Atoms, Molecules, and Ions   Ch. 2 (cont.)

Note: Placement of elements 58 – 71 and 90 – 103 saves space 11/9/2018

Some important classifications: A groups = representative elements or main group elements I A = alkali metals II A = alkaline earth metals VII A = halogens VIII = noble gases B groups = transition elements Inner transition elements = elements 58 – 71 and 90 – 103 58 – 71 = lanthanide elements 90 – 103 = actinide elements 11/9/2018

Metals, nonmetals, and metalloids Note: groups IIIA-VIA contain all 3 classifications 11/9/2018

Metals Nonmetals Metalloids Tend to shine (have metallic luster) Can be hammered or rolled into thin sheets (malleable) and can be drawn into wire (ductile) Are solids at room temperature (except for Hg) Conduct heat & electricity Form alloys Nonmetals Lack the properties of metals Exception: graphite form of carbon conducts electricity React with metals to form (ionic) compounds React with other nonmetals to form molecular (covalent) compounds May be solid, liquid, or gas Metalloids Have properties between metals and nonmetals Conduct electricity but not as well as metals (semiconductors) Most elements are metals, slightly over a dozen are nonmetals, and only a handful are metalloids. 11/9/2018

Tungsten (W)- a metal greyish-white lustrous metal solid at room temperature highest melting point (3400°C) and lowest vapor pressure of all metals at temperatures over 1650°C has the highest tensile strength used as filaments that glow white-hot in electric light bulbs 11/9/2018

Carbon (C)- a nonmetal diamond graphite 11/9/2018

Silicon (Si)- a metalloid Being able to switch electrical conductivity “on” and “off” is the basis of a transistor Solid state electronics Computers, stereos, TV receivers, VCRs, CD players, and AM-FM radios rely on transistors made from semiconductors 11/9/2018

Group 1A – Alkali Metals 11/9/2018

Group 1A – Alkali Metals Properties: VERY REACTIVE Na in water Properties: VERY REACTIVE - never found free in nature - react with water to form H2 and alkaline solution - react with halogens (e.g. X = chlorine) to produce MX (e.g. NaCl) 11/9/2018

Group 2A – Alkaline Earth Metals 11/9/2018

Group 2A – Alkaline Earth Metals Properties: VERY REACTIVE - never found free in nature - react with water to form H2 and alkaline solutions (except Be) - react with oxygen to form MO - react with halogens (e.g. chlorine) to produce MX2 (e.g. MgCl2) 11/9/2018

Group 3A 11/9/2018

Group 3A Properties: 1 metalloid (boron) and 4 metals - react with oxygen to form M2O3 - react with halogens (e.g. chlorine) to produce MX3 (e.g. BCl3) - Al is most abundant metal in the earth’s crust Bauxite, Al2O3 11/9/2018

Group 4A 11/9/2018

Group 4A 1 non-metal, 2 metalloids, 2 metals - react with oxygen to form XO2 (e.g. CO2) - carbon is the basis for organic and biochemistry - Si common in minerals and used in microelectronics 11/9/2018

Group 5A 11/9/2018

Group 5A - 2 non-metals, 2 metalloids, 1 metal - react with oxygen to form oxides - nitrogen is 80% atmosphere - N and P important in living organisms - As is a poison - Bi is heaviest non-radioactive element; used in PeptoBismol 11/9/2018

Group 6A – The Chalcogens 11/9/2018

Group 6A – The Chalcogens - 3 non-metals, 1 metalloid, 1 metal - highly reactive - react with oxygen to form XO2 and XO3 - oxygen is 20% atmosphere and is involved in most biological energy sources - S and Se are poisonous but need trace amounts for life 11/9/2018

Group 7A – the Halogens 11/9/2018

Group 7A – the Halogens All non-metals Highly reactive… react with alkali metals to produce salts like NaCl 11/9/2018

Group 8A –The Noble Gases 11/9/2018

Group 8A – The Noble Gases - least reactive elements - not that abundant on earth - after H, He is the most abundant element in the universe - ‘neon’ signs - Lighter than air balloons 11/9/2018

Group B – Transition Metals 11/9/2018

Group B – Transition Metals all metals wide variety of chemical reactivity seldom found free in nature; except Ag, Au, Pt. important commercial materials includes lanthanides and actinides (e.g., U) 11/9/2018

Compounds Essentially all elements combine to form compounds Compounds are of two types: Molecular, which involve shared electrons and consist of electrically neutral, discrete particles called molecules Ionic compounds, which involve electron transfer and charged particles called ions, do not exist as discrete molecular units 11/9/2018

Chemical formulas are collections of chemical symbols that are used to describe elements and compounds Free elements are not combined with other elements in a compound Fe (iron), Na (sodium), and K (potassium) Many nonmetals occur as diatomic molecules H2, N2, O2, F2, Cl2, Br2, I2 11/9/2018

Phosphorus, P4 Sulfur, S8 11/9/2018

Chemical formulas specify the composition of a substance NaCl is composed of the elements sodium and chlorine in a one-to-one (atom) ratio Fe2O3 is composed of the elements iron and oxygen in a two-to-three ratio CO(NH2)2 expands to CON2H4, but there are good reasons to write some compounds with parentheses Hydrates are crystals that contain water molecules, for example plaster: CaSO4 • 2H2O When all the water is removed (by heating), the solid that remains is said to be anhydrous (without water) When to use subscripts, parentheses, and dots 11/9/2018

Terminology Elements Compounds Molecular Ionic Acids Bases Free elements Diatomics P4 and S8 Compounds Molecular Ionic Acids Bases 11/9/2018

A diatomic molecule contains only two atoms A molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds H2 H2O NH3 CH4 A diatomic molecule contains only two atoms H2, N2, O2, Br2, HCl, CO A polyatomic molecule contains more than two atoms O3, H2O, NH3, CH4 2.5 11/9/2018

cation – ion with a positive charge An ion is an atom, or group of atoms, that has a net positive or negative charge. cation – ion with a positive charge If a neutral atom loses one or more electrons it becomes a cation. Na 11 protons 11 electrons Na+ 11 protons 10 electrons anion – ion with a negative charge If a neutral atom gains one or more electrons it becomes an anion. Cl- 17 protons 18 electrons Cl 17 protons 17 electrons 2.5 11/9/2018

A monatomic ion contains only one atom Na+, Cl-, Ca2+, O2-, Al3+, N3- A polyatomic ion contains more than one atom OH-, CN-, NH4+, NO3- 2.5 11/9/2018

How many protons and electrons are in Do You Understand Ions? How many protons and electrons are in Al 27 13 ? 3+ 13 protons, 10 (13 – 3) electrons How many protons and electrons are in Se 78 34 2- ? 34 protons, 36 (34 + 2) electrons 2.5 11/9/2018

Common monoatomic ions 2.5 11/9/2018