S1CH1 Flashcards
1
Q
what is the formula of formic acid?
A
CH2O2
2
Q
what is CH2O2?
A
formic acid
3
Q
what determines the properties of a compound such as formic acid?
A
1) A compound is made of atoms joined by bonds. Formic acid (CH2 O2 )
consists of carbon (C), hydrogen (H), and oxygen (O).
2) The number of protons ( + ) determines an atom’s identity. Oxygen has 8 protons.
3) An atom’s electron ( – ) distribution determines its ability to form bonds.
Oxygen has space for 2 more electrons, so it can form 2 bonds.
4) A compound’s properties depend on its atoms and how they are bonded together. In formic acid, this O attracts H’s electron, releasing H+ and making this compound an acid, which stings.
4
Q
what does formic acid consist of?
A
carbon (C), Hydrogen (H) and Oxygen (O)
5
Q
how many protons does oxygen have?
A
8.
6
Q
how many space does oxygen have?
A
it has space for 2 more electrons so it can form 2 bonds.
7
Q
how many bonds can oxygen form?
A
2
8
Q
how are the atoms in formic acid bonded together
A
In formic acid, O attracts H’s electron, releasing H+ and making this compound an acid, which stings.
9
Q
what is a property of formic acid?
A
it stings
10
Q
what animals use chemistry to ward off enemies?
A
wood ants (formica rufa)
11
Q
how do wood ants (formica rufa ward off enemies using chemistry?
A
When threatened from above, they shoot volleys of formic acid from their abdomens into the air. The acid bombards and stings potential predators, such as hungry birds.
12
Q
what does matter consist of?
A
Matter consists of chemical elements in pure form and in combinations called compounds
13
Q
what are organisms composed of?
A
matter
14
Q
what is matter?
A
anything that takes up space and has mass. Matter exists in many forms.
15
Q
what is matter made up of?
A
elements
16
Q
what is an element?
A
An element is a substance that cannot be broken down to other substances by chemical reactions.
17
Q
how many elements did chemists recognize occurring in nature
A
92.
18
Q
each element has what?
A
Each element has a symbol, usually the first letter or two of its name. Some symbols are derived from Latin or German
19
Q
what is the symbol for sodium and where does it come from?
A
the symbol for sodium is Na, from the Latin word natrium.
20
Q
what is a compound?
A
A compound is a substance consisting of two or more different elements combined in a fixed ratio.
21
Q
example of compound?
A
Table salt, for example, is sodium chloride (NaCl), a compound composed of the elements sodium (Na) and chlorine (Cl) in a 1:1 ratio. Pure sodium is a metal, and pure chlorine is a poisonous gas. When chemically combined, however, sodium and chlorine form an edible compound.
22
Q
what is example of 2:1 ratio?
A
Water (H 2O), another compound, consists of the elements hydrogen (H) and oxygen (O) in a 2:1 ratio
23
Q
what are examples of emergent properties? and what does it mean?
A
NaCl and H2O. it means A compound has characteristics different from those of its elements
24
Q
Of the 92 natural elements, about 20–25% are what?
A
essential properties
25
Of the 92 natural elements, about how many are essential properties
20-25%
26
what are essential elements?
Of the 92 natural elements, about 20–25% are essential elements that an organism needs to live a healthy life and reproduce. The essential elements are similar among organisms, but there is some variation—for example, humans need 25 elements, but plants need only 17.
27
is essential elements same among organisms?
No there are different variations but they are similar
28
the emergent property of NaCl?
The metal sodium combines with the poisonous gas chlorine, forming the edible compound sodium chloride, or table salt.
29
what are the 4 elements that make up approximately 96% of living matter?
Just four elements—oxygen (O), carbon (C), hydrogen (H), and nitrogen (N)—make up approximately 96% of living matter.
30
how much do oxygen, hydrogen, carbon and nitrogen make up in living matter?
96%
31
what elements account for the remaining 4% or so?
Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), and a few other elements account for most of the remaining 4% or so of an organism’s mass
32
Calcium (Ca), phosphorus (P), potassium (K), sulfur (S), make up how much of the body mass of a living thing?
4% or so
33
what is trace elements?
Trace elements are required by an organism in only minute quantities.
34
Some trace elements, such as what, are needed by all forms of life;
iron (fe)
35
what is an example of element required by only certain species
in vertebrates (animals with backbones), the element iodine (I) is an essential ingredient of a hormone produced by the thyroid gland. A daily intake of only 0.15 milligram (mg) of iodine is adequate for normal activity of the human thyroid
36
in what animals ), the element iodine (I) is an essential ingredient of a hormone produced by the thyroid gland. A daily intake of only 0.15 milligram (mg) of iodine is adequate for normal activity of the human thyroid
vertebrates (animals with backbones)
37
n vertebrates (animals with backbones), which element is an essential ingredient of a hormone produced by the thyroid gland
iodine (I)
38
in vertebrates (animals with backbones), the element iodine (I) is an essential ingredient of what?
essential ingredient of a hormone produced by the thyroid gland
39
n vertebrates (animals with backbones), the element iodine (I) is an essential ingredient of a hormone produced by which gland.
thyroid gland
40
A daily intake of only how much of iodine is adequate for normal activity of the human thyroid
0.15 milligrams (mg)
41
A daily intake of only 0.15 milligram (mg) of what is adequate for normal activity of the human thyroid
iodine
42
. A daily intake of only 0.15 milligram (mg) of iodine is adequate for normal activity of what
human thyroid
43
An what deficiency in the diet causes the thyroid gland to grow to abnormal size,
iodine deficiency
44
An iodine deficiency in the diet causes what gland to grow to abnormal size,
the thyroid gland
45
An iodine deficiency in the diet causes the thyroid gland to grow to abnormal size, what is this condition called?
goiter
46
what is goiter?
An iodine deficiency in the diet causes the thyroid gland to grow to abnormal size, this is called goiter
47
Consuming seafood or iodized salt reduces the incidence of what conditions .
goiter
48
Consuming what reduces the incidence of goiter.
seafood or iodized salt
49
Some naturally occurring elements are toxic to organisms for example?
In humans, for instance, the element arsenic has been linked to numerous diseases and can be lethal. In some areas of the world, arsenic occurs naturally and can make its way into the groundwater. As a result of using water from drilled wells in southern Asia, millions of people have been inadvertently exposed to arsenic-laden water
50
the element arsenic has been linked to numerous diseases and can be lethal. In some areas of the world, arsenic occurs naturally and can make its way into the groundwater. As a result of using water from drilled wells in where?, millions of people have been inadvertently exposed to arsenic-laden water
southern asia
51
In humans, for instance, the element arsenic has been linked to numerous diseases and can be lethal. In some areas of the world, arsenic occurs naturally and can make its way into the where?.
groundwater
52
are all naturally occurring elements safe?
No, Some naturally occurring elements are toxic to organisms
53
Percentage of Body Mass (including water) of Oxygen
65.0%
54
Percentage of Body Mass (including water) of carbon
18.5%
55
Percentage of Body Mass (including water) of hydrogen
9.5%
56
Percentage of Body Mass (including water) of Nitrigen
3.3%
57
Percentage of Body Mass (including water) of Calcium
1.5%
58
Percentage of Body Mass (including water) of phosphorus
1%
59
Percentage of Body Mass (including water) of potassium
0.4%
60
Percentage of Body Mass (including water) of Sulfur
0.3%
61
Percentage of Body Mass (including water) of sodium
0.2%
62
Percentage of Body Mass (including water) of chlorine
0.2%
63
Percentage of Body Mass (including water) of magnesium
0.1%
64
what makes 96.3%Percentage of Body Mass (including water) of
oxygen, hydrogen, nitrogen, carbon
65
what makes 3.7% Percentage of Body Mass (including water) of
Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium
66
Trace elements (less than 0.01% of mass): are which?
