Text A Chemistry 1.2 Developing Atomic Theories Flashcards
(168 cards)
1
Q
What is the main function of a linear accelerator?
A
To fire fast-moving particles into a target surrounded by sensitive detectors
Linear accelerators help scientists probe inside tiny particles of matter by splitting them apart.
2
Q
According to Dalton, what was the atom?
A
A solid, uniform sphere
Dalton’s view of the atom was foundational to early atomic theory.
3
Q
During which centuries did scientists improve laboratory techniques for isolating pure substances?
A
1600s and 1700s
17th and 18th centuries
4
Q
What did scientists observe consistently that led to the generalization of scientific laws?
A
An action or condition
Consistent observations led to the formulation of scientific laws.
5
Q
What hypothesis was developed to explain several early scientific laws?
A
Matter is made up of tiny particles
6
Q
Who was John Dalton?
A
An English scholar and teacher who published a comprehensive atomic theory in 1808
7
Q
What was the heart of Dalton’s atomic theory?
A
Every substance is made up of indivisible atoms
8
Q
What key difference did Dalton propose between atoms of different elements?
A
Their mass
9
Q
What law did Dalton’s atomic theory help explain regarding mass during chemical reactions?
A
The total mass of substances before and after a reaction is always the same
This supports the idea that particles are rearranged but not created or destroyed.
10
Q
List three key points of Dalton’s atomic theory.
A
- All matter is made up of small particles called atoms.
- Atoms cannot be created, destroyed, or divided into smaller particles.
- All atoms of the same element are identical in mass and size, but different from atoms of other elements.
11
Q
True or False: Dalton’s theory stated that atoms of different elements are identical in mass and size.
A
False
12
Q
What are compounds formed from?
A
Atoms of different elements combining in fixed proportions.
13
Q
What do the tiniest particles of any compound contain?
A
The same types and relative numbers of atoms.
14
Q
Do chemical reactions change the atoms themselves?
A
No, they change the way atoms are grouped.
15
Q
What was a basis for many of Dalton’s conclusions?
A
Assumptions.
16
Q
What was Dalton’s incorrect assumption about water?
A
That the formula for water was OH.
17
Q
What did Joseph Proust’s measurements indicate about water?
A
It contains eight times more oxygen by mass than hydrogen.
18
Q
What mass did Dalton assign to hydrogen?
A
One unit.
19
Q
Based on Dalton’s assumption, what mass would an atom of oxygen have?
A
Eight units.
20
Q
What did Dalton develop to track his assumptions about atoms?
A
A system of symbols.
21
Q
What were some of Dalton’s inaccurate assumptions about compounds?
A
The composition of water and other compounds.
22
Q
What did Dalton predict about nitrogen and oxygen?
A
There should be several different compounds, including NO, NO2, and NO3.
23
Q
What technological achievement improved Dalton’s theory?
A
The refinement of the gas discharge tube.
24
Q
What is a gas discharge tube?
A
A sealed glass vessel containing a gas at low pressure.
25
What are cathode rays?
Rays produced in gas discharge tubes when electricity flows through the gas.
26
Who improved the gas discharge tube in 1855?
Heinrich Geissler.
27
What is Daltonism?
Color-blindness, specifically to red.
28
What did ancient Greek philosophers speculate about the universe?
That it must be composed of small particles that could not be broken down.
29
What term did ancient Greek philosophers use to describe indivisible particles?
Atomos.
30
Did ancient Greek thinkers use experimental investigation to develop their ideas?
No.
31
True or False: Dalton's predictions about compounds were later verified experimentally.
True.
32
Fill in the blank: Dalton's calculations of relative masses were inaccurate due to _______.
Incorrect assumptions.
33
What did experiments with gas discharge tubes suggest about matter?
Matter contains tiny particles that have negative charges
## Footnote
This inference led to the discovery of electrons.
34
What was the scientific consensus at the end of the nineteenth century regarding Dalton's atomic theory?
Many scientists were reluctant to abandon Dalton's atomic theory
## Footnote
Dalton's theory proposed that atoms are indivisible.
35
What did scientists not want to believe about Dalton's indivisible atoms?
That they might actually be made up of even smaller particles
## Footnote
This reluctance hindered acceptance of the concept of subatomic particles.
36
True or False: The concept of electrons was widely accepted at the end of the nineteenth century.
False
## Footnote
Many scientists were hesitant to accept the existence of subatomic particles.
37
Fill in the blank: Experiments with gas discharge tubes led to the inference that matter contains tiny particles with _______.
negative charges
38
What did experiments with gas discharge tubes suggest about matter?
Matter contains tiny particles that have negative charges
## Footnote
This inference led to the discovery of electrons.
