Unit 5 Test

1. Unit 5 Test What You Need to Know !! • Periodic Table History • Medeleev (original) • ordered by atomic mass & • Columns by similar chemical properties • “periodic law” • Mosely (present) • Ordered by atomic number • Periodic Table Structure • Periods • Horizontal row • Valence e-s in same principal energy levels (PEL’s) • Period number = number of outermost PEL • Group • Vertical columns • Same number of valence electrons • Similar chemical properties • Groups 1-12 are metals (alkai,alkaline, transition) • Groups 13-16 mix of metals, metalloids, nonmetals • Groups 17- halogens • Groups 18 – noble gases

2. Group 1 & Group 2 – ALKALI & ALKALINE EARTH METALS • Highly reactive • most reactive of metals • more reactive as move down the group • group 1 more slightly more reactive than group 2 • Groups 3-12 – TRANSITION METALS • Less reactive • Some like gold (Au), platinum (Pt) and silver (Ag) are relatively unreactive • Others like nickel (Ni), tin (Sn), iron (Fe), and aluminum (Al) are fairly reactive • Form color ions in solution • Hard except for mercury ,Hg, (liq) • High melting and boiling points • METALLOIDS (SEMIMETALS) • Exhibit properties of both metals & nonmetals • along diagonal “staircase” in groups 13 -16 • SI and Ge most widely known • GROUP 17 – HALOGENS • Highly reactive • most reactive of nonmetals • more reactive as move up the group • Only group to exhibit all 3 phases of matter • Exist as diatomic molecules • each has distinctive color and odor • GROUP 18 – NOBLE (RARE) GASES • Highly nonreactive (inert) • exist as monatomic gases • Neon, Argon, Krypton • used in lighting

3. FACTORS in PERIODIC TABLE TREND: A) Nuclear Charge: Number of protons in the nucleus. The larger the # of protons (atomic number) the greater the charge; the greater the charge the stronger the attraction for electrons. B) Electron Shielding: the layers of electrons between the nucleus and the outermost electron. These inner electrons shield the outermost electron from the full attractive force of the nucleus. The larger the number of the principal energy levels (PEL), the more layers of shielding. The more layers of shielding, the less the pull on the electron. C) Principal Energy Level: The higher the PEL level, the higher the electron energy. The higher the PEL level, harder for nucleus to attract outermost electrons decreasing metallic characteristics L to R in Period GAS SOLID increasing # of valence electrons Top to Bottom in Group increasing number of PEL’s increasing metallic properties SOLID

4. “in summary …” Generalized Metal vs Nonmetal Comparisons allotrope – one of two or more different forms of an element in the same phase >(different physical & chemical properties) Ex Oxygen (O2, O3), Carbon (graphite, diamonds)