Characteristics of Solids

Review One of over 118 types of pure substances from which all material are formed Element → The smallest particle of an element which all materials are formed. Atom →

The Periodic Table Is an organizational tool which can be used to predict chemical and physical characteristics of elements. It’s all in the family- For example, if you are in Family 18, the Noble Gases, you and all the other elements in that group/family – Neon, Argon, Krypton, Xenon and Radon have similar characteristics.

Group 18

The Staircase Metals : to the left of the “staircase” about 75% of all the elements lustrous, malleable, ductile, conduct heat and electricity  Nonmetals: on the right sides of the “staircase” dull, brittle, insulators Metalloids: on the staircase also know as semi-metals often semi- conductors some properties of both metals & nonmetals

How was the table formed? Chemists discovered that as the quantity of matter (atomic mass) increased, characteristics tended to repeat themselves in a predictable pattern. This was called “Periodicity.” When elements were placed in a table , those with similar properties were placed in a column, it produced vertical “Families.”

Rows and Columns Family = a vertical column (group) These elements have similar properties and reactivity Period = the 7 horizontal row Periods represents the number of layers of electrons in the atom.

An example of periodicity

example of periodicity

Column 18 Noble gases very stable don’t want to form compounds or bonds

Column 17 halogens want one more electron most reactive nonmetals can take an electron from almost anyone

Column 1 alkali metals want to give away one electron most reactive metals

Family Names

Trends Reactivity of metals In which direction does reactivity increase? To the left or to the right? Reactivity of Nonmetals Nonmetals react exactly the opposite of metals!!

MODEL OF A Lithium ATOM

3 types of Subatomic Particles Composition of an Atom 3 types of Subatomic Particles 1. Electrons → Is outside the nucleus and has a negative charge. 2. Protons → A positively charged particle in the nucleus of a Atom. It is ≈ the same mass as a Neutron 3. Neutron → An uncharged particle located in the Nucleus of an Atom. It is ≈ the same mass as a Proton.

Definitions Nucleus → Atomic Number → The central portion of an atom – usually consisting of protons and neutrons and contains almost all the mass of the atom. Atomic Number → A number representing the number of protons in an atom of an element.

Definitions Mass → The amount of material (stuff) in an object. Mass is proportional to weight. Mass does not change when gravity changes while weight does.

Subatomic Particles Number Atomic # Atomic mass – atomic # = Name Protons (p or +) Neutrons (n) Electrons (e-) Charge +1 No charge -1 Location in nucleus in shells around nucleus Mass ≈ 1 amu ≈ 2000 x smaller “Job” Determines identity of element Supplies proper mass to hold nucleus together Determines bonding/ how it reacts Number Atomic # Atomic mass – atomic # = # of neutrons Same as # of protons

Example Silver: Symbol Ag Atomic Number of Silver is? 47 How many Protons does Ag have? How many Electrons does Ag have? How many Electron layers? 5

Definitions Valence Electrons → Electrons found in the outermost energy level or layer from the nucleus. (These electrons are involved in bonding.) Metal have a tendency to lose their valence electrons. Nonmetals try to obtain valence electrons.

Finally we are done for today. Finish Periodic Table/ Atom Work Sheet

Crystal Structures Crystal → Crystal Lattice → An object with a regularly repeating arrangement of its atoms. Crystal Lattice → The pattern that atomic particles form in a crystalline solid.

14 different Crystalline Systems, most metals fall into 3 categories 1) Body-Centered Cubic (BCC) → A type of crystalline structure that is composed of 8 particles forming a cube with a 9th particle in the center of the cube.

14 different Crystalline Systems, most metals fall into 3 categories 2) Face-Centered Cubic (FCC) → A type of crystalline structure that is composed of 8 particles forming a cube and 6 more particles that are each centered in 1 of 6 faces of the cube.

14 different Crystalline Systems, most metals fall into 3 categories 3) Hexagonal-Close Packed (HCP) → A type of crystalline structure that is composed of 17 particles which are as closely packed as possible.

14 different Crystalline Systems, most metals fall into 3 categories Unit Cell → The simplest and smallest arrangement of atoms that can be repeated to form a particular crystal.

Formation of Solids Allotropes → Iron @ room Temp → BCC Elements which occur in more than one form due to the way their atoms are packed. Iron @ room Temp → BCC Iron above 910°C → FCC Carbon can be a diamond or graphite depending on how its atoms are packed.

