Chapter 7 Ionic and Metallic Bonding

7.3

Valence Electrons

The valence electrons of atoms in a pure metal can be modeled as a sea of electrons. A metallic bond are forces of attraction between the free-floating valence electrons and the positively charged metal ions. • Properties of metals:

 Good conductors of electric current (because electrons can float freely in the metal)

 Ductile (can be drawn into wires)

 Malleable (can be hammered into shapes)

 Crystalline

Valence Electrons are electrons that are associated with an atom, it participates in forming a chemical bond. In addition they are electrons in the highest occupied energy level of an element's atoms. To find the number of valence electrons in an atom of a representative element, simply look at its group number.

7.1

Atoms form positive ions called cations and negative ions are called anions. Cations are produced when an atom loses one or more valence electrons. While an anion is produced when an atom gains one or more valence electrons. The name of an anion ends with -ide.

Electron Dot Structure

Formula Unit

An electron dot structure are diagrams that shows the number of valence electrons in the atoms of an element as dots. The electron dot structure can help predict the shape of a molecule based on simple rules such as number of bonds each element can make, lone pairs that each element can have, and how many total electrons each element can have total, ex. H can only have 2 shared electrons vs. carbon which can have 8 shared electrons

A formula unit is the lowest whole number ratio of ions in a ionic compound. Ex: Sodium chloride = 1:1 (one Na+ ion to each Cl- ion)

Magnesium chloride = (one Mg2+ ion to two Cl- ions)

Octet Rule

Atoms tend to achieve the electron configuration of a noble gas in order to become stable. An atom achieves the octet rule when there are 8 electrons in its outermost energy level. Atoms can achieve the octet rule by gaining or losing electrons. Ex: sodium chloride = sodium atom transfers its valence electron to the chlorine atom and both achieve the octet rule.

Quiz

1. An ionic compound is formed between:

a) a metal and a nonmetal

b) two metals

c) two nonmetals

2. How many valence electrons does oxygen have?

a) 2

b) 4

c) 6

d) 8

3. What is the charge on an oxide ion?

a) 1-

b) 2-

c) 3-

d) 4-

4. What is the chemical formula of the compound magnesium chloride?

a) MgCl3

b) Mg2Cl2

c) MgCl

d) MgCl2

5. How many electrons does a chlorine atom gain in order to achieve the octet rule?

a) 1

b) 2

c) 3

d) 4

7.2

An ionic compound is composed of anions and cations example: sodium chloride. An ionic compound exist as collections of positively and negatively charged ions arranged in repeating patterns. While an ionic bond are electrostatic forces that hold ions together in an ionic compound. • Properties of Ionic Compounds:

 Crystalline solids at room temperature.

 High melting points.

 Can conduct an electric current when melted or dissolved in water.

Chemical Formula

A chemical formula shows the number of atoms of each element in the smallest representative unit of a substance. Ex: Sodium chloride = NaCl, Magnesium chloride = MgCl2.

Chapter 7 Ionic and Metallic Bonding

By:Carlos and Mansi