39
What was the scientific consensus at the end of the nineteenth century regarding Dalton's atomic theory?
Many scientists were reluctant to abandon Dalton's atomic theory
## Footnote
Dalton's theory proposed that atoms are indivisible.
40
What did scientists not want to believe about Dalton's indivisible atoms?
That they might actually be made up of even smaller particles
## Footnote
This reluctance hindered acceptance of the concept of subatomic particles.
41
True or False: The concept of electrons was widely accepted at the end of the nineteenth century.
False
## Footnote
Many scientists were hesitant to accept the existence of subatomic particles.
42
Fill in the blank: Experiments with gas discharge tubes led to the inference that matter contains tiny particles with _______.
negative charges
43
Who used a new version of the gas discharge tube in 1894 to provide evidence of cathode rays?
J. J. Thomson
44
What type of particles did J. J. Thomson demonstrate were present in cathode rays?
Negatively charged particles
45
What apparatus did Thomson modify to obtain evidence about cathode rays?
Gas discharge tube
46
What was the outcome of Thomson's experiments regarding the relationship between charge and mass?
He found a quantitative relationship between charge and mass.
47
What are the negatively charged particles discovered by Thomson now known as?
Electrons
48
What is the mass of each electron compared to a hydrogen atom?
Less than the mass of a single hydrogen atom
49
What happens to cathode rays when a positively charged plate is placed near the tube?
The ray is attracted to the positive plate.
50
Fill in the blank: Thomson concluded that matter contained _______ charged particles.
negatively
51
Did J. J. Thomson initially have many believers in the existence of particles smaller than atoms?
No
52
What did Thomson say about a distinguished physicist's reaction to his lecture on electrons?
He thought Thomson had been 'pulling their legs.'
53
What does a 'neon' sign represent in terms of gas discharge tubes?
A modern version of a gas discharge tube
54
What determines the color of a neon sign?
The gas inside the tube
55
What color is emitted by a tube that contains neon gas?
Red
56
What gas glows violet-blue in a discharge tube?
Argon
57
When was the neon tube invented?
Not specified in the text
58
Where did the first neon sign appear?
Not specified in the text
59
Who is sometimes called 'the father of the electron'?
J.J. Thomson
## Footnote
Thomson published results in 1897 referring to cathode ray particles as corpuscles.
60
What term did G. Johnstone Stoney invent in 1891?
Electron
## Footnote
He used it to describe a unit of charge in electrolysis experiments.
61
What did George Fitzgerald argue about electrons and corpuscles?
They were the same thing.
62
What is the charge of an electron?
Negatively charged.
63
What did scientists conclude about the presence of electrons?
Every atom contained electrons.
64
What must each atom contain to balance the negative charge of electrons?
A source of positive charge.
65
Who first suggested a model of the atom that included a positive charge cloud?
William Thomson (Lord Kelvin).
66
What is the Thomson model of the atom also known as?
Plum-pudding or raisin-bun theory.
67
What did Ernest Rutherford discover about radioactive elements?
They emitted three different types of emissions: alpha particles, electrons, and gamma rays.
68
Where did Ernest Rutherford teach from 1898 until 1907?
McGill University in Montreal.
69
What significant experiment did Rutherford conduct in 1909?
He probed the structure of atoms using alpha particles and gold foil.
70
What unexpected result did Rutherford observe in his gold foil experiment?
A small number of alpha particles bounced back from the gold foil.
71
Fill in the blank: The Thomson atomic model of 1903 viewed the atom as a positively charged sphere embedded with sufficient numbers of _______.
Electrons.
72
What did the Thomson model fail to account for?
The emission of alpha particles.
73
How much more massive are alpha particles compared to electrons?
About 7200 times.
74
What type of particles does polonium emit?
Alpha particles
## Footnote
Polonium is a radioactive element known for emitting alpha particles.
75
What happens to a fluorescent screen when struck by an alpha particle?
It lights up
## Footnote
Fluorescent screens are used in various experiments to detect alpha particles.
76
How do alpha particles interact with electrons in gold foil?
They are not significantly deflected
## Footnote
Alpha particles are much more massive than electrons, leading to minimal deflection.
77
What did Rutherford reason about the deflection of alpha particles?
Effects of many random deflections would cancel each other
## Footnote
This reasoning led to the conclusion that overall deflection would be minimal.
78
What did Rutherford's observations lead him to develop?
A new atomic theory
## Footnote
This theory included both electrons and positively charged particles.
79
What did Rutherford conclude about the atoms in the foil?
They must possess something very dense and intensely positive
## Footnote
This conclusion was based on the observed rebounds of alpha particles.
80
What did most alpha particles do when passing through the gold foil?
