Bonding and Structure in Solids SCH4U

Structure in solids Crystalline Solids: the atoms, ions, or molecules are ordered in well-defined three-dimensional arrangements. Have faces and make definite angles. Amorphous solids: a solid in which particles have no orderly structure. There is no well-defined shape or face. Solids do not stack well together. Eg. Rubber or Glass

Crystalline vs. Amorphous Structures

Types of Solids Solids are held tightly by significant intermolecular forces. We can classify solids based on the type of intermolecular force holding the together 1.Molecular Solids 2. Covalent Solids 3. Ionic Solids 4. Metallic Solids

**Structures of Crystalline Solids (AP) ** Each repeating unit is reffered to as a Unit Cell. Unit cells create a crystal lattice. Unit Cell  Crystal Lattice 

Types of Unit Cells There are seven basic types of unit cells. Cubic Unit Cell Primitive Cubic Body Centered Cubic Face-Centered Cubic Each has a different arrangement of lattice points.

Types of Unit Cells

Sample Problem Determine the net number of Na+ and Cl- ions in the NaCl unit cell shown in the Figure.

Sample Problem Determine the net number of Na+ and Cl- ions in the NaCl unit cell shown in the Figure.

Close Packing of Spheres Arrangement of particles in closest contact to maximize attractive forces. Hexagonal Close Packing ABAB pattern Cubic Close Packing  ABCA Pattern

** AP** Structure and Bonding in Metals* Extra Resources https://chem.libretexts.org/Core/Physical_and_Theoret ical_Chemistry/Physical_Properties_of_Matter/States_of _Matter/Properties_of_Solids/Crystal_Lattice/Closest_P ack_Structures http://faculty.sites.uci.edu/chem1l/files/2013/11/RDGc rystallinesolids.pdf http://apchemistrynmsi.wikispaces.com/file/view /10+IMFs%2CSolids+%26+Liquids.pdf Read pages 8-9

1. Molecular Solids Substances who’s particles are molecules. Molecules are not strongly attracted together. Intermolecular Forces include: London Dispersion Forces. Some may include dipole-dipole forces and hydrogen bonding Characterized by: Low Melting and Boiling Points Non-conductors

H-bonds become rigid, forming a lattice like structure 1. Molecular Solids Examples include Iodine, I2 (solid at room temperature) Neon, Ne(m.p.=-248°C) Solid CO2 ( mp -78.15°C ) Ice (H2O) Sugar H-bonds become rigid, forming a lattice like structure

2. Metallic Solids Metals have very strong intermolecular forces binding their atoms together  not fully understood. Metals, are substances that typically have a very high melting point. Most have b.p of above 1000°C Except Mercury  melts at -39°C Gallium  melts at 30°C https://www.youtube.com/watch?v=aolRO9eteSk

2. Metallic Solids Valence electrons are typically in s or d sub-shell. Electrons of neighboring atoms combine to form ‘electron soup’ that acts as a ‘glue’ to hold the positive nuclei of metal atoms together. These are called delocalized electrons. The outer electrons are so weakly bound to metal atoms that they are free to roam across the entire metal. Having ‘lost’ their outer electrons, individual metal atoms are more like positive ions in a swarm of communal electrons.

3. Metallic Solids Electron Sea Theory is a theory that states that the electrons in a metallic crystal move freely around the positively charged nuclei

Rice Krispy Analogy! Rice Krispy squares are an excellent analogy for metal solids. The marshmellow represents the delocalized electrons, and the rice are the positive metal ions.

Other Properties

3. Ionic Solids Substances who’s particles are ions --. Have completely given away or gained an electron. An ionic compound is considered to be held by intramolecular forces. Forms ions  opposite ions attract  ionic Bond

3. Ionic Solids Some properties of metals include: They have very high melting points They are brittle; they do not bend and putting too much stress causes them to break Soluble in Water In a solid state, do not conduct electricity In a liquid, or molten state, they are electrically conductive.

3. Ionic Solids

4. Covalent Network Solids Consists of atoms held together by large networks or changes by covalent bonds. Every atom is bonded forming a 3-D network C & Si  tend to form covalent network solids. Eg: Diamond, Graphite, Silica and Asbestos. Very high melting points Extremely hard substances Poor conductors of electricity

Diamond Allotrope of carbon Every carbon is bonded with 4 other carbons Extremely high crystal lattice energy resulting in characteristic hardness and high melting point.

Graphite Allotrope of carbon Each carbon forms a trigonal planar geometry Crystal structure forms ‘sheets’ of covalently bonded carbons. Sheets are not bonded together and as a result, slide over one another easily ( pencils! ) Unique fact: Carbon is a nonmetal, but graphite conducts electricity!

Diamond vs Graphite

Quartz Crystal

Bonding in Crystalline Solids

Reminder: Test on Monday, October 30, 2017 Homework SCH4U In-Class Worksheet Types of Solids Assignment Design lab procedure for next class Read 4.3 (p.196-207) q’s p. 208 # 1-10 Chapter 4 Review  pg. 209 # 1-31 SCH4U- AP Read 11.7 & 11. 8 Q’s pg. # 471 69-78 Reminder: Test on Monday, October 30, 2017

Test Topics SCH4U : Chapter : 4.1, 4.2, 4.3 Ionic, Covalent and Metallic Bonding Lewis Structures VSEPR Shapes Polarity & Properties Intermolecular Forces Types of Solids SCH4U : Chapter : 4.1, 4.2, 4.3 SCH4U- AP - 8.1-8.7, 9.1 -9.3, 11.1-11.2, 11.7-11.8