Chapter 4 Atoms and Elements - Nina Rodriguez - … · TN Ch 4.1-4.2 Date Title and Highlight Topic: ... discovery of the atom Ch 4.1-4.2 READ Ch 4.1-4.2 ... Chapter 4 Atoms and Elements

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THE ATOM


TN Ch 4.1-4.2 Date

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Summary Questions:

Write Book Question out and answer it

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TN Ch 4.1-4.2

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DRAW ANY PICTURES, FIGURES,

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LEAVE SPACES SO WE CAN ANSWER

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LEFT Side – PICTURES, PRACTICE PROBLEMS, ETC


TOPIC: ATOMIC THEORY

EQ: Explain the history & the discovery of the atom

Ch 4.1-4.2

READ Ch 4.1-4.2 (pg. 93-95) first then write notes


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.


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)


CH 4.2

The Atom: From Philosophical Idea to Scientific Theory


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.


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.


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.


WHY?

• In the end….. Aristotle was wrong in the end.

Aristotle favored

the earth, fire, air

and water

approach to the

nature of matter.


DALTON’S ATOMIC THEORY • John Dalton (1766-1844)

• 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!


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!!

http://tm.ask.com/r?t=c&s=p&sv=0a30052b&uid=0BC1ACC9982C64134&sid=3444474eb444474eb&o=0&id=30751&p=/fr&u=http://www.juliantrubin.com/imagesc/dalton1.gif


• 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!!!

Dalton’s Atomic Theory


FLAWS OF DALTON’S THEORY…

#2. Atoms of a given element are identical in size, mass, and other properties.

#3. Atoms cannot be subdivided, created, or destroyed.

Isotopes – atoms with the same

number of protons but a different

number of neutrons

Subatomic particles – electrons,

protons, neutrons, and more


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)

RIGHT side - End of notes


TOPIC: SUBATOMIC PARTICLES

EQ: Explain the history & the discovery of the 3 subatomic particles in an atom

Ch 4.3

READ Ch 4.3 (pg. 95-97) first then write notes


CH 4.3 - 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.


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.


Electric Current Electric Current

Draw this with

notes in color!!!


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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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)


THOMSON’S PLUM PUDDING ATOMIC MODEL

Thomson believed that the electrons were like plums

embedded in a positively charged “pudding,” thus it

was called the “plum pudding” model.

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notes in color!!!


• 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.


Millikan’s Oil Drop

Experiment

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 10-28 g

004_MILLIKANOIL.MOV


RUTHERFORD’S GOLD FOIL EXPERIMENT • 1911 - 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)


RUTHERFORD’S FINDINGS • Most of the

negatively charged particles passed through the gold foil without changing course.

• Some of the negatively charged particles did bounce away from the gold sheet as if they had hit something solid.

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notes in color!!!


(1) Most of the atom is more or less ______ _______.

(2) The nucleus is very _________ and ___________.

(3) The nucleus is ______________ 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”

empty space

dense tiny

positively


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 charge-neutral.

Draw this with

notes in color!!!


Rutherford’s Model of

the Atom

2.2

Draw this with

notes!!!


James Chadwick (1932)

Discovered the neutron. The neutron has about the same mass as

the proton.


• 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!


Democristus

400BC

Aristotle

4 elements

Dalton (1803)

Atomic Theory

Thomson (1897)

Plum Pudding Model

Cathode Ray Tube

electrons

Rutherford (1911)

Gold Foil Experiment

Proton & Nucleus (Mass and Volume)

Millikan (1909)

Charge & Mass

of electron

Chadwick (1932)

Neutron

THE ATOM - TIMELINE Draw this left

side!!!







TOPIC: THE STRUCTURE OF THE ATOM

EQ: What is the difference between protons, neutrons, and electrons?

Ch 4.4



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 1022)

Copper


THE STRUCTURE OF THE ATOM

• The atom is composed of two main regions: the nucleus & the electron cloud.


THE ATOM

• The atom is made up of three subatomic particles.

Draw this with

notes in

color!!!


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 = no


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.

electron = e-

The electron cloud is

composed of electrons.


