THE ATOM Pearson Education, Inc.

Transcription

1 THE ATOM

2 Title and Highlight Right Side NOTES ONLY TN Ch Topic: EQ: Date Reflect Question: Reflect on the material by asking a question (its not suppose to be answered from notes) NOTES: Write out the notes from my website. Use different types of note-taking methods to help you recall info (different color pens/highlighters, bullets, etc) When I lecture we will add more info, so leave spaces in your notes Summary Questions: Write Book Question out and answer it (in another color based on what you read from my notes or textbook. THESE ARE AT THE VERY END OF NOTES

3 Title and Highlight LEFT Side PICTURES, PRACTICE PROBLEMS, ETC TN Ch DRAW ANY PICTURES, FIGURES, AND WRITE OUT ANY PRACTICE PROBLEMS/QUESTIONS. WE WILL ANSWER THEM TOGETHER. LEAVE SPACES SO WE CAN ANSWER QUES.

4 Ch TOPIC: ATOMIC THEORY EQ: Explain the history & the discovery of the atom READ Ch (pg ) first then write notes

5 CH 4.1 ATOMS Atoms are incredibly small. To get an idea of how small atoms are: if every atom within a small pebble were the size of the pebble itself, the pebble would be larger than Mount Everest.

6 ATOMS AND ELEMENTS ATOM - Building Blocks of Matter An atom is the smallest particle of an element that retains the chemical properties of that element. An element is a substance that cannot be broken down into simpler substances. There are about 91 different elements in nature, and consequently about 91 different kinds of atoms. (The other 27 are synthetic man made elements)

7 CH 4.2 The Atom: From Philosophical Idea to Scientific Theory

8 THE EARLY ATOM As early as 400 B.C., Democritus called nature s basic particle the atomon based on the Greek word meaning indivisible. His theory: Matter could not be divided into smaller pieces forever, eventually the smallest possible piece would be obtained.

9 ATOMS To Democritus, atoms were small, hard particles that were all made of the same material but were different shapes and sizes. Atoms were infinite in number, always moving and capable of bonding together.

10 THE EARLY ATOM Most influential philosopher, Aristotle rejected Democritus atom theory b/c different from his ideas Criticized Democritus idea that atoms moved through empty space Aristotle succeeded Democritus and did not believe in atoms. Instead, he thought that all matter was continuous. It was his theory that was accepted for the next 2000 years.

11 Aristotle favored the earth, fire, air and water approach to the nature of matter. WHY? In the end.. Aristotle was wrong in the end.

12 DALTON S ATOMIC THEORY John Dalton ( ) English Chemist and schoolteacher In 1808,performed a number of experiments that led to the idea of atoms..over 2000 years later after Democritus/Aristotle theory. I was a school teacher at the age of 12!

13 DALTON S ATOMIC THEORY 1. All matter is composed of extremely small particles called atoms. 2. Atoms of a given element are identical in size, mass, and other properties.** 3. Atoms cannot be subdivided, created, or destroyed.** 4. Atoms of different elements combine in simple whole-number ratios to form chemical compounds. 5. In chemical reactions, atoms are combined, separated, or rearranged. **Today, we know these parts to be wrong!!

14 Dalton s Atomic Theory Was Dalton s theory a huge step toward our current model of matter? Yes!!! It was a breakthrough in our understanding of matter. Was all of Dalton s theory accurate? No!!!

15 FLAWS OF DALTON S THEORY #2. Atoms of a given element are identical in size, mass, and other properties. Isotopes atoms with the same number of protons but a different number of neutrons #3. Atoms cannot be subdivided, created, or destroyed. Subatomic particles electrons, protons, neutrons, and more

16 RIGHT side - End of notes SUMMARY QUESTIONS: CH 4 #1-2 Number BQ and write it out Answer it (in another color/highlight it based on what you read from my notes or textbook)

17 Ch 4.3 TOPIC: SUBATOMIC PARTICLES EQ: Explain the history & the discovery of the 3 subatomic particles in an atom READ Ch 4.3 (pg ) first then write notes

18 CH DISCOVERY OF THE SUBATOMIC PARTICLES The discovery of the subatomic particles came about from the study of electricity & matter. Benjamin Franklin s kite experiment in 1752 demonstrated that lightning was electrical.

19 DISCOVERY OF THE ELECTRON 1870 s - many experiments were performed in which electric current was passed through gases at low pressures These experiments were carried out in glass tubes called cathode-ray tubes.

20 Draw this with notes in color!!! Electric Current Electric Current

21 DISCOVERY OF THE ELECTRON The rays traveled from cathode (negative) to anode (positive). Negatively charged objects deflected the rays away. Therefore, it was determined that the particles making up the cathode rays were negatively charged.

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23 THOMSON S PLUM PUDDING MODEL In 1897, the English scientist J.J. Thomson provided the first hint that an atom is made of even smaller particles. (1908 Nobel Prize in Chemistry)

24 THOMSON S PLUM PUDDING ATOMIC MODEL Draw this with notes in color!!! Thomson believed that the electrons were like plums embedded in a positively charged pudding, thus it was called the plum pudding model.

