Chemistry: Atomic Structure

Front 1

Believed that particles could be divided until a basic particle that cannot be broken down further is reached

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Democritus

Front 2

Democritus called the particle the ____ from the Greek word meaning ___________

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atom; indivisible

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Aristotle did not believe in _____. He thought matter was __________.

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atoms; continuous

Front 4

Aristotle's views were held by many people and set back the development of chemistry for nearly ____ _____

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2000 years

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Neither Democritus or Aristotle's view was supported by __________ ________

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scientific research

Front 6

Chemists accepted the idea of an _______ as a substance that cannot be further broken down by ordinary chemical means

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element

Front 7

Accepted that elements combine to form _________ that have different ________ and ________ __________ than the elements that formed them

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compounds; chemical & physical properties

Front 8

Controversy over whether or not elements always combine in the same _____ to form compounds

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ratio

Front 9

The emphasis on __________ ________ of chemical reactions led to new laws ending the controversy

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quantitative analysis

Front 10

Improved ________ helped them measure the masses of elements and compounds studied

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balances

Front 11

Mass is neither destroyed nor created during ordinary chemical reactions or physical changes

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Law of Conservation of Mass

Front 12

A chemical compound contains the same element in exactly the same proportions by mass regardless of the size of the sample or the source of the compound

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Law of Definite Proportions

Front 13

If two or more different compounds are composed of the same 2 elements, then the ratio of the masses of the 2nd element combined with a certain mass of the 1st element is always in a ratio of small whole numbers

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Law of Multiple Proportions

Front 14

Explained the 3 new laws

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Dalton's Atomic Theory

Front 15

All matter is composed of extremely small particles called _____

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atoms

Front 16

Atoms of a given element are identical in ____, ____, and _____ __________ while atoms of different elements differ in ____, ____, and _____ __________

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size, mass and other properties

Front 17

Atoms cannot be __________, _______, or _________

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subdivided, created or destroyed

Front 18

Atoms of different elements combine in simple ____ ______ ______ to form chemical compounds

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whole number ratios

Front 19

In chemical reactions, atoms are ________, _________, or __________

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combined, separated or rearranged

Front 20

Dalton's Atomic Theory:

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- All matter is composed of extremely small particles called atoms.
- Atoms of a given element are identical in size, mass and other properties while atoms of different elements differ in size, mass and other properties.
- Atoms cannot be subdivided, created or destroyed
- Atoms of different elements combine in simple whole number ratios to form chemical compounds.
- In chemical reactions, atoms are combined, separated or rearranged

Front 21

Dalton's Theory modified to explain new ____________

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observations

Front 22

Today we know that atoms are made of _______, ________, and _________

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protons, neutrons, and electrons

Front 23

A given element has ________ so the mass of individual atoms of the element can vary

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isotopes

Front 24

Statements of Modern Atomic Theory include:

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- All matter is made up of small structures called atoms.
- Atoms of the same element are chemically alike while atoms of different elements are chemically different.
- Since elements have isotopes, individual atoms of an element may not all have the same mass. However, the atoms of the naturally occurring isotopes of every element have a characteristic average atomic mass.
- Individual atoms of different elements may have nearly identical masses. However, the atoms of different natural elements have different average atomic masses.
- Atoms are not subdivided in chemical reactions.
- Nucleus does not change.
- electrons are lost, gained or shared

Front 25

All matter is made up of small structures called _____

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atoms

Front 26

Atoms of the same element are chemically _____ while atoms of different elements are chemically _________

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alike; different

Front 27

Since elements have isotopes, individual atoms of an element may not all have the same ____. However, the atoms of the naturally occurring isotopes of every element have a characteristic

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mass; average atomic mass

Front 28

Individual atoms of different elements may have nearly identical ______. However, the atoms of different natural elements have different _______ ______ ______

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masses; average atomic masses

Front 29

Atoms are not subdivided in ________ _________. _______ does not change. Electrons are ____, ______, or ______

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chemical reactions; Nucleus; lost, gained or shared

Front 30

The smallest particle of an element that keeps the chemical properties of that element

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ATOM

Front 31

Two regions of an atom are the _______ and ________ _____

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nucleus & electron cloud

Front 32

Subatomic particles:

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- protons
- neutrons
- electrons

Front 33

Resulted from investigations into the relationship between matter and electricity

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Discovery of Atomic Structure

