Definition of an Ion
Let's recap a few things you probably learned a long time ago. There are 3 subatomic particles that are found in the atoms of an element. They are the positively charged protons, negatively charged electrons, and neutrons, which have no charge. Elements normally have the same number of protons and electrons in each of its atoms. This being the case, the atoms of the elements are neutral, meaning that they don't have a net positive or negative charge.
There are some instances when an atom may have a positive or negative charge. When the atom has a charge, it is now known as an ion. Atoms will pick up or lose electrons, which creates this charge. Electrons move around to reach the goal of having a full outermost shell within the atom in order to be stable.
Formation and Types of Ions
The positively charged protons always remain the same in an atom. The negatively charged electrons, however, can move from one atom to another. Ions form when an atom loses or gains electrons. Let's look at this a different way for a minute. You are making a decision, and you are weighing out your pros and cons. The pros are positive, and the cons are negative. You are at a point in your list where you have the same number of pros as cons. This would be the same as how the atom normally occurs.
Suddenly, you think of another con to add to the list. Now you have 1 more con than you do pros. This makes the decision more negative than it is positive. This same thing happens when an atom gains an electron. It now has more negatively charged particles than it does positively charged particles. A negatively charged atom has now become an ion known as an anion.
After thinking about things even more, you realize that you already have a solution for the con you just added, so you erase it. You are back to being even on your decision. Then you see that another con has also been resolved so you erase it as well. Now you have 1 more pro than you do cons. At this point, the decision is more positive than it is negative. This is the same as the neutral atom losing a negatively charged electron. It now has more positively charged particles than negatively charged ones. A positively charged atom that has now become an ion is known as a cation.
Examples of Ions
There are several commonly occurring ions. Let's look at some common anions first. Hydrogen usually has 1 proton and 1 electron. It sometimes gains an electron so that it has 2 electrons and still just 1 proton. It is now an anion named hydride.
There is also an example that you use every morning. You may be familiar with a substance called fluoride. This is found in your toothpaste. Fluoride is when fluorine has gained an electron. Fluorine has 9 protons and electrons until it gains an electron and becomes fluoride with 10 electrons and 9 protons.
Sometimes more than one electron is gained. Nitrogen has a tendency to gain up to 3 electrons to give it a total of 10 electrons, but it still has only the usual 7 protons. This means that the ion has a net charge of -3. The nitrogen ion is now called nitride.
Many positive ions commonly occur, too. Lithium, something that you see in batteries - which are incidentally called lithium ion batteries - usually has 3 protons and electrons. It loses 1 electron and then has a net charge of +1. Unlike with the anions, the name doesn't change when an atom goes from being neutral to being a cation.
Iron is an atom that can lose multiple electrons and has different ions. When iron loses 2 electrons, it has a net charge of +2 and is called iron (II). When iron loses 3 electrons, it has a net charge of +3 and is called iron (III).
Hydrogen is a special case because it gains or looses electrons equally. So in addition to the hydride anion, there is also a hydrogen cation. When hydrogen loses its only electron, then it has a +1 positive charge.
Atoms contain protons, subatomic particles with a positive charge; neutrons, subatomic particles with no charge; and electrons, subatomic particles with a negative charge. Ions are atoms that have lost or gained electrons and, therefore, have a net charge. An atom that has gained electrons and has a negative charge is an anion. An atom that has lost electrons and has a positive charge is a cation. Atoms gain or lose electrons in order to become more stable by having a full outermost shell of electrons. Examples of anions include hydride, fluoride, and nitride. Examples of cations include lithium, iron (II) and iron (III), and hydrogen. The net charge on the atom is the same as the number of electrons lost or gained.
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Ions are charged atoms, meaning a neutral atom has lost or gained electrons giving the atom an electric charge. Gaining electrons makes the atom negatively charged, and losing electrons makes the atom positively charged. Positive ions are called cations, and negative ions are called anions. For example, lithium loses 1 electron to become Li+1. The +1 indicates the ion has a +1 charge. Nitrogen gains 3 electrons and becomes N-3. The reason atoms gain or lose electrons is to either complete an outer energy level or to lose an outer energy level. Losing an outer energy level is easier for atoms that have only 1, 2 or 3 electrons in an energy level that typically needs 8 electrons to be full.
There are also polyatomic ions that contain multiple atoms that are covalently bonded together. An example of a polyatomic ion is NH4 +1.
Here are some more practice problems involving ions.
- Magnesium loses two electrons. What is its symbol?
- Oxygen gains two electrons. What is its symbol?
- Sodium loses one electron. What is its symbol?
- Carbonate is a polyatomic ion with a -2 charge. It has one carbon atom and three oxygen atoms. What is its formula?
- CO3 -2
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