Is sodium chloride electrovalent

The ionic bond

A closer look at the formation of NaCl

Basically, the most important thing about the formation of NaCl has already been said: The Na atoms have one electron too many, the Cl atoms have one electron too little. So that both types of atoms come into the coveted noble gas state, each Na atom simply gives up its excess electron, and each Cl atom accepts one of these given electrons. Both are then "happy" noble gas atoms, but with sodium or chlorine atomic nuclei and a positive or negative charge. This important process is illustrated in the next picture:

At the top left we see a sodium atom with one outer electron (highlighted in green), at the bottom left a chlorine atom with seven outer electrons is shown. These two atoms represent the starting materials for the reaction between sodium and chlorine to form sodium chloride.

After the electron transfer, the particles look like the one shown on the right. The sodium atom has become a positively charged sodium ion (colored red), and the chlorine atom has become a negatively charged chloride ion through the absorption of the electron (colored blue).

What does the thick green double arrow between the sodium and the chloride ion on the right-hand side mean?

N / A+- and Cl--Ions attract each other. An incredible number of sodium and chlorine atoms or ions take part in the reaction, not just two or four. All of these many positive and negative ions attract each other. This creates a regularly structured crystal. Each sodium ion is surrounded by six chloride ions, and each chloride ion is surrounded by six sodium ions.

On this picture from the Engl. Wikipedia shows the regular structure of the NaCl crystal very nicely. Of course, this picture only shows a tiny section of the actual crystal. On the dawgsdk.org website, you can even admire a real three-dimensional representation of the NaCl crystal, which you can rotate in all directions with the mouse. However, this page requires Flash.

Crystals have a very regular structure and look that way when you look at them with the eye. Sodium chloride crystals are easy to make at home. To do this, you have to dissolve a lot of NaCl in water until a saturated solution is formed. This is then left in a cool and, above all, vibration-free place for several days. The latter is usually the main problem, because where is it really vibration-free? Every passing car, every walk through the room leads to vibrations that have a negative effect on crystal growth.

Salt formation

We want to generalize now. What happened between sodium and chlorine also takes place in many other reactions between metals and non-metals. The oxidation of iron or copper was already discussed in the 7th grade.

Iron atoms have two outer electrons, oxygen atoms six outer electrons. It is now clear what happens in the reaction between iron and oxygen: The iron atoms give off their two outer electrons, and bivalent positive iron ions are formed. The oxygen atoms, on the other hand, take on two electrons, and bivalent negative oxygen ions are created, which are not called oxygen ions, but oxide ions.

The positive iron ions and the negative oxide ions attract each other and a solid iron oxide crystal is formed.

When salts are formed, the atoms of a metal give off the external electrons, which creates positively charged metal ions. The atoms of the non-metal, on the other hand, absorb missing electrons, negatively charged non-metal ions are formed. The driving force for both processes is the "urge" of the atoms to attain a noble gas state. The oppositely charged ions attract each other and form a solid crystal lattice. Here each metal ion is surrounded by a fixed number of non-metal ions, and conversely, each non-metal ion is surrounded by a certain number of metal ions.

There are different crystal structures in nature, but we do not want to go into any further here. There is a special page for this on this homepage.

The ionic bond

"Theionic bond (alsoIonic bondheteropolar bond orelectrovalent bond) is a chemical bond based on the electrostatic attraction of positively and negatively charged ions. "

This Wikipedia quote from the article "Ionic bond" sums up briefly and summarizes what is meant by the technical term ionic bond. The formation of sodium chloride from the elements sodium and chlorine is the prime example of the formation of ionic bonds. In the narrower sense of the term, "ionic bond" means the electrical attraction that exists between two oppositely charged ions, for example between a positive sodium ion and a negative chloride ion.

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Experiment - First interpretation - Ionic bond - Energy aspects - Melting points - Crystal structures