Unit 2 Molecular and Ionic Compound Structure and Properties, Slides of Molecular Structure

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Unit 2

Molecular and Ionic

Compound Structure and

Properties

Agenda 9/26/

● Types of Solids ○ Summarizing ● Metallic structure models ○ Alloys ○ Heat-Treating Steel labette

Ionic Solids - metal and nonmetal atoms form a

lattice of alternating positive and negative ions held

together by ionic bonds.

Examples: Iron(II) Sulfide (FeS) Calcium Bromide (CaBr 2 ) Sodium Chloride (NaCl) Formula units Not conductive as a solid Ionic bonds have to be broken to melt the solid - ions will be present in the liquid high mpts and enthalpies of fusion NaCl(s) → NaCl(l) ΔH (^) fus kJ/mol Often soluble in water; solutions of ionic compounds conduct electricity

What property of ionic solids does the particulate

level diagram help us understand?

Molecular Solids - nonmetal atoms form molecules

with covalent bonds which are held together in a

solid by intermolecular forces of attraction

Examples: Nitrogen (N 2 ), Ice (H 2 O), Dry ice (CO 2 ) Molecular structure Not conductive as a solid Intermolecular forces broken to melt the solid - molecules will be present in the liquid Low mpts and enthalpies of fusion (lowest of the 4 types of solid) H 2 O(s) → H 2 O(l) ΔH (^) fus kJ/mol Slightly soluble in water; not conductive as aqueous solution

Network Covalent Solids - nonmetal atoms form a

lattice structure held together with covalent bonds.

Examples: diamond (Carbon), Silica (SiO 2 ), Silicon (Si) Formula units (no distinct molecules) Not conductive as a solid Covalent bonds have to be broken to melt the solid - atoms will be present in the liquid Highest mpts and enthalpies of fusion of all the types of solids C (^) diamond (s) → C(l) ΔH (^) fus kJ/mol Insoluble;

What property of metals can be explained using the

particulate level diagram below?

What property of metals can be explained using the

particulate level diagram below?

Malleability - shows how because it shows how adjacent

layers of positive ions can move relative to one another while

remaining in full contact with the electron sea.

Heat-treating steel - read all the instructions.

Don’t heat beyond red hot - too much heat and you start

burning out the carbon in the steel.

Bobby pins are high carbon steel (0.7%)

Paper clips are low carbon steel (0.2%)