Practice problems

1. Without looking at the Periodic Table, give the group, period, and block in which the element that has the following electron configuration, is located: [Xe]6s².

2. Without looking at the Periodic Table, write the electron configuration for the element in the third period in Group 1. Is this likely to be more or less active than that described in question #1?

3. Without looking at the Periodic Table, give the group, period, and block in which the element with the following shorthand electron configuration is located: [Kr]5s¹.

4. How does the reactivity of the element in question # 1 compare with that in Group 1 of the same group?

Chapter # 4. Chemical bonding

Vocabulary

English	Українська назва	English	Українська назва
Electrostatic attraction	Електростатичне притягування	Ionic bond	Іонний зв’язок
Unpaired electron	Неспарений електрон	Covalent bond	Ковалентний зв’язок

Sourses:

1. Introduction in General, Organic and Biochemistry, 7^th Edition, by Morris Hein, Leo R. Best, Scott Pattison and Susan Arena, Brooks/Cole Publishing Co., 2001. (Chapter 6, pp. 161-190);

2. http://hyperphisics.phy-astr.gsu.edu/hbase/chemical/bond.html

I solated and electrically neutral atoms are rare in nature. Ordinarily, only noble-gas atoms exist independently. Atoms of other elements are usually combined with each other or with atoms of different elements. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms (Fig. 6).

Energy

B

E (B)

AB

E (AB)

A

E (A)

∑ (E(A) + E(B)) > E (AB)

A, B - separated atoms;

AB - compound

Figure 6. Condition for chemical bond formation

Atoms are held together by electrostatic attraction between positively charged nuclei and negatively charged electrons. This attraction permits two atoms to be held together by a chemical bond, which is a link between atoms that results from the mutual attraction of their nuclei for electrons. Chemical bonds are classified by the way in which valency electrons are distributed around the nuclei of the combined atoms.

1. Types of Chemical Bonds

In previous chapter we described how atoms of main group elements could gain or lose electrons to form ions with noble-gas electron configurations. Metals tend to lose electrons to form positive ions, and non-metals tend to gain electrons to form negative ions. Many chemical compounds are composed of ions; in these compounds the chemical bond is an ionic one. An ionic bond is the chemical bond resulting from electrostatic attraction between positive and negative ions. If these is a purely ionic bond, one atom has completely given up one or more electrons, and another atom has gained them - as illustrated for two atoms that each have one unpaired electron at the top in Figure 7.

A⁺ : B^-