Chapter 5 The Periodic Table

1. Chapter 5 The Periodic Table

2. 5.1 Organizing the Elements

3. Antoine Lavoisier • In 1779 this French chemist categorized elements into four types: • Metals • Non-metals • Gases • Earths • For 80 years, scientists looked for a better organizing principle for all elements……

4. Dmitri Mendeleev • This Russian chemist found the answer. • Realized in the 1800’s that there was a pattern to the elements. • 63 known elements existed at the time. • Wrote each element’s name and properties on cards.

5. Mendeleev • Subatomic particles (protons, neutrons, electrons) had not been discovered. • So he arranged according to the atomic mass. • He arranged elements into rows in order of increasing mass so that elements with similar properties were in the same column.

6. Problem with Mendeleev’s Table Some heavier elements were placed ahead….. ……….of lighter elements.

7. What do the dashes represent? Why are masses listed with some of the elements, but not with all of them?

8. Mendeleev left blanks in his table for undiscovered elements. • He knew what their properties would be and left locations or ‘parking spots’ for them. • Proof of a model being correct is whether or not it can be used to predict. • The blanks in his table were eventually filled with elements whose properties he predicted.

9. He named undiscovered elements within a group after known elements within it. • Eka-aluminum • This is the name he gave to the element found just one spot below aluminum. • He predicted its eka-aluminum’s properties based upon the trend within the rest of the group. • It would be a soft metal with a low melting point and a density of 5.9 g/cm3. • In 1875, a new metal with nearly these identical properties was discovered. • Eka-aluminum then was said to beGallium. • 1st time that it proved useful and not the only time.

10. 5.2 The Modern Periodic Table Mendeleev’s Periodic table arranged elements in order of increasing _________. His Periodic table pre-dates protons discovery. The modern Periodic table arranges elements in order of increasing __________. See p. 131. Why is the Modern Periodic table not shown in the book as it is on this page?

11. PERIOD ROW C O L U M N F A M I L Y G R O U P

12. 18 columns or groups • 7 rows or periods • Periodic Law • Properties of the elements are a function of their atomic number. • The two bottom rows shown on the bottom of the Periodic table are called the ‘Rare Earth’ elements. • Lanthanide series named after Lanthanum. • Actinide series named after Actinium.

13. 1 Atomic Number H Atomic symbol Hydrogen Element name 1.0079 Average Atomic Mass The average atomic mass of an element is a weighted average of all the isotopes of an element. Every element has many different forms with not any single form being more correct than the other.

14. Atomic mass units • amu • Since a amu is 1/12 the mass of an isotope of C-12. • Why C-12 ??? A very common atom and the most abundant isotope of carbon. • The average atomic mass of an element is calculated by multiplying each of its isotopes % abundance by its’ mass and then adding them all together.

15. Classes of Elements • Divided in 3 ways • Physical state • Solid • Liquid • Gas • Natural or artificial • Elements 1-92 occur naturally • > 92 are man-made • Properties • Metals • Non-metals • Metalloids

16. Elements exist in 3 states: -solids -liquids -gases Solids are represented inblack. Liquids are represented in purple. Gases are represented in red. Non-metals are represented with an orange square; Metals with a blue square and Metalloids with a greensquare.

17. Metals • Conduct heat &__________ • Nearly always solid (except Hg) • Malleable (aka bendable) • Ductile (can be drawn into a thin wire) • Somevery reactive • Transition metals • Groups 3 – 12 • Some of the 1st elements found were from this group. • Form brightly colored compounds

18. Non-metals • Properties are the opposite of those of metals. • Non-metals can be found in all 3 phases. • Some non-metals are very reactive while others are not. • Metalloids • Show a combination of the properties of metals and non-metals.

19. Variation across a period • Elements are most metallic on the left and become less as move to the right. • More non-metallic on the right. Metallic------->-------------->-----------------> Non-metallic • The metals in Group 1 are the most reactive of all metals. • The non-metals in Group 17 are the most reactive of all non-metals.

20. 5.3 Representative Elements • Periodic Table labeled in 2 ways… • 1A – 8A & 1B-10B • 1 -18 • The A’s are a reminder that the # before it equals the # of valence e- for its group. • Group 1A elements have 1 valence electron. • Valence electrons are those found the greatest distance away from the nucleus.

21. Elements in the same family have similar properties because they have the same number of valence electrons.

22. Alkali metals • ? valence electron in each. • Extremely reactive, _____ metals. • Always found in nature combined with other elements. • Elements at the top of this group are less reactive than those at the bottom. • Hydrogen is found here, but isn’t really a real member.

23. Alkaline Earth Metals • ? valence electrons • Harder than alkali metals. • Less reactive than alkali metals. • Be is not reactive; Ca, Ba, Sr react w/ cold H2O; Mg reacts only with hot water. • Mg & Ca are important for our health.

24. Boron family • ? valence electrons • Named after 1st element in family. • All its’ elements have ? valence electrons. • Aluminum best known of family. • Most abundant metal in Earth’s crust. • Very light, strong metal. • Boron (B) is a metalloid; the others _____.

25. Carbon group • 4 valence electrons • 1 non-metal (___________) • 2 metalloids (__________ & __________) • 2 metals (________ & ________) • Carbon is the ‘life’ element. • Silicon is the 2nd most abundant element in the crust of planet.

26. Nitrogen family • 5 valence electrons • 2 non-metals (______ & ______) • 2 metalloids (_______ & _______) • 1 metal (_____) • Nitrogen makes-up 78% of air. • Human body & fertilizers • Phosphorus has multiple allotropes. • White phosphorus is dangerous; illegal military weapon. • Red phosphorus used in match heads.

27. Oxygen family • ? valence electrons • 3 non-metals (______, ______ & ______) • 2 metalloids (______ & ______) • Oxygen is the most abundant element in the Earth’s crust. • 21% of all air is oxygen.

28. Halogens • ?valence electrons • Halogen means ‘salt forming’. • __non-metals & __ metalloid • Most reactive non-metals. • Just as reactive as Alkali metals. • Fluorine is the most reactive • Top elements most reactive, bottom least.

29. Noble gases • Aka ‘Inert gases’ • ? Valence electrons (except He) • Colorless • Odorless • Very un-reactive • Many of them have industrial uses.