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Grade 9 Science Unit 1: Atoms, Elements, and Compounds

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1 Grade 9 Science Unit 1: Atoms, Elements, and Compounds
Chapter 2: Elements are the building blocks of matter.

2 Elements A pure substance that cannot be broken down or separated into simpler substances. Made up of one kind of atom. More than 115 elements known about 92 occur naturally. Bill Nye Video: Atoms and Elements Read the Did you Know on page 38, add details of Marie Curie’s life Brass is an alloy of Marie Curie. Working with her new husband, Pierre, Curie found that certain kinds of rocks poured out constant and extraordinary amounts of energy, yet without diminishing in size or changing in any detectable way. What she and her husband couldn’t know—what no one could know until Einstein explained things the following decade—was that the rocks were converting mass into energy in an exceedingly efficient way. Marie Curie dubbed the effect “radioactivity.” In the process of their work, the Curies also found two new elements—polonium, which they named after her native country, and radium. In 1903 the Curies and Becquerel were jointly awarded the Nobel Prize in physics. (Marie Curie would win a second prize, in chemistry, in 1911, the only person to win in both chemistry and physics.) For a long time it was assumed that anything so miraculously energetic as radioactivity must be beneficial. For years, manufacturers of toothpaste and laxatives put radioactive thorium in their products, and at least until the late 1920s the Glen Springs Hotel in the Finger Lakes region of New York (and doubtless others as well) featured with pride the therapeutic effects of its “Radioactive mineral springs.” Radioactivity wasn’t banned in consumer products until By this time it was much too late for Madame Curie, who died of leukemia in Radiation, in fact, is so pernicious and long lasting that even now her papers from the 1890s—even her cookbooks—are too dangerous to handle. Her lab books are kept in lead-lined boxes, and those who wish to see them must don protective clothing. Consider doing activity 2-1A Meet the Elements on page 39! The only magnetic metals are iron, cobalt and nickel

3 Chemical Symbols One or two (sometimes 3) letters used to represent an element name Standard throughout the world Examples: O = Oxygen Au = Gold

4 Note: If there is only one Letter in the chemical symbol it is always CAPITALIZED If there are two letters, the FIRST IS CAPITALIZED the second is lower case Example: H = Hydrogen He = Helium Use the example of CO versus Co to help illustrate this, group the 20 need to knows by either One letter that is the first letter of the name, two letters which are either the name or name is matched in another language

5 Hydrogen Iron Sodium Nickel Potassium Copper Magnesium Zinc Calcium
Use Your Periodic Table on page 50 to Identify the Chemical Symbols of these 20 Need to Know Elements: Hydrogen Iron Sodium Nickel Potassium Copper Magnesium Zinc Calcium Carbon

6 Nitrogen Silicon Oxygen Silver Neon Gold Helium Mercury Chlorine Lead
You could play CHEMO or pick a letter from the alphabet and find elements that start with that letter Hydrogen gas demo on page 44 with the burning splint Read Copper section of Wild Weird and Wonderful on page 46 You could do a game where I pick an element and students have to guess who I am by clues that I give. Questions page 47 #1-4, *17c

7 The Periodic Table Organizes elements according to their physical and chemical properties. Developed by Dmitri Mendeleev in 1867. odd and crazed-looking professor at the University of St. Petersburg named Dmitri Ivanovich Mendeleyev. Mendeleyev (also sometimes spelled Mendeleev or Mendeléef) was born in 1834 at Tobolsk, in the far west of Siberia, into a well-educated, reasonably prosperous, and very large family—so large, in fact, that history has lost track of exactly how many Mendeleyevs there were: some sources say there were fourteen children, some say seventeen. All agree, at any rate, that Dmitri was the youngest. Luck was not always with the Mendeleyevs. When Dmitri was small his father, the headmaster of a local school, went blind and his mother had to go out to work. Clearly an extraordinary woman, she eventually became the manager of a successful glass factory. All went well until 1848, when the factory burned down and the family was reduced to penury. Determined to get her youngest child an education, the indomitable Mrs. Mendeleyev hitchhiked with young Dmitri four thousand miles to St. Petersburg—that’s equivalent to traveling from London to Equatorial Guinea—and deposited him at the Institute of Pedagogy. Worn out by her efforts, she died soon after. Mendeleyev dutifully completed his studies and eventually landed a position at the local university. There he was a competent but not terribly outstanding chemist, known more for his wild hair and beard, which he had trimmed just once a year, than for his gifts in the laboratory. However, in 1869, at the age of thirty-five, he began to toy with a way to arrange the elements. At the time, elements were normally grouped in two ways—either by atomic weight (using Avogadro’s Principle) or by common properties (whether they were metals or gases, for instance). Mendeleyev’s breakthrough was to see that the two could be combined in a single table. Mendeleyev was said to have been inspired by the card game known as solitaire in North America and patience elsewhere, wherein cards are arranged by suit horizontally and by number vertically. Important that he lefts spaces for elements yet to be discovered, true value of the table not realized until after his death