Crystal Packing – loosely packed Is there another way these atoms could be arranged? Show next slide

Crystal Packing – More Densely Packed Most metals are close packed - that is, they fit as many atoms as possible into the available volume Alternating the atoms has made more room – the 4 halves could be joined and added to the bottom still leaving space.

Grains Influence Properties Rapid cooling produces smaller grains Slow cooling produces larger grains Alloys of metals with more grains make the material stronger

Crystal Grains “Crystal grains "are regions of regularity. At the grain boundaries atoms have become misaligned. The more grain boundaries there are (the smaller the individual crystal grains), the harder and more brittle the metal becomes. Heating a metal tends to shake the atoms into a more regular arrangement - decreasing the number of grain boundaries, and so making the metal softer. Banging the metal around when it is cold tends to produce lots of small grains. Cold working therefore makes a metal harder. To restore its workability, you would need to reheat it. You can also break up the regular arrangement of the atoms by inserting atoms of a slightly different size into the structure. Alloys such as brass (a mixture of copper and zinc) are harder than the original metals because the irregularity in the structure helps to stop rows of atoms from slipping over each other.

Crystal Slip Planes in Metal To reshape metals, layers of atoms are forced to slide over one another.

Crystal Structure Which type of crystal structure allows a metal to be more workable, one with many slip planes or one with fewer slip planes? Ones with many Slip Planes Which type of crystal structure allows a metal slip planes to be more workable, one that is closely packed or one that is loosely packed? Ones that are closely packed.

Type of Crystal Structure Closely Packed? Many Slip Planes? Workability FCC Yes Highest BCC No Medium HCP Lowest BCC FCC HCP Chromium Iron (<910˚C) Sodium Tungsten Aluminum Calcium Copper Gold Iron(>910˚C) Lead Nickel Platinum Silver Cobalt Magnesium Titanium Zinc

Model of Crystal Lab

Iron Wire Lab

Metallic & Non-Metallic Elements Metals tend to lose electrons which changes them from neutral atoms to positive ions. Nonmetal → Nonmetals gain electrons which changes them from neutral atoms to negative ions.

Metallic & Non-Metallic Elements Ion → An atom that has gained or lost at least one electron and has a negative or positive charge. Ionic Bond → A bond resulting from the attractive force between ions of opposite charges. (Metal & Non Metal bond to form a compound). A very strong bond.

Electron Transfer from a metal to a non metal Nonmetal atom becomes more stable by gaining electrons.

Sodium lets Chlorine use its valance electron

Type of Bonding Metallic Bond → The force that hold solid metal together. In Metallic bonds the outer electron are freely moving between each atom. This free movement gives metals many of their characteristic properties. ductile, conduct electricity, thermal conductor, etc…

Metallic Bonding All pure metals have metallic bonding and therefore exist as metallic structures.  Metallic bonding consists of a regular arrangement of positive ion cores of the metals surrounded by a mobile delocalized sea of electrons.

Covalent Bonding → A chemical attraction between 2 nonmetallic atoms that are sharing electrons. (Non-Metals).

Type of Bonding Molecules→ When 2 or more nonmetals share electrons to form covalent bonds. Van der Waal Forces → The weaker bonds that hold molecules to one another.

Bonding Van der Waal Forces Non-metal Atoms Covalent Bonds Molecular Compound Keeps the Molecules Together

Type of Bonding Covalent Network Solids → Group of solids that contain only covalent bonds and are made of extremely large molecules. Strong covalent bonds therefore very strong substances High melting points Examples are Diamond or Silicon Carbide

Covalent Crystals: This is a crystal which has covalent bonding between all of the atoms in the crystal. An example of this is a diamond.

metallic ionic covalent intermolecular Type of bonding metallic ionic covalent intermolecular Van der Waal forces Type of elements used Between metals Metals and nonmetals Between nonmetals Between molecules Givers &/or takers of electrons Between givers Between givers and takers Between takers Description Valence e- roam freely between many atoms (delocalized). Sea of e- surrounding (+) kernels. Transfer e- Makes (+) and (-) ions that are attracted to each other. Share e- Forms discrete molecules. Hold covalently bonded molecules together as a solid. Type of material formed Solid metallic elements and alloys Ceramics and glass Polymers and some ceramics/glasses Helps form solid polymers Strength of bond Relatively strong Very strong Weak Properties Produced Good conductors, workable, corrode easily, generally high melt temps but variable Brittle, high melt temps, nonconductors as solids, don’t corrode Insulators, Help determine a lot of properties of covalent compounds (polymers). Soft and plastic

Formation of Solids Lab