Went straight through
## Footnote
This observation indicated that most of the positive alpha particles were not deflected.
81
What did Rutherford suggest about the 'dense positive something' in the atoms?
It must be relatively small
## Footnote
The small size was inferred because most alpha particles passed through the foil without deflection.
82
In what year did Hantaro Nagaoka propose an atomic model similar to Rutherford's?
1904
## Footnote
Nagaoka's model described a disk-shaped atom with negatively charged particles orbiting a positive nucleus.
83
What shape did Nagaoka's atomic model describe?
Disk-shaped
## Footnote
This model depicted negatively charged particles orbiting a positively charged nucleus.
84
What did Rutherford note about his results regarding Nagaoka's model?
They would be the same if Nagaoka's model were correct
## Footnote
This indicates the compatibility of their models despite different descriptions.
85
What large region do atoms possess according to Rutherford's theory?
A mostly empty space
## Footnote
This empty space is where electrons are thought to exist around the nucleus.
86
Fill in the blank: The _______ in the gold foil experiment were deflected off course.
Some alpha particles
## Footnote
This phenomenon indicated that certain alpha particles interacted with the dense positive center.
87
What is the central region of an atom called?
Nucleus
## Footnote
The nucleus is positively charged and contains almost all of the atom's mass.
88
What particles are located in the outer region of the atom?
Electrons
## Footnote
Electrons have a single negative charge and are much less massive than protons and neutrons.
89
Who proposed the 'solar-system' atomic model in 1911?
Ernest Rutherford
## Footnote
Rutherford's model visualized electrons moving around the nucleus similar to planets orbiting the Sun.
90
What is a proton?
A positively charged particle in the nucleus
## Footnote
A proton has about the same mass as 1836 electrons.
91
What is the term for atoms of the same element that differ in mass but are chemically alike?
Isotopes
## Footnote
Isotopes have the same number of protons but different numbers of neutrons.
92
What did Harriet Brooks discover about thorium?
It emits radioactive emissions that are actually a simpler atom, radon
## Footnote
Brooks was the first to recognize that one element could transmute into another.
93
What did Rutherford hypothesize about helium atoms?
They contain two protons and two neutrons
## Footnote
This would make helium four times as massive as hydrogen, which has one proton and one electron.
94
What is the volume of space surrounding the nucleus called?
Empty space
## Footnote
This space is large compared to the nucleus and contains the electrons.
95
True or False: Rutherford's model suggested that atoms are packed closely together.
True
## Footnote
Rutherford assumed that atoms in the gold foil were closely packed, allowing most alpha particles to pass through.
96
Fill in the blank: The particle hypothesized by Rutherford that has no electrical charge is called a _______.
Neutron
## Footnote
The neutron is hypothesized to have the same mass as the proton.
97
What is the mass relationship between hydrogen and helium atoms according to Rutherford's hypothesis?
Helium atoms are four times more massive than hydrogen atoms
## Footnote
This was explained by the presence of neutrons in helium.
98
What is the significance of Rutherford's reasoning about the nucleus?
It showed that the nucleus is extremely small and dense
## Footnote
This contradicts Thomson's idea of a cloud of positive charge.
99
What is the isotope of neon with 10 neutrons called?
neon-10
100
What is the isotope of neon with 12 neutrons called?
neon-12
101
How many protons do all neon atoms have?
10
102
What particle has no electric charge and was difficult to isolate?
neutron
103
Who provided experimental evidence for the existence of neutrons?
James Chadwick
104
What major objection was raised against Rutherford's atomic model?
Electrons should emit energy and spiral into the nucleus
105
What is emitted by gases in a discharge tube when electrical energy is supplied?
light
106
What does the spectrum of light correspond to?
specific wavelengths
107
Who hypothesized that electrons have allowed energy levels?
Niels Bohr
108
What are the specific energy levels associated with electrons called?
electron shells
109
True or False: Electrons can exist between energy levels.
False
110
What happens when an electron absorbs energy?
It moves to a higher energy level
111
What happens when an electron emits energy?
It moves back to its original energy level
112
What shape do the energy levels of electrons have in three dimensions?
spherical shells
113
What are alpha particles now known to be?
helium nuclei
114
How many protons and neutrons are in an alpha particle?
2 protons and 2 neutrons
115
What was Niels Bohr a leading advocate for in later life?
international cooperation in peaceful uses of atomic energy
116
Stopped on page 20
117
What year did Bohr propose his atomic theory?
1913
118
What do electrons in atoms of different elements have?
Different allowed energy levels
119
What does the hydrogen spectrum represent?
Light with certain energy
120
How did Bohr describe the movement of electrons in the hydrogen atom?
In circular paths
121
What happens to an electron when it absorbs energy?