8 Includes the element’s name, symbol, atomic number and atomic mass.

9 ATOMIC NUMBER = # of Protons (& Electrons in a Neutral atom)
ATOMIC MASS = Average mass of the atoms of an element

10 MASS NUMBER = the number of Protons + the number of Neutrons = The ROUNDED atomic Mass WHY?

11 To find the Number of Neutrons:
Subtract the Atomic number from the rounded Atomic Mass! 8 O Bi # Neutrons = =8 15.999

12 Complete the Chart: K 12 8 2 23.0 hydrogen Element Name Symbol
Atomic Number # of Protons # of Electrons Atomic Mass K hydrogen 12 8 2 23.0 Don’t do Activity 2-2A

13 Elements Metals Metalloids Non-Metals Make note of the “staircase” learn to recognize a known metal to tell which side of the periodic table a metal appears on. Text Page 51

14 Elements can be METALS, NON-METALS, or METALLOIDS
Shiny Malleable Ductile Usually solid Good conductors of heat and electricity

15 Non-metals Tend to be gases or brittle solids Dull
Not malleable or ductile Poor conductors of heat and electricity Tell story from the refinery

16 May conduct electricity
Metalloids Poor conductors of heat Non- malleable and not ductile Solids Shiny or dull May conduct electricity Properties of both metals and non-metals.

17 The periodic table is organized into periods and chemical families.
Periods: the horizontal rows Families: the vertical columns Elements in the same family have similar physical and chemical properties. See video clips on YouTube: Periodic Table of Videos You could watch the video on the organization of the periodic table, highlight the noble gases, read the Science Watch on page 65. What element is located in Period __ Family ____

18 Chemical Families Li, Na, K … Alkali Metals: Family 1
Highly reactive with halogens Reactive with oxygen and water Low melting points Soft Video

19 Alkaline Earth Metals: Family 2
Produce bright flames React with water Less reactive then alkali metals Burn in air if heated Be, Mg, Ca…

20 Halogens: Family 17 F, Cl, Br… Non-metals Highly reactive
F is the most reactive element

21 Noble Gases: Family 18 Very stable Highly unreactive All gases
He, Ne, Ar…

22 Transition Metals Found at the centre of the periodic table
Complex arrangement of electrons Three are magnetic; Fe, Co and Ni

23 Families of the Periodic Table
See table on page 56 which shows a picture of each element. See also page 58 for a different version of the periodic table. All Families are shown on page 52 of your text.

24 Questions page 59 #’s 1-14

25 Section 2.3 The Periodic Table and the Atomic Theory page 60 Bohr-Rutherford diagram
Nucleus 2e- 8e- 18e- Energy level diagrams represent the Energy of the Electrons not a path of the electron motion. The further out the electron the more energy associated with it.

26 Electron Filling Rules: - Use the ATOMIC NUMBER to determine the number of electrons and protons of the element - Levels are filled from the INNER most energy levels OUT. - The First Energy level can hold a MAXIMUM of 2 electrons - The second and third energy levels hold a MAXIMUM of 8 electrons

27 Energy Level Periodic Trends
The number of Valence Electrons = the Family Number The number of Energy Levels = the Period Number The Maximum Number of Electrons in each Level = the Number of elements in that Period Elements in the same Family have the same number of Valence Electrons

28 The valence shell of the noble gases is FULL; therefore stable.
Gaining or losing electrons will allow atoms to achieve a kind of stability. Metals will lose electrons while non-metals will gain them. Consider the special case of Hydrogen, see the “PAUSE AND REFLECT” on page 67

29 Questions Page 67 #1-14 These may be done in small groups or assign groups a number to do and write the correct answer on the board.

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