why does a sodium ion have a positive charge

We've talked about ions before. Now it's time to get down to basics. The
atomic number of an, also called a proton number, tells you the number of protons or positive particles in an. A normal atom has a neutral charge with equal numbers of positive and negative particles. That means an atom with a neutral charge is one where the number of is equal to the atomic number. Ions are atoms with extra electrons or missing electrons. When you are missing an electron or two, you have a positive charge. When you have an extra electron or two, you have a negative charge. What do you do if you are a (Na) atom? You have eleven electrons one too many to have an entire filled. You need to find another element that will take that electron away from you. When you lose that electron, you will youвll have full shells. Whenever an atom has full shells, we say it is happy. Let's look at (Cl). Chlorine has seventeen electrons and only needs one more to fill its third shell and be happy. Chlorine will take your extra sodium electron and leave you with 10 electrons inside of two filled shells. You are now a happy atom too. You are also an ion and missing one electron. That missing electron gives you a positive charge. You are still the element sodium, but you are now a sodium ion (Na ). You have one less electron than your atomic number. So now you've become a sodium ion. You have ten electrons. That's the same number of electrons as (Ne). But you aren't neon. Since you're missing an electron, you aren't really a complete sodium atom either. As an ion you are now something completely new. Your whole goal as an atom was to become a happy atom with completely filled electron shells. Now you have those filled shells. You have a lower energy. You lost an electron and you are happy.


So what makes you interesting to other atoms? Now that you have given up the electron, you are quite electrically attractive. Other electrically charged atoms (ions) of the opposite charge (negative) are now looking at you and seeing a good partner to bond with. That's where the chlorine comes in. It's not only chlorine. Almost any ion with a negative charge will be interested in bonding with you. Don't get worried about the big word. Electrovalence is just another word for something that has given up or taken electrons and become an ion. If you look at the, you might notice that elements on the left side usually become positively charged ions (cations) and elements on the right side get a negative charge (anions). That trend means that the left side has a positive valence and the right side has a negative valence. Valence is a measure of how much an atom wants to with other atoms. It is also a measure of how many electrons are excited about bonding with other atoms. There are two main types of bonding, covalent and electrovalent. You may have heard of the term ionic bonds. Ionic bonds are electrovalent bonds. They are just groups of charged ions held together by electric forces. Scientists call these groups ionic agglomerates. When in the presence of other ions, the electrovalent bonds are weaker because of outside electrical forces and attractions. Sodium and chlorine ions alone have a very strong bond, but as soon as you put those ions in a solution with H, OH, F ions, there are charged distractions that break the Na-Cl bond. Look at sodium chloride (NaCl) one more time. Salt is a very strong bond when it is sitting on your table. It would be nearly impossible to break those ionic/electrovalent bonds.


However, if you put that salt into some water (H O), the bonds break very quickly. It happens easily because of the electrical attraction of the water. Now you have sodium (Na ) ions floating around the solution. You should remember that ionic bonds are normally strong, but they are very weak in water. Atoms (or groups of atoms) in which there are unequal numbers of protons and electrons are called ions. Usually, the number of protons and electrons in atoms are equal. But there are cases in which an atom can acquire an electrical charge. For example, in the compound sodium chloride table salt the sodium atom has a positive charge and the chlorine atom has a negative charge. The neutral sodium atom has 11 protons and 11 electrons, which means it has 11 positive charges and 11 negative charges. Overall, the sodium atom is neutral, and it s represented like this: Na. But the sodium ion contains one more positive charge than negative charge, so it s represented like this: This unequal number of negative and positive charges can occur in one of two ways: An atom can gain a proton (a positive charge) or lose an electron (a negative charge). So which process is more likely to occur? In general, it s easy to gain or lose electrons but very difficult to gain or lose protons. So atoms become ions by gaining or losing electrons. And ions that have a positive charge are called cations. The progression goes like this: The sodium ion shown above is formed from the loss of one electron. Because it lost an electron, it has more protons than electrons, or more positive charges than negative charges, which means it s now called the: Likewise, when the neutral magnesium atom loses two electrons, it forms the: Now consider the chlorine atom in sodium chloride.


The neutral chlorine atom has acquired a negative charge by gaining an electron. Because it has unequal numbers of protons and electrons, it s now an ion. And because ions that have a negative charge are called anions, it s now called the: You can write electron configurations and energy level diagrams for ions. The neutral sodium atom (11 protons) has an electron configuration of: The sodium cation has lost an electron the valence electron, which is farthest away from the nucleus (the 3s electron, in this case). The electron configuration of the sodium ion is: This is the same electron configuration as the neutral Argon atom. If two chemical species have the same electron configuration, they re said to be isoelectronic. The preceding examples are all monoatomic (one atom) ions. But polyatomic (many atom) ions do exist. The ammonium ion is a polyatomic ion, or, specifically, a polyatomic cation. It is written as: The nitrate ion, is also a polyatomic ion, or, specifically, a polyatomic anion. It is written as Ions are commonly found in a class of compounds called salts, or ionic solids. Salts, when melted or dissolved in water, yield solutions that conduct electricity. A substance that conducts electricity when melted or dissolved in water is called an electrolyte. Table salt sodium chloride is a good example. On the other hand, when table sugar (sucrose) is dissolved in water, it becomes a solution that doesn t conduct electricity. So sucrose is a nonelectrolyte. Whether a substance is an electrolyte or a nonelectrolyte gives clues to the type of bonding in the compound. If the substance is an electrolyte, the compound is probably ionically bonded. If it s a nonelectrolyte, it s probably covalently bonded.

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