Front 34

observed that objects can have a positive or negative charge and that like charges repel while unlike charges attract

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Ben Franklin

Front 35

1st to realize that an atom's structure is related to electricity

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Michael Faraday

Front 36

In the discovery of atomic structure, a _______ ___ ____ was used

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cathode ray tube

Front 37

tube containing a ___ at ___ ________

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gas; low pressure

Front 38

___________ is passed through the tube and the gas in the tube _____

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electricity; glows

Front 39

Scientists hypothesized that a stream of _________ caused the glow

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particles

Front 40

They called the stream _______ ____

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cathode rays

Front 41

JJ Thomson showed that the cathode rays are made of identical __________ _______ _________, later called _________

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negatively charged particles; electrons

Front 42

Robert Millikan confirmed that electrons are ________. He also showed that the mass of electron is ____ x __^__g

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negative; 9.11 x 10^-28g

Front 43

Since cathode rays have the same properties regardless of the gas used or the metal used to make the cathode, it was concluded that _________ are present is all types of ________

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electrons; elements

Front 44

Scientists proposed different ______ of the atom over time

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models

Front 45

The plum-pudding model was devised by __ ________. He described the atom as neutral with the same number of ________ charges stuck in a ball of ________ charges like _____ in ____-_______

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JJ Thomson; negative; positive; plums in plum-pudding

Front 46

The Planetary Model was devised by __________. He compared an atom to a _____ ______ with _________ moving about the _______ like ________ around the ___

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Rutherford; solar system; electrons; nucleus; planets around the sun

Front 47

There were 3 reasons the planetary model was discarded:

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- Since unlike charges attract, the electrons would crash into the nucleus.
- Since like charges repel, the nucleus would
fly apart.
- If there were too many electrons on the same path around the nucleus, they would crash into each other

Front 48

The Bohr Model was devised by _____ ____

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Neils Bohr

Front 49

The Bohr Model is similar to the _________ _____

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planetary model

Front 50

Said that electrons with a specific amount of ______ moved in a particular _____

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energy; orbit

Front 51

Also said that only a certain number of _________ fit in a particular _____

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electrons; orbit

Front 52

Schrodinger Model also called the _______ __________ _____

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Quantum Mechanical Model

Front 53

Current atomic model devised by ___________

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Schrodinger

Front 54

Describes the atom as a _______ surrounded by an
________ _____

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nucleus; electron cloud

Front 55

Electrons move around the _______ in regions of _____ based on the amount of ______ the electrons hold. No precise ______

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nucleus; space; energy; orbits

Front 56

The nucleus was discovered by __________ & his associates

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Rutherford

Front 57

gold foil experiment showed that the nucleus is ________ & an atom is mostly _____

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positive; space

Front 58

Used _____ _________ as bullets striking a thin piece of ____ ____

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alpha particles; gold foil

Front 59

Most protons went through proving that an atom is ______ _____. Some particles were deflected slightly while others were greatly deflected. Since like charges repel, Rutherford concluded that the nucleus of the atom is ________

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mostly space; positive

Front 60

The nucleus is the location of the atom's ________ ____

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greatest mass

Front 61

The nucleus has a ________ charge

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positive

Front 62

The nucleus is the _____ and _____ central portion of an atom

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small & dense

Front 63

The nucleus is composed of _______ and ________ except in the simplest hydrogen atom which only has _ ______

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protons & neutrons; 1 proton

Front 64

Protons are ________ and have a mass of _____ x __^__g. Discovered by _________. Have a mass number of _. Have an electric charge of __

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positive; 1.673 x 10^-24g; Goldstein; 1; +1

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Neutrons are _______ & have a mass of ____ x __^___g. Discovered by ________. Have a mass number of _. Have an electric charge of _

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neutral; 1.675 x 10^-24g; Chadwick; 1; 0

Front 66

The number of _______ in an atom's nucleus determines its ________

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protons; identity

Front 67

nuclear forces are the short range forces between _______ and _______, _______ and ________, and ________ and ________ that hold the nucleus together

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protons & protons, protons & neutrons, and neutrons & neutrons

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only occur when the particles in the nucleus are extremely _____ ________

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close together

Front 69

do not occur _______ the nucleus

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outside

Front 70

Provides volume for an atom

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Electron Cloud

Front 71

a cloud of ________ charge. made of _________

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negative; electrons

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electrons have a mass of ____ x __^___g. have a mass number of _. have an electric charge of __

