1. Ions
7.1
Pyrite (FeS2), a common mineral that emits sparks when struck against steel, is often mistaken for gold—hence its nickname, “fool’s gold.” Pyrite is an example of a crystalline solid. In this chapter, you will learn about crystalline solids composed of ions that are bonded together. But first you need to understand how ions form from neutral atoms.

2. 7.1
Valence Electrons
Valence Electrons
How do you find the number of valence electrons in an atom of a representative element?

3. 7.1
Valence Electrons
To find the number of valence electrons in an atom of a representative element, simply look at its group number.

4. 7.1
Valence Electrons
Valence electrons are the electrons in the highest occupied energy level of an element’s atoms.
The number of valence electrons largely determines the chemical properties of an element.

5. 7.1
Valence Electrons
Electron dot structures are diagrams that show valence electrons as dots.

6. 7.1
The Octet Rule
The Octet Rule
Atoms of which elements tend to gain electrons? Atoms of which elements tend to lose electrons?

7. 7.1
The Octet Rule
Atoms of metals tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some non-metals tend to gain electrons or to share electrons with another nonmetal to achieve a complete octet.

8. 7.1
The Octet Rule
Noble gases, such as neon and argon, are unreactive in chemical reactions. In 1916, chemist Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules.
He called his explanation the octet rule: In forming compounds, atoms tend to achieve the electron configuration of a noble gas.

9. 7.1
Formation of Cations
Formation of Cations
How are cations formed?

10. 7.1
Formation of Cations
An atom’s loss of valence electrons produces a cation, or a positively charged ion.

11. 7.1
Formation of Anions
Formation of Anions
How are anions formed?

12. 7.1
Formation of Anions
The gain of negatively charged electrons by a neutral atom produces an anion.
An anion is an atom or a group of atoms with a negative charge.
The name of an anion typically ends in -ide.

13. All halogen atoms have seven valence electrons.
7.1
Formation of Anions
The ions that are produced when atoms of chlorine and other halogens gain electrons are called halide ions.
All halogen atoms have seven valence electrons.
All halogen atoms need to gain only one electron to achieve the electron configuration of a noble gas.

14. 7.1
Conceptual Problem 7.1

15. 7.1
Conceptual Problem 7.1

16. 7.1
Conceptual Problem 7.1

17. 7.1 Section Quiz.
7.1.

18. 7.1 Section Quiz.
1. How many valence electrons are there in an atom of oxygen? 2 4 6 8

19. 7.1 Section Quiz.
2. Atoms that tend to gain a noble gas configuration by losing valence electrons are
metals.
nonmetals.
noble gases.
representative elements.

20. 7.1 Section Quiz.
3. When a magnesium atom forms a cation, it does so by
losing two electrons.
gaining two electrons.
losing one electron.
gaining one electron.

21. 7.1 Section Quiz.
4. When a bromine atom forms an anion, it does so by
losing two electrons.
gaining two electrons.
losing one electron.
gaining one electron