Ionic and Metallic Bonding Chapter 6

Ions Elements within each group of the periodic table behave similarly because they have the same number of valence electrons. Valence electrons are the electrons in the highest occupied energy level of an elements atoms. Valence electrons determine the chemical properties of an element.

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

Octet Rule In forming compounds, atoms tend to gain or lose electrons in order to achieve the electron configuration of a noble gas!!!

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Key Concept Atoms of metals lose their valence electrons. Atoms of some nonmetals ten to gain electrons or to share with other nonmetallic elements to achieve a complete octet

Formation of Cations When an atom loses an electron it produces a positively charged ion, or a cation. The most common cations are those produced by the loss of valence electrons from metal atoms.

Electron–Dot Structures for Ions Remove electrons for cations Sodium Atomic number 11 1s22s22p63s1 Na 1 Valence electron Remove electron to form ion + Na Sodium Ion Atomic number 11 1s22s22p63s0 Now has full shell with similar electronic configuration to Neon --Stable noble gas configuration

Formation of Anions The gain of negatively charged electrons by a neutral atom produces an anion.

Electron–Dot Structures for Ions Add electrons for anions Chlorine atomic number 17 1s22s22p63s23p5 7 Valence electrons Cl Add electron to form ion - Chloride ion atomic number 17 1s22s22p63s23p6 Cl 8 Valence electrons Now has full shell with similar electronic configuration to Argon --Stable noble gas configuration

Mg Lewis Dot Structures Mg example 1s22s22p6 3s2 [Ne] 3s2 The valence shell is the outermost shell of electrons of an atom. Mg example 1s22s22p6 3s2 [Ne] 3s2 2 electrons in the valence Shell Use dots to represent Valence Electrons Mg

Electron-Dot Structures Valence electrons represented by dots Electron-dot symbols – Examples: Na•, •Mg•, …

Ionic Bonds Compounds composed of cations and anions are called ionic compounds. Although they are composed of ions, ionic compounds are electrically neutral. The electrostatic forces that hold ions Together in ionic compounds are Called Ionic bonds.

Ionic Bonds: One Big Greedy Thief Dog!

Formula Units A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. Because an ionic compound exists as a collection of positively and negatively charged ions arranged in repeating patterns, its chemical formula refers to a ratio known as a formula unit.

For NaCl the ratio of the ions is 1:1 (one Na+ to one Cl-) A formula unit is the lowest whole-number ratio of ions in an ionic compound. For NaCl the ratio of the ions is 1:1 (one Na+ to one Cl-) What is the formula unit for Magnesium Chloride?

Practice, Practice, Practice Use electron dot structures to determine formulas of the ionic compounds formed when 1. potassium reacts with iodine. 2. Aluminum reacts with oxygen.

Properties of Ionic Compounds Most are crystalline solids at room temperature. High melting points. Conduct electricity when melted or dissolved in water.

Practice, Practice Write the formulas for each compound. Barium chloride Lithium oxide Magnesium oxide Calcium flouride

7.3 Bonding in Metals The valence electrons of metal atoms can be modeled as a sea of electrons. That is, the valence electrons are mobile and can drift freely from one part of the metal to another. Metallic Bonding Animation

Metallic Bonds: Mellow dogs with plenty of bones to go around.

Alloys Mixtures composed of two or more elements, at least one of which is a metal. Their properties are often superior to those of their component elements.

Learning Check Give the ionic charge for each of the following: A. 12 p+ and 10 e- 1) 0 2) 2+ 3) 2- B. 50p+ and 46 e- 1) 2+ 2) 4+ 3) 4- C. 15 p+ and 18e- 2) 3+ 2) 3- 3) 5-

Learning Check A. Number of valence electrons in aluminum 1) 1 e- 2) 2 e- 3) 3 e- B. Change in electrons for octet 1) lose 3e- 2) gain 3 e- 3) gain 5 e- C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+

Solution A. Number of valence electrons in aluminum 3) 3 e- B. Change in electrons for octet 1) lose 3e- C. Ionic charge of aluminum 3) 3+

Review.. What is a chemical bond? Force that holds two atoms together What is an ionic bond? An electrostatic force that holds oppositely charged particles together in an ionic compound Forms when….? What are atoms and compounds always trying to achieve? Stability Complete set of valence electrons…