Gaining and Losing Electrons

Next, let's review two atomic properties important to bonding that are related to the position of the element on the periodic table. They are the tendency or ability of atoms to lose electrons and the tendency or ability to gain electrons.

First, let's consider the ability to lose electrons. This is related to ionization energy, which you studied in a previous lesson. The ionization energy, of course, is the amount of energy that it takes to remove an electron from an atom. You have learned that the ionization energies are lowest for the elements down and on the left hand side of the periodic table and increase as you go up and all the way across to the right including the inert gases.

The ionization energy measures how hard it is to lose or remove an electron. High ionization energy means that it is hard to lose electrons. Low ionization energy means that it easy to lose electrons. The elements on the left side lose their electrons fairly easily and the elements on the right side of the periodic table do not lose their electrons very easily. Taking vertical position on the table into account, the elements that are lower on the table lose electrons more easily and the elements that are higher have a harder time losing electrons. Thus the overall trend is from most easily losing electrons on the lower left to least easily losing electrons on the upper right. Keep that trend in mind.

Ability to Lose Electrons

The ability to gain electrons is also related to the position on the periodic table. You should recall that as you go from left to right on the periodic table, the attraction for electrons increases and the ability to gain electrons increases. This is true all the way across the periodic table except for the inert gases. There is an abrupt drop in the ability to gain electrons when we get to the inert gases. This is because their energy level is full and any additional electrons will have to start a new energy level.

Ability to Gain Electrons

Practice

Take a moment now to clarify or firm up your thoughts about these atomic properties by doing the following (same as exercise 2 in your workbook). Check your work on the next page.

1. The phrases "hard to lose electrons" and "easy to gain electrons" are both similar and different. Comment on how they are similar as they pertain to elements on the periodic table. Comment on how they are different.

2. In each of the following sets, select the element that will most easily lose electrons.

Na, Cl

Mg, Fe

Na, K

Fe, Br

Si, Sn

3. In each of the following sets, select (circle) the element that will most readily gain electrons.

Na, Cl

Si, Sn

Cu, Br

N, F

Cl, Br

P, O

Answers

Hopefully you had little or no problem with these. If you did, please check with the instructor.

Generally, elements that find it hard to lose electrons do so for reasons that also make it easy to gain electrons (high effective nuclear charge and low number of energy levels). The exceptions to this generality are the inert gases which find it both hard to lose electrons (because of high effective nuclear charge) and hard to gain electrons (because of a full outer energy level). --Note: there are a variety of correct ways to respond to this question.

2. In each of the following sets, select the element that will most easily lose electrons.

3. In each of the following sets, select (circle) the element that will most readily gain electrons.

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