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9.11 x 10^-28g; 0; -1

Front 73

electrons that have similar energy move around in the same ______ ______ or ______ ______

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energy levels or energy shells

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_ energy levels

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7

Front 75

each energy level has a:

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maximum # of electrons it can hold

Front 76

Rutherford and & Bohr were the first to say _________ ____ __ __ ____

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electrons move in an atom

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Atoms are electrically _______

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neutral

Front 78

positive charge = negative charge or the number of _______= the number of ________

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protons; electrons

Front 79

Atoms are very _____

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small

Front 80

______ ______ is the distance from the center of the nucleus to the the outer part of the electron cloud

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Atomic radius

Front 81

Atomic radii range in size from __ to ___pm

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40 to 270 pm

Front 82

The radii of atomic nuclei are about _.___pm

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0.001 pm

Front 83

Atomic nuclei also have a density of about _ x __^_ metric tons/cm^3

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2 x 10^8 metric tons/cm3

Front 84

the number of protons in the nucleus of an atom

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atomic number ( Z)

Front 85

Atoms of different elements have different:

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atomic numbers or numbers of protons

Front 86

On the periodic table, the atomic number is the _____ _____ ______ usually written __ ___ __ the element's symbol

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small whole number; on top of

Front 87

________ are arranged according to increasing atomic number from left to right on the Periodic Table

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Elements

Front 88

The atomic number identifies the _______

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element

Front 89

Since atoms are electrically neutral, the atomic number also tells us the number of _________ in the atom

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electrons

Front 90

atoms of the same element that have different masses

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Isotopes

Front 91

isotopes have the same number of _______ and _________

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protons & electrons

Front 92

isotopes have different numbers of ________

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neutrons

Front 93

most elements are a mixture of ________

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isotopes

Front 94

hydrogen has _ ________

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3 isotopes

Front 95

isotopes have similar ________ __________ because they have the same number of protons

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chemical properties

Front 96

A _______ is a general term for any isotope of any element

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nuclide

Front 97

the total number of protons & neutrons in the nucleus of an isotope

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Mass number (A)

Front 98

the mass number is written after the Element name or symbole of the isotope

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hyphen notation

Front 99

If we know A & Z, then we know the number of _______ and ________

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protons and neutrons

Front 100

Number of electrons = _ and the number of neutrons = _-_

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Z; A-Z

Front 101

Actual mass of an atom is very _____

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small

Front 102

Mass of a proton is _____ x __^___g

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1.673 x 10^-24g

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Mass of a neutron is _____ x __^___g

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1.675 x 10^-24 g

Front 104

Mass of an electron is ____ x __^___g

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9.11 x 10^-28g

Front 105

Scientists have set up a ________ to compare all atomic masses to the element ______-__

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standard; Carbon-12

Front 106

Scientist have set up a relative scale so that the mass of 1 atom of _-__ is equal to __ ___ OR _ ___ = 1/12 the mass of a C-12 atom

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C-12; 12 amu; 1 amu

Front 107

Used proportions to figure out the ________ ______ ____ for each element

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relative atomic mass

Front 108

the mass of an atom expressed relative to the C-12 scale where the mass of one Carbon-12 atom = 12 amu

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relative atomic mass

Front 109

The units of the carbon-12 relative mass scale are amu or ______ ____ _____

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atomic mass units

Front 110

the sum of the protons & neutrons in the nucleus of an atom OR the whole number closest to the relative atomic mass of the isotope

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Mass number

Front 111

Most elements occur naturally as a mixture of ________

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isotopes

Front 112

The percentage of each isotope in a sample of elements is nearly always ___ ____ no matter where the sample is taken. this percentage is called the _________ for each isotope

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the same; abundance

Front 113

the weighted average of the relative atomic masses of the naturally occurring isotopes of an element

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average atomic mass

Front 114

Average where some components carry more __________ than others

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importance

Front 115

Average atomic mass is calculated using a ________ _______

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weighted average

Front 116

There are no units for ______ ______ on the Periodic Table

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atomic weight

Front 117

Average atomic mass is taken one step further:

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Divide the average atomic mass by 1 amu so the units are gone

Front 118

ratio of the average atomic masses of the naturally occurring isotopes of an element to 1 amu

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Atomic weight