Which Elements Would You Expect To Gain Electrons In Chemical Changes

(A newer version of the Chemic Reactions module is available.)

The reaction of two or more elements together results in the germination of a chemical bond between atoms and the formation of a chemical compound (see our Chemical Bonding module). But why do chemicals react together? The reason has to do with the participating atoms' electron configurations (see our The Periodic Table of Elements module).

Inert gases

In the late 1890s, the Scottish pharmacist Sir William Ramsay discovered the elements helium, neon, argon, krypton, and xenon. These elements, along with radon, were placed in group VIIIA of the periodic table and nicknamed inert (or noble) gases because of their trend not to react with other elements (see our Periodic Tabular array page).

The trend of the noble gases to not react with other elements has to do with their electron configurations. All of the noble gases accept total valence shells; this configuration is a stable configuration and one that other elements try to achieve by reacting together. In other words, the reason atoms react with each other is to achieve a state in which their valence shell is filled.

Metals

Let's look at the reaction of sodium with chlorine. In their atomic states, sodium has one valence electron and chlorine has vii.

Chlorine, with seven valence electrons, needs one boosted electron to consummate its valence shell with eight electrons. Sodium is a trivial chip trickier. At start it appears that sodium needs seven additional electrons to complete its valence shell. But this would give sodium a -seven electrical charge and brand it highly imbalanced in terms of the number of electrons (negative charges) relative to the number of protons (positive charges). As it turns out, it is much easier for sodium to surrender its 1 valence electron and go a +i ion. In doing so, the sodium atom empties its third electron shell and at present the outermost shell that contains electrons, its second beat out, is filled - agreeing with our earlier statement that atoms react because they are trying to fill their valence shell.

This trait, the tendency to lose electrons when entering into chemic reactions, is common to all metals. The number of electrons metallic atoms will lose (and the charge they will accept on) is equal to the number of electrons in the atom's valence beat. For all of the elements in grouping A of the periodic table, the number of valence electrons is equal to the group number (encounter our Periodic Table folio).

Comprehension Checkpoint

Metals tend to __________ electrons in chemical reactions.

Nonmetals and metalloids

Nonmetals, past comparison, tend to gain electrons (or share them) to complete their valence shells. For all of the nonmetals, except hydrogen and helium, their valence shell is complete with viii electrons. Therefore, nonmetals proceeds electrons corresponding to the formula = viii - (group #). Chlorine, in group 7, will gain 8 - 7 = 1 electron and form a -ane ion.

Hydrogen and helium only have electrons in their first electron shell. The capacity of this shell is two. Thus helium, with two electrons, already has a total valence trounce and falls into the grouping of elements that tend non to react with others, the noble gases. Hydrogen, with ane valence electron, volition gain 1 electron when forming a negative ion. However, hydrogen and the elements on the periodic table labeled metalloids, tin can actually class either positive or negative ions corresponding to the number of valence electrons they have. Thus hydrogen will form a +1 ion when it loses its one electron and a -one ion when it gains one electron.

Comprehension Checkpoint

Metalloids are elements that can form either positive or negative ions.

Reaction energy

All chemical reactions are accompanied by a change in free energy. Some reactions release energy to their surroundings (usually in the form of heat) and are chosen exothermic. For example, sodium and chlorine react so violently that flames can exist seen as the exothermic reaction gives off heat. On the other manus, some reactions demand to absorb estrus from their surround to proceed. These reactions are chosen endothermic. A adept instance of an endothermic reaction is that which takes identify inside of an instant "cold pack." Commercial cold packs unremarkably consist of two compounds – urea and ammonium chloride – in separate containers inside a plastic bag. When the purse is bent and the inside containers are broken, the two compounds mix together and begin to react. Because the reaction is endothermic, it absorbs rut from the surrounding surround and the bag gets cold.

Reactions that proceed immediately when two substances are mixed together (such as the reaction of sodium with chlorine or urea with ammonium chloride) are called spontaneous reactions. Not all reactions keep spontaneously. For case, think of a match. When y'all strike a match you are causing a reaction between the chemicals in the friction match head and oxygen in the air. The match won't light spontaneously, though. You start need to input free energy, which is called the activation energy of the reaction. In the instance of the match, you supply activation energy in the form of rut past striking the match on the matchbook. After the activation energy is absorbed and the reaction begins, the reaction continues until you either extinguish the flame or y'all run out of material to react.

Summary

Exploring the how and why of chemical reactions, this module describes backdrop of the inert – or "noble" – gases. It also explains how different elements attain a stable configuration by bonding to make full their valence shells with electrons, resulting in a chemical chemical compound. The deviation between exothermic and endothermic reactions is discussed.