SUBATOMIC PARTICLES Particle Symbol Location Electrical

charge

Mass

(amu)

Actual

Mass (g)

Electron e- Outside

nucleus

-1 1/1840 9.11x10-28

(About 2000

times smaller

than Proton

and neutron)

Proton p+

Nucleus +1 1

1.67x10-24

Neutron n0

nucleus 0 1

1.67x10-24

They have the SAME Mass

Draw this left

side!!!


PRACTICE PROBLEMS #1

What are the two main regions of the atom?

What is the charge on the nucleus?

left side!!!







TOPIC: ELEMENT NAMES, SYMBOLS, & THE STRUCTURE OF THE ATOM

EQ: How do you write an element’s symbol? How many p+, no, & e- does

any element have?

Ch 4.5



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 ______________.

• The next letter is _______________.

capitalized

lowercase


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


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


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

NUMBERS.


• 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.


SYMBOL NOTATION

X Mass

number

Atomic

number Subscript →

Superscript →


Atomic number (Z).

Protons determines the identity of the element.

A# = p+ = e- (atoms are neutral)

The Mass Number (A),

(rounded to the nearest

integer)

Mass# = p+ + no

A is always the larger number than Z.

# of neutrons = mass number – # p+


LOOK FOR THE ELEMENT CHLORINE…..

LET’S WRITE HIS CHEMICAL SYMBOL

NOTATION


Cl 35

17

MASS

NUMBER

ATOMIC

NUMBER

NUMBER OF

PROTONS

# PROTONS +

# NEUTRONS

Symbol notation


LOOK FOR THE ELEMENT CARBON…..

LET’S WRITE HIS CHEMICAL SYMBOL

NOTATION


SYMBOL NOTATION

Element followed by a hyphen – mass#

Carbon-12


• 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 – 63.546

• Mass number - 64


PRACTICE PROBLEMS

Element Atomic

#

Mass

#

p + n o e - Symbol

Oxygen - 8

33 42

-31 31 15

91 140

Sodium - 23

Uranium - 238

80

Br

35

26

Mass number

left side







TOPIC: ISOTOPES

EQ: What is an isotope and how does it affect the atom?

Ch 4.8



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


ISOTOPES


EXAMPLE OF AN ISOTOPE

Cl 35

17 Cl 37

17

20 NEUTRONS

ATOMIC MASS

18 NEUTRONS

ATOMIC NUMBER


Review…. How to write Symbol Notation


Practice Problem #1

Circle which of the following are isotopes.

40

20 X 40

18 X 42

20 X 40

19 X 43

20 X

left side!!!


Practice Problem #1

Determine the number of protons, neutrons and electrons in the neutral (non-charged) isotopes of the following atoms:

88

38Sr 84

38Sr

left side!!!







TOPIC: AVERAGE ATOMIC MASS

EQ: How do you calculate average atomic mass?

Ch 4.9



Average Atomic Mass


• The atomic masses listed in the Periodic Table are a “weighted average” of all the isotopes of the element.

• Units = atomic mass unit (amu)


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.)


• All elements have their own unique percent natural abundance of isotopes.

• Naturally occurring chlorine consists of

75.77% chlorine-35 (mass 34.97 amu) and 24.23% chlorine-37 (mass 36.97 amu).

• Which isotope is the most abundant?

• What is the Average Atomic Mass of Cl?


• Gallium has two naturally occurring isotopes: Ga-69, with mass 68.9256 amu and a natural abundance of 60.11%, and Ga-71, with mass 70.9247 amu and a natural abundance of 39.89%. Calculate the atomic mass of gallium.

Left side: Leave 5 lines of space to solve in class


• Write Question #97

Left side: Leave 5 lines of space to solve in class


SUMMARY QUESTIONS: CH 4 #26




Documents

Chapter 4 Atoms and Elements - Nina Rodriguez - … · TN Ch 4.1-4.2 Date Title and Highlight Topic: ... discovery of the atom Ch 4.1-4.2 READ Ch 4.1-4.2 ... Chapter 4 Atoms and Elements