Elements, Atoms, and the Periodic Table

1. Elements, Atoms, and the Periodic Table Unit Objectives: Identify the names, symbols and origin of chemical elements; Appreciate relative abundance of various elements; Identify the different kinds of elements represented in the periodic table; Recognize the major properties used to distinguish the different types of elements; Appreciate the historical development of the atomic theory; Explain and describe the atomic structure of elements and how it relates to their individual properties Created by C. Ippolito September 2006

2. Elements: Ancient and Modern Theory • Robert Boyle • 1661 - “The Sceptical Chymist” • Element • Substance that cannot be broken into simpler substances • Compound • Formed when two or more elements combine • Antoine Lavoisier (1743-1794) • 1789 – “Elementary Treatise on Chemistry” • Identified 33 “elements” Created by C. Ippolito September 2006

3. Chemical Symbols • alchemists used secret codes • signs for known elements • shorthand used to represent elements • JJ Bersalius • each element is represented a one or two letter symbol with the first letter always capitalized • symbol derived from first letter of name, if already assigned take a second letter from name Created by C. Ippolito September 2006

4. English named aluminum (Al) argon (Ar) arsenic (As) carbon (C) calcium (Ca) Honorary named Curium (Cm) Californium (Cf) Latin named gold [aurum] (Au) iron [ferrum] (Fe) lead [plumbum] (Pb) mercury [hydragyrum] (Hg) silver [argentum] (Ag) sodium [natrium] (Na) tin [stannum] (Sn) German named tungsten [wolfram] (W) Chemical Names and Symbols Created by C. Ippolito September 2006

5. Abundant and Rare Elements • 11 elements form 99% of earth crust • - oxygen • - silicon • - aluminum • - iron • - calcium • - sodium • - potassium • - magnesium • - hydrogen • - titanium • - chlorine Created by C. Ippolito September 2006

6. Periodic Table of Elements • metals • metalloids • nonmetals Created by C. Ippolito September 2006

7. Organization of Periodic Table • Rows • form periods • Columns • form groups or families • Classroom Table • RED • gaseous elements • BLUE • liquid elements • BLACK • solid elements Created by C. Ippolito September 2006

8. Metals • Physical Properties – solid, except Hg • Conductivity • good conductors of heat and electricity • Luster • shiny surface • Malleability • may be hammered or rolled • Ductility • may be drawn into wires • Hardness • varies • hard – Cr, Fe, Mn • soft – Au, Pb, Na Created by C. Ippolito September 2006

9. Nonmetals • Physical Properties – solid, liquid, gas • Conductivity • poor conductors of heat and electricity • Luster • NO, dull surface • Malleability • NO, brittle – crumble when hit • Ductility • NO • Hardness • NO • carbon (diamond) exception Created by C. Ippolito September 2006

10. Metalloids • some properties like metals others like nonmetals • semiconductors Created by C. Ippolito September 2006

11. Early Atomic Structure • Democritus • Atomic Theory of Matter • all matter could be divided into tiny indivisible particles called atoms • different types of atoms existed for each different type of material • not based on experimental evidence • Aristotle • Continuous Theory of Matter • all matter was continuous and always could be divided into smaller parts without end Created by C. Ippolito September 2006

12. Law of Conservation of Mass • Antoine Lavoisier • Father of Modern Chemistry • quantitatively measured mass of reactants and compared it with mass of products • found mass remained constant • Law of Conservation of Mass • matter can be changed but cannot be created nor destroyed • combustion combines elements with oxygen Created by C. Ippolito September 2006

13. Law of Definite Proportions • Joseph Proust • regardless of where a substance came from or how large the sample • specific substances always contained elements in the same ratio by mass • Law of Definite Proportions Created by C. Ippolito September 2006

14. Dalton’s Atomic Theory • John Dalton • postulates to explain Lavoisier’s and Proust’s findings • Matter made of small particles (atoms) • Atoms are indestructible. Cannot be created or destroyed in chemical or physical changes. • Atoms of same element are identical, have the same mass. • Atoms of different elements are different, have different mass • Compounds form by combining atoms of different elements Created by C. Ippolito September 2006

15. Parts of the Atom • in the late 1800’s experiments show that atoms are made of smaller particles • Elementary or Subatomic Particles • proton – positive charge, mass = 1 amu, in nucleus • electron – negative charge, mass = 1/1837 amu, outside nucleus • neutron – neutral charge, mass = 1 amu, in nucleus Created by C. Ippolito September 2006

16. Elements and Isotopes • Isotope • atoms of the same element that have different mass • same atomic number • same number of protons and electrons • same behavior • mass differs because the atoms have different numbers of neutrons • Isotopes of Hydrogen • Protium 11H • Deuterium 21H • Tritium 31H Created by C. Ippolito September 2006

17. Atomic Masses • for an individual atom is a whole number • atomic mass = # of protons + # of neutrons • for an element it is the average of the atomic masses of all existing isotopes • in periodic table it is a decimal value • Calculation of Element Atomic Mass • (isotope mass)x(abundance) = mass contribution • add mass contributions of all isotopes • resulting sum is the average atomic mass Created by C. Ippolito September 2006

18. Mole • the mole is a fixed amount of particles • 1 mole = 6.022 x 1023 pieces • this number is N or Avogadro’s Number • named in honor of an Italian chemist • the concept of the mole allows us to set up a relationship between the immeasurable masses of atoms (in amu) and measurable amounts of a substance (in grams) • 1 mole of amu’s = 1 gram Created by C. Ippolito September 2006