25 So.. J. J. Thomson discovered the electron. found that e- are negatively charged. e- are much smaller and lighter than atoms. every element (atom) has e-. He proposed that atoms must contain + charge that balanced the - charge of electrons.

26 Robert Millikan (1909): Millikan s Oil-drop Experiment Discovered the mass and charge on the electron Charge of electron: -1 Mass of electron = 9.1 x g Millikan s Oil Drop Experiment

27 RUTHERFORD S GOLD FOIL EXPERIMENT English physicist Ernest Rutherford Rutherford s experiment involved firing a stream of tiny positively charged alpha particles at a thin sheet of gold foil (2000 atoms thick)

28 Most of the negatively charged particles passed through the gold foil without changing course. RUTHERFORD S FINDINGS Some of the negatively charged particles did bounce away from the gold sheet as if they had hit something solid. Draw this with notes in color!!!

29 (1) Most of the atom is more or less empty. space (2) The nucleus is very tiny and. dense (3) The nucleus is positively charged due to protons. (4) The nucleus (protons and neutrons) is 99.97% of an atom s mass. (5) The electron cloud = majority of volume SO. atoms is neutral: the positive (nucleus) balances out the negative electrons So, why do electrons stay surrounded around the nucleus? Opposites attract

30 A SUMMARY OF THE NATURE OF ELECTRICAL CHARGE Positive and negative electrical charges attract each other. Positive positive and negative negative charges repel each other. Positive and negative charges cancel each other so that a proton and an electron, when paired, are chargeneutral. Draw this with notes in color!!!

31 Rutherford s Model of the Atom Draw this with notes!!! 2.2

32 Discovered the neutron. James Chadwick (1932) The neutron has about the same mass as the proton.

33 After the proton & electron was discovered. The Neutron was discovered last (almost 30 years later) out of all the subatomic particles, why? Scientist knew the charge of nucleus (+) and knew the mass of nucleus (came from proton). But their calculations were off by half. could not figure out why the nucleus was so heavy if the proton only had a certain mass. There must be a third subatomic particle that weighed as much as a proton, but with no charge!

34 Draw this left side!!! THE ATOM - TIMELINE Dalton (1803) Atomic Theory Rutherford (1911) Gold Foil Experiment Proton & Nucleus (Mass and Volume) Democristus 400BC Aristotle 4 elements Thomson (1897) Plum Pudding Model Cathode Ray Tube electrons Millikan (1909) Charge & Mass of electron Chadwick (1932) Neutron

35 RIGHT side - End of notes SUMMARY QUESTIONS: CH 4 #3-4 Number BQ and write it out Answer it (in another color/highlight it based on what you read from my notes or textbook)

36 Ch 4.4 TOPIC: THE STRUCTURE OF THE ATOM EQ: What is the difference between protons, neutrons, and electrons? READ Ch 4.4 (pg ) first then write notes

37 THE ATOM Atom - the smallest particle of an element. How small is an atom? Copper atoms in penny 29,000,000,000,000,000,000,000 (2.9 x ) Copper

38 THE STRUCTURE OF THE ATOM The atom is composed of two main regions: the nucleus & the electron cloud.

39 The atom is made up of three subatomic particles. THE ATOM Draw this with notes in color!!!

40 NUCLEUS OF AN ATOM Nucleus- VERY small region located at the center of the atom. The nucleus accounts for most of an atoms mass but very little volume, making it a very dense region. The nucleus contains protons & neutrons. proton = p + neutron = n o

41 ELECTRON CLOUD OF AN ATOM The electron cloud is the negatively charged region of the atom that accounts for most of the atom s volume but very little of the atom s mass. The electron cloud is composed of electrons. electron = e -

42 Draw this left side!!! SUBATOMIC PARTICLES Particle Symbol Location Electrical charge Mass (amu) Actual Mass (g) Electron e - Outside nucleus Proton p + Nucleus / x10-28 (About 2000 times smaller than Proton and neutron) 1.67x10-24 Neutron n 0 nucleus x10-24 They have the SAME Mass

43 left side!!! PRACTICE PROBLEMS #1 What are the two main regions of the atom? What is the charge on the nucleus?

