, we'd see that the only element on the periodic table with an atomic number 5 would have to be boron. That's why the letter here is b. Now what we need to realize next is how many electrons do we have within this atom? Well, we have 5 electrons because we have 1, 2, 3, 4, and 5, 5 electrons. So we have here are 5 protons, and we have here 5 electrons. Okay? They're equal to one another. And if you were to think about it, 5 protons, each one having a charge of plus 1, would mean that this is plus 5. Five electrons each with a negative one charge would mean that this is negative 5. If you add plus 5 and negative negative 5 together, they totally cancel one another out, so you'd have a number of 0. That means that this representation of boron is neutral, so this is the boron atom. If we go to the other image of boron, notice that we have here this first circle. Right? This first circle here has 2 electrons in it, and then we have this second circle here, which has 3 electrons in it. But in the other picture of boron, the second circle is now gone. Those 3 electrons are no longer there. All we're left with is 2 remaining electrons. So if we look, the number of protons within the nucleus hasn't changed. It's still 1, 2, 3, 4, 5. So we still have 5 protons, but now we only have 1, 2 electrons. If we think about it, this would be plus 5, plus, minus 2. Right? Because of the 2 electrons. When you add those together, you'd have plus 3 as your answer. So we have a charge of plus 3, or you can write it as 3 plus. So talk to your professor. Some professors don't care if it's written as plus 3 or 3 plus. Traditionally, we write the number before the charge, but it really doesn't matter. Now here, because it has a charge of plus 3 or 3 plus, it represents an ion. Remember, an ion will have a charge because it's either lost or gained electrons. In this case, it's lost 3 electrons so it becomes plus 3. So this represents our boron ion. If we take a look at, the next part with the anions, we have here oxygen. Oxygen's elemental symbol is o. We see here that it has an atomic number of 8, so it has 8 protons, and then here its mass number is 6, so that means it's gonna represent protons and neutrons together. So we know that this oxygen has 8 protons. Let's count the number of electrons. So we have 1, 2, 3, 4, 5, 6, 7, 8. It has 8 electrons. So these numbers are equal to one another. So if we did plus 8 +-8, that would give us 0 at the end. So this is our oxygen atom. Now what's the difference between this representation of oxygen and the other one? Well, you should notice that the outer circle had originally 6 electrons on it, but now we've gained 2 additional electrons. So now there's 8 electrons on the outside. Now the number of protons, of course, is not changing because, remember, to create an ion, you're either gaining or losing electrons. The other subatomic particles, protons and neutrons, stay what they are. So here we have 8 protons, and then if you count up all the electrons and add those 2 additional ones, so 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, we have 10 electrons. So that would be plus 8, plus, minus 10 equals negative 2. So the charge here would be minus 2 or 2 minus Again, you can either put the chart before the number or the number before the charge. It really is a case by case basis with professors because some professors really don't care if you write 2 minus for the ion or minus 2. So make sure you you talk to them and make sure which version they want. So here it has a charge so this would be the oxygen ion. So just remember this is what's really going on. When we're losing electrons, we gain a positive charge. When we're accepting or gaining electrons, we gain a negative charge. Now that we know the idea behind ion formation, let's continue on to some questions. Let's see if we can determine what the charges are, how many subatomic particles are present for any given ion.
A positively charged ion is called a cation and a negatively charged ion is called an anion.
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example
Ions Example 1
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So here in this example question, it states, determine the number of protons, neutrons and electrons for the following cation. Now it's a cation because it possesses a positive charge, that positive charge being 3 plus. Now, when looking at the other numbers, we know that this 13 here represents our atomic number, which uses the variable z. Remember, the atomic number gives us the number of protons, and because it's 13, that means we have 13 protons. That means that option d cannot be an answer because here we do not have 27 protons. Next, we have the number above the 13 and 27. Remember, that is your mass number, which uses the variable a. Your mass number gives you the number of protons plus neutrons within the element or ion. From this information, we know that the number of neutrons would equal a minus z. So it's the mass number minus the atomic number. So that would be 27 minuteus 13, which would give us 14 neutrons. So so far, options b and c can be the only correct choices because in a, we do not have 27 neutrons. Now the charge is 3 plus. 3 plus means that you have lost electrons. It means you have lost 3 electrons. When aluminum is neutral, has no charge, it has an equal number of protons and electrons. Okay. But now we've lost 3 electrons, so what does that mean? That means we have 10 electrons remaining. So the answer would have to be C here, and if you want to double check that you can just say we have 13 protons and 10 electrons, so we know that would be plus 13 plus minus 10, which would give us plus 3 as an answer. That proves that our charge should be plus 3 here. So out of all the choices present, only option c gives the correct number for each of the subatomic particles.
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Problem
Problem
Give the correct number of protons, neutrons and electrons for the following isotope:.
A
35 protons, 35 neutrons, 81 electrons
B
35 protons, 46 neutrons, 36 electrons
C
81 protons, 46 neutrons, 82 electrons
D
35 protons, 46 neutrons, 34 electrons
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Problem
Problem
In which pair are the two species both isoelectronic and isotopic?
A
B
C
D
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Problem
Problem
One isotope of a metallic element has a mass number of 65 and 35 neutrons in the nucleus. The cation that this atom forms has 28 electrons. What is the symbol of the cation?
A
65Zn
B
65Ga3+
C
65Zn2+
D
65Ni2+
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Problem
Problem
Which of the following is the symbol for the ion with a +4 charge, 30 neutrons and 21 electrons?