Chpt 17 Quiz! 1.The currently-accepted model of the atom is called the _________________? 2.___________ and ___________ are needed to determine the atomic mass. 3.How many protons does Bromine have? 4.Which element has two energy levels and five valence electrons? 5.Atoms of the same element that have different number of neutrons are called _____________. 6.Atoms are placed on the periodic table in order of increasing ______________. 7.Quarks are particles of matter that make up ____________ and _____________.

Trends in the Periodic Table

Metals 1. ¾ of the elements are metals Not all metals are hard Ex: Manganese- the metal that isn’t It behaves like the transition elements only when its alloyed with other metals, then it adds strength and flexibility 2.Shiny (silvery metallic luster) 3.Most are solids at room temperature 4.Good conductors of heat and electricity 5.Malleable- can be flattened into sheets 6.Ductile- can be stretched into wire 7.Can give up valence electrons easily

Group 1 Alkali Metals Have similar properties because each has only one valence electron Soft metals Extremely reactive- single electron can be removed easily Ex: if you drop a small piece of an alkali metal into water, it will react violently as it forms a compound Na & K- essential part of our diet Control movement of fluid, transmit nerve impulses, control muscles

Group 2 Alkaline Earth Metals 2 valence electrons- close cousins of the alkali metal group Added electron makes them slightly less reactive Still not found as free elements in nature Examples: Be- used to harden metal alloys Mg- medicinal purposes, fireworks Ca- used for structural purposes in people and buildings

Groups 3-12 Transition Elements Sometimes called subgroups- have either 1 or 2 electrons in the outer shell Most have similar properties Strong metals Iron Triad- iron, cobalt, & nickel Common uses: metal mixtures (alloys) Sterling silver- copper, silver, gold Gold in jewelry- gold, silver, copper

Inner Transition Metals The periodic tables usually isn’t shown with the inner transition elements positioned where they should be to save space. Lanthanides- atomic #s –Uses: produce colors for TV and movies Actinides- atomic #s –All are radioactive and unstable –Uses: glass for camera lenses and nuclear reactors

Nonmetals 1.Hydrogen and the elements on the right side of the table (17 of them) 2.Hold electrons tightly Are more likely to take electrons from metals than give them up 3.At room temp, most are gases and some are brittle solids 4.Do not conduct heat and electricity well

Group 17 Halogens Have 7 valence electrons Very reactive chemically (WHY???) Very distinct properties that change with the atoms’ size As atomic # increases, elements get denser, color gets darker, phase changes occur Very dangerous in strong concentrations Chlorine used as poisonous gas in WWI Useful in weaker concentrations: Cl- kills germs F- prevents tooth decay I essential nutrient (hyperthyroidism)

Group 18 Noble Gases 8 valence electrons- outermost energy level is full! Very nonreactive- allows them to exist in nature as pure substances Uses: Neon & Argon- neon lights Helium- balloons & blimps Krypton- light in lasers

Metalloids 1. Have both metallic and nonmetallic properties 2.A heavy line divides the metals and nonmetals on the right-hand side of the table 3.Semiconductors- between a conductor and an insulator  can be controlled Without semiconductors, we would not have watches, pocket calculators, or microcomputers

Group 13 The Boron Group Have 3 valence electrons Contains metalloids- elements that have both metal and nonmetal characteristics Can form covalent and ionic bonds Ex: Boron Aluminum- most abundant metal in earth’s crust Used in pots and pans

Group 14 Carbon Group Allotropes- different forms of the same element (different molecular structures) SiliconSilicon: occurs as two allotropes 1.A hard, gray substance 2.A brown powder CarbonCarbon: 1.Diamond- clear and extremely hard - each carbon atom is bonded to four other carbon atoms 1.Graphite- a black powder - Each carbon atom is bonded to three other carbon atoms

Group 14 Carbon Group Have 4 valence electrons Few other similarities- Group contains nonmetals, metalloids, and metals Uses: Carbon- occurs in coal, oil, natural gas, and foods Tin- coat other metals to prevent corrosion Included in bronze and pewter alloys Lead- used to be used in paint Silicon- 2 nd most abundant element in Earth’s crust Main component in semiconductors

Group 15 Nitrogen Group Have 5 valence electrons Elements tend to share electrons Make covalent compounds Uses: Nitrogen- abundant in air and human bodies Phosphorus- fertilizer, match heads Antimony & Bismuth- used with other metals to lower melting points

Group 16 Oxygen Group Have 6 valence electrons Most share electrons when they bond Diatomic molecules- consist of two atoms of the same element in a covalent bond Uses: Oxygen- needed for respiration Sulfur- pigments in paint Selenium- multivitamins, copy machines