The Periodic Table

1. The Periodic Table Section 1- Organizing the Elements Section 2- Exploring the Periodic Table Section 3- Families of Elements

2. State Standards • CLE 3202.1.3 Characterize and classify elements based on their atomic structure • CLE 3202.Inq.1 Recognize that science is a progressive endeavor that reevaluates and extends what is already accepted • CLE 3202.Inq.6 Communicate and defend scientific findings

3. 1 - Organizing The Elements • KEY QUESTIONS : • How did Mendeleev arrange the elements in his periodic table? • How are elements arranged in the modern periodic table?

4. Mendeleev - Recognizing Patterns • By 1860, 60+ elements were known • Dmitri Mendeleev, Russian Chemist, studied properties of the elements • 1869 : he published first Periodic Table of Elements • Arranged by rows of increasing mass number • If chemical properties repeated, new row started • EXAMPLE : Lithium and Sodium are very reactive • Gold and Silver have similar properties, same column

5. Predicting New Elements • Gaps existed in his table - ? • Predicted the properties of Germanium • Description close to what was later found to be Ge • He was the first to use table to predict • Work in Progress – Some predictions did not fit • Te and I fit better in a an inconsistent way • i.e, where the mass number decreased from left - right

6. Changing the Arrangement • Mendeleev’s Periodic Table has been improved • Henry Moseley, ~ 1910 • Elements arranged by atomic number • Resolved problems such as at Tellurium – Iodine • Te has larger average mass, I has 1 more proton • They fit in rows/columns BETTER THAT WAY

7. Mendeleev’s Competition • John Newlands, 1865, Law of Octaves • Every 8th element will mimic each other in The Table • Ordered by Atomic Weights (YET ANOTHER ‘MASS’) • Ridiculed and DISS’ED ( dismissed by peers )

8. Periodic Law • Metallic properties decrease across PERIODS • Other properties such as reactivity and conductivity • GROUPS have similar properties • Groups – Columns • Periods - Rows • Elements with similar properties appear at regular intervals – The Periodic Law

9. Let’s Describe Some Elements!! • The chemical symbol, C, stands for carbon, which has an atomic number of 6 and an atomic mass [ OR, MASS NUMBER ] of 12.01 • Which value is an average ( average of what? ) • Which value also represents molar mass? • Your turn!!

10. Let’s Describe Some Elements!! The chemical symbol, C, stands for carbon, which has an atomic number of 6 and an atomic mass [ OR, MASS NUMBER ] of 12.01

11. KEY QUESTIONS : • How did Mendeleev arrange the elements in his periodic table? • How are elements arranged in the MODERN periodic table?

12. 2 –Exploring the Periodic Table • KEY QUESTIONS : • Why do elements within a group of the Periodic Table have similar chemical properties? • What happens to an atom that gains or loses electrons? • What are the three main categories of elements?

13. Role of Electrons • How many electrons in a neutral atom? • Trends in PT are result of electron arrangement • Valence electrons account for similar properties • Example: Lithium and Sodium • Element’s location related to electron arrangement

14. Ion Formation • What is an “ion”? • Once an atom gains/loses electrons, it no longer has a balance between protons/electrons • Charges don’t cancel  atom has net electric charge • What is easier – GAIN or LOSE electrons? • Group 1 elements form positive ions ( CATIONS ) • Group 17 elements form negative ions ( ANIONS )

15. Classifying Elements • Elements in each category have similar properties • Metals • Nonmetals • Semiconductors

16. 2 –Exploring the Periodic Table • KEY QUESTIONS : • Why do elements within a group of the Periodic Table have similar chemical properties? • What happens to an atom that gains or loses electrons? • What are the three main categories of elements?

17. 3 –Families of Elements • KEY QUESTIONS : • What does each element family have in common? • What are the families of metals? • What are some non-metal families? • What are semiconductors

18. Let’s Classify Elements Further • Relate GROUPS of elements to “family” • Elements in family have same # valence electrons • ONLY elements ( not compounds ) are in a family

19. Metals • INCLUDE: Alkali, Alkaline-Earth, and Transition • Alkali metals are very reactive ( Li and Na ) • Alkaline-Earth metals also fairly reactive • Form compounds found in human body/limestone • More solid than Group 1 • Means: harder, denser, higher melting temperature • Transition metals – less reactive than Group 1-2 • Typically more solid than Group 1-2

20. Transition Metals • Very good catalysts • Catalyst : speeds a reaction up / is not reacted • H2 and O2 explode in presence of Pt catalyst • Some synthetic elements • Technetium and Promethium • Radioactive (nuclei decays into smaller atoms) • Atomic Number > 92 : elements are SYNTHETIC

21. Nonmetals • Families include Noble Gases and Halogens • NOBLE GASES: Group 18 ( Ne, Ar, He) • HALOGENS: Group 17 ( Cl, F, Br ) • Combine easily with metals to form SALTS • Nonmetals/compounds plentiful on Earth • Carbon – backbone of life ( organic compounds ) • C forms many other compounds

22. Semiconductors • Also called metalloids • B, Si, Ge, As, Sb, Te • Able to CONDUCT heat and electricity • BUT only under certain conditions • Silicon ( Si ) is found everywhere!! • Boron ( B ) used in steel and glass

23. Hydrogen • Hydrogen is in a class by itself • 1 proton and 1 electron • Reacts with many other elements • Most abundant element in universe • 3 out of every 4 atoms in universe are H

24. 3 –Families of Elements • KEY QUESTIONS : • What does each element family have in common? • What are the families of metals? • What are some non-metal families? • What are semiconductors