ENGR 54- Midterm Exam Guide - Comprehensive Notes for the exam ( 22 pages long!)
Document Summary
Compound substance composed of two or more elements. Alloy- materials that have metallic properties composed of more than one material. Different than compound because it is only metal. The higher the strength of the atom. The lower the coefficient of thermal expansion. Transfer of electrons from a low electronegativity to a high electronegative element. Difference in electronegativity should be at least 1. 7. All ionically bonded substances are compounds: covalent. *sio2 is between ionic and covalent: metallic. Cloud of electrons shared amongst many atoms. Only in elements (all atoms are the same) The difference in en should be zero because it is an element. *nondirectional- magnitude of the bond is equal in all directions around the ion. Crystal structures: bcc, fcc metallic bonds, hcp, diamond cube covalent bonds, zinc blend, rock salt ionic bonds, perovskite. *metals do(cid:374)"t si(cid:373)plify i(cid:374)to (cid:272)u(cid:271)es (cid:271)e(cid:272)ause they are (cid:374)ot (cid:272)lose pa(cid:272)ked. Rock salt (nacl) ionic structure, non directional bonds a=2(r1 + r2)