It moves further from the positively charged nucleus
122
What did Bohr calculate regarding electrons in a hydrogen atom?
Average distance from the nucleus
123
Can Bohr's equations be applied to atoms with more than one electron?
No, they were too complex
124
What is the maximum number of electrons in the first two energy levels?
Varies by energy level
125
What is a neutrino?
A subatomic particle produced in great numbers by the Sun
126
Where do Canadian researchers study neutrinos?
Sudbury Neutrino Observatory
127
True or False: Electrons in the same energy level are now thought to be grouped in pairs.
True
128
What are neutrons and protons believed to be made of?
Even smaller particles
129
Fill in the blank: Electrons can only exist at certain _______.
Energy levels
130
What feature of Bohr's theory is key to understanding electron behavior?
Energy levels of electrons
131
What mathematical aspect did Bohr derive for the hydrogen atom?
Equations describing energy levels
132
What is the significance of the characteristic arrangement of electrons in each element?
Determines the element's properties
133
What type of model did Rutherford propose?
Nuclear model of the atom
134
Fill in the blank: Bohr's theory fit well with observations of light emitted from _______.
Discharge tubes
135
136
What is the basic structure of an atom?
An atom consists of a nucleus containing protons and neutrons, with electrons occupying the surrounding space.
## Footnote
Protons and neutrons are collectively known as nucleons.
137
What are the charges of protons, neutrons, and electrons?
Protons: 1+
Neutrons: 0
Electrons: 1-
## Footnote
Protons have a positive charge, neutrons have no charge, and electrons have a negative charge.
138
What is the average diameter of an atom?
Approximately 10^-10 m.
## Footnote
This size is difficult to visualize; if an atom were the size of a grain of sand, a strand of hair would be about 60 m in diameter.
139
What is the nucleus of an atom?
The central core of an atom, composed of protons and neutrons.
## Footnote
The nucleus is where the majority of an atom's mass is concentrated.
140
What are isotopes?
Atoms of the same element that have the same number of protons but differing numbers of neutrons.
## Footnote
Isotopes have the same atomic number but different mass numbers.
141
What is an atomic number?
The number of protons in the nucleus of an atom, which identifies the element.
## Footnote
The atomic number is unique to each element.
142
What is a mass number?
The total number of protons and neutrons in an atom's nucleus.
## Footnote
The mass number helps to identify specific isotopes.
143
How is the composition of an atom typically represented?
Using the atomic number and mass number.
## Footnote
These two numbers help identify a particular isotope of an element.
144
What is the relative charge of a neutron?
0.
## Footnote
Neutrons are electrically neutral particles.
145
Fill in the blank: Protons and neutrons are collectively known as _______.
nucleons.
146
True or False: Electrons exist in a fixed position around the nucleus.
False.
## Footnote
Electrons exist in a fuzzy, cloud-like region around the nucleus at certain allowed energy levels.
147
What is the symbol for hydrogen-1?
H.
## Footnote
Hydrogen-1 is the most common isotope of hydrogen.
148
What is the mass of a proton?
Approximately 1.67 x 10^-24 g.
## Footnote
This is a typical mass for protons and is similar for neutrons.
149
What is the difference between hydrogen-2 and hydrogen-3?
Hydrogen-2 is known as deuterium, and hydrogen-3 is known as tritium.
## Footnote
Both are isotopes of hydrogen with differing numbers of neutrons.
150
How do you determine the number of neutrons in a nucleus?
By subtracting the atomic number from the mass number.
151
What is the mass number of lithium-7?
7
152
What is the atomic number of lithium?
3
153
How many neutrons are in lithium-7?
4
154
What must be true about the number of electrons in a neutral atom?
It must equal the number of protons.
155
What is the relationship between atomic number and electrons in a neutral atom?
The atomic number is the same as the number of electrons.
156
State the number of neutrons in the isotope 6Ne.
4
157
State the number of neutrons in the isotope $He.
1
158
State the number of neutrons in the isotope 8Ca.
4
159
State the number of neutrons in the isotope AI.
7
160
How many protons are in Oxygen-17?
8
161
How many electrons are in Oxygen-17?
8
162
How many neutrons are in Oxygen-17?
9
163
If an isotope has a mass number of 35 and 18 neutrons, what is its atomic number?
17
164
What is the atomic symbol of an isotope with mass number 35 and atomic number 17?
Cl
165
Use nuclear notation to represent an isotope with mass number 35 and atomic number 17.
^{35}_{17}Cl
166
How many neutrons are in sodium-23?
12
167
What was examined in Section 1.2?
Evidence that led to an atomic theory involving protons and neutrons in a nucleus surrounded by electrons.
168
What does the arrangement of electrons affect?
How compounds form.