44 RIGHT side - End of notes SUMMARY QUESTIONS: CH 4 #5-7 Number BQ and write it out Answer it (in another color/highlight it based on what you read from my notes or textbook)

45 Ch 4.5 TOPIC: ELEMENT NAMES, SYMBOLS, & THE STRUCTURE OF THE ATOM EQ: How do you write an element s symbol? How many p +, n o, & e - does any element have? READ Ch 4.5 (pg ) first then write notes

46 CH 4.5: CHEMICAL SYMBOLS Chemists use chemical symbols to represent elements. The chemical symbol consists of 1 or 2 letters. The first letter ALWAYS. capitalized The next letter is. lowercase

47 CH 4.5 ELEMENTS: ORIGINS OF THE NAMES OF THE ELEMENTS Most chemical symbols are based on the English name of the element. Some symbols are based on Greek or Latin names, which include the following: potassium K kalium sodium Na natrium lead Pb plumbum mercury Hg hydrargyrum iron Fe ferrum silver Ag argentum tin Sn stannum copper Cu cuprum

48 JUST READ!!!! Early scientists gave newly discovered elements names that reflected their properties: Argon, from the Greek argos, means inactive, referring to argon s chemical inertness. Other elements were named after countries: Polonium after Poland Francium after France Americium after the United States of America. Other elements were named after scientists. Curium after Marie Curie Einstenium after Albert Einsten

49 THE PERIODIC TABLE OF THE ELEMENTS LISTS ALL KNOWN ELEMENTS ACCORDING TO THEIR ATOMIC NUMBERS.

50 The # of protons in the nucleus of an atom that identifies an element. The # of protons in the nucleus of an atom is its atomic number.

51 SYMBOL NOTATION Superscript Subscript Mass number Atomic number X

52 The Mass Number (A), (rounded to the nearest integer) Mass# = p + + n o # of neutrons = mass number # p + Atomic number (Z). Protons determines the identity of the element. A# = p + = e - (atoms are neutral) A is always the larger number than Z.

53 LOOK FOR THE ELEMENT CHLORINE.. LET S WRITE HIS CHEMICAL SYMBOL NOTATION

54 MASS NUMBER ATOMIC NUMBER Symbol notation # PROTONS + # NEUTRONS 35 Cl 17 NUMBER OF PROTONS

55 LOOK FOR THE ELEMENT CARBON.. LET S WRITE HIS CHEMICAL SYMBOL NOTATION

56 SYMBOL NOTATION Element followed by a hyphen mass# Carbon-12

57 Difference between Mass and Atomic weight Atomic weight is the weight of all the isotopes for that element (decimal #) Mass number is the rounded number for the atomic weight. Example: Copper Atomic weight Mass number - 64

58 left side Element Atomic # Mass # Oxygen - 8 Mass number Sodium - 23 PRACTICE PROBLEMS p + n o e - Symbol Uranium Br

59 RIGHT side - End of notes SUMMARY QUESTIONS: CH 4 #8-10 Number BQ and write it out Answer it (in another color/highlight it based on what you read from my notes or textbook)

60 Ch 4.8 TOPIC: ISOTOPES EQ: What is an isotope and how does it affect the atom? READ Ch 4.8 (pg ) first then write notes

61 4.8 ISOTOPES: WHEN THE NUMBER OF NEUTRONS VARIES All atoms of an element have the same # of protons. They do not have the same # of neutrons. Atoms with the same # of protons but different # of neutrons are called isotopes. Example Hydrogen

62 ISOTOPES

63 EXAMPLE OF AN ISOTOPE ATOMIC MASS 35 Cl 37 Cl NEUTRONS 20 NEUTRONS ATOMIC NUMBER

64 Review. How to write Symbol Notation

65 left side!!! Practice Problem #1 Circle which of the following are isotopes. 40 X 40 X 42 X 40 X 43 X

66 left side!!! Practice Problem #1 Determine the number of protons, neutrons and electrons in the neutral (non-charged) isotopes of the following atoms: Sr Sr

67 RIGHT side - End of notes SUMMARY QUESTIONS: CH 4 #22-25 Number BQ and write it out Answer it (in another color/highlight it based on what you read from my notes or textbook)

68 Ch 4.9 TOPIC: AVERAGE ATOMIC MASS EQ: How do you calculate average atomic mass? READ Ch 4.9 (pg ) first then write notes

69 Average Atomic Mass

70 The atomic masses listed in the Periodic Table are a weighted average of all the isotopes of the element. Units = atomic mass unit (amu)

71 In general, atomic mass is calculated according to the following equation: Average Atomic mass = Step 1: Convert the percent natural abundances into decimal form by dividing by 100. Step 2: Multiply the decimal abundances with the isotopes mass. Step 3: Add up the atomic masses for each isotope. This is the average atomic mass for that element (should be close to the number listed on P.T.)

72 All elements have their own unique percent natural abundance of isotopes. Naturally occurring chlorine consists of 75.77% chlorine-35 (mass amu) and 24.23% chlorine-37 (mass amu). Which isotope is the most abundant? What is the Average Atomic Mass of Cl?

73 Left side: Leave 5 lines of space to solve in class Gallium has two naturally occurring isotopes: Ga-69, with mass amu and a natural abundance of 60.11%, and Ga-71, with mass amu and a natural abundance of 39.89%. Calculate the atomic mass of gallium.

74 Left side: Leave 5 lines of space to solve in class Write Question #97

75 RIGHT side - End of notes SUMMARY QUESTIONS: CH 4 #26 Number BQ and write it out Answer it (in another color/highlight it based on what you read from my notes or textbook)