Boron (B), chromium (Cr) cobalt (Co), copper (Cu), fluorine (F), iodine (I), iron (Fe), manganese (Mn), molybdenum (Mo), selenium (Se), silicon (Si), tin (Sn), vanadium (V), zinc (Zn)
67
Some species have become adapted to environments containing elements that are usually toxic; what is an example?
an example is serpentine plant communities. Serpentine is a jade-like mineral that contains elevated concentrations of elements such as chromium, nickel, and cobalt. Although most plants cannot survive in soil that forms from serpentine rock, a small number of plant species have adaptations that allow them to do so Presumably, variants of ancestral, nonserpentine species arose that could survive in serpentine soils, and subsequent natural selection resulted in the distinctive array of species we see in these areas today.
68
what is serpentine?
Serpentine is a jade-like mineral that contains elevated concentrations of elements such as chromium, nickel, and cobalt.
69
Serpentine is a jade-like mineral that contains elevated concentrations of elements such as what?.
chromium, cobalt nickel
70
what is serpentine plant community
Serpentine plant community. These plants are growing on serpentine soil, which contains elements that are usually toxic to plants. The insets show a close-up of serpentine rock and one of the plants, a Tiburon Mariposa lily (Calochortus tiburonensis). This specially adapted species is found only on this one hill in Tiburon, a peninsula that juts into San Francisco Bay.
71
Serpentine plant community. These plants are growing on serpentine soil, which contains elements that are usually toxic to plants. The insets show a close-up of serpentine rock and one of the plants, whats its name? This specially adapted species is found only on this one hill in Tiburon, a peninsula that juts into San Francisco Bay.
tiburon maripose lily (calochortus tiburonesis)
72
Serpentine plant community. These plants are growing on serpentine soil, which contains elements that are usually toxic to plants. The insets show a close-up of serpentine rock and one of the plants, a Tiburon Mariposa lily (Calochortus tiburonensis). This specially adapted species is found only on where?
This specially adapted species is found only on this one hill in Tiburon, a peninsula that juts into San Francisco Bay.
73
Explain how table salt has emergent properties.
The emergent properties of a compound. The metal sodium combines with the poisonous gas chlorine, forming the edible compound sodium chloride, or table salt.
74
Is a trace element an essential element? Explain.
yes, some trace elements can be essential but they are required in minute quantities.
75
In humans, iron is a trace element required for the proper functioning of hemoglobin, the molecule that carries oxygen in red blood cells. What might be the effects of an iron deficiency?
hemoglobin may function improperly and cause less oxygens to be carried in red blood cells which decreases blood.
76
Explain how natural selection might have played a role in the evolution of species that are tolerant of serpentine soils.
because serpentine is usually toxic to plants these species have adapted to the environment in order to survive. Presumably, variants of ancestral, nonserpentine species arose that could survive in serpentine soils, and subsequent natural selection resulted in the distinctive array of species we see in these areas today
77
an element’s properties depend on what?
the structure of its atoms
78
what depends on the structure of its atoms?
an elements properties
79
each element contains what?
Each element consists of a certain type of atom that is different from the atoms of any other element.
80
what is an atom?
An atom is the smallest unit of matter that still retains the properties of an element.
81
what is the smallest unit of matter that still retains the properties of an element.
an atom
82
what do we symbolize atoms with?
we symbolize atoms with the same abbreviation used for the element that is made up of those atoms. For example, the symbol C stands for both the element carbon and a single carbon atom.
83
what is the smallest unit having the properties of an element,
an atom
84
what is an atom composed of?
even smaller parts called subatomic particles
85
Using what, physicists have produced more than 100 types of particles from the atom,
high energy collisions
86
how many essential elements do humans need?
25
87
how many essential elements do plants need?
17
88
Using high-energy collisions, physicists have produced how many types of particles from the atom,
more than 100 types.
89
what are the 3 subatomic particles
proton neutron electrons
90
which subatomic particles are electrically charged
protons and electrons
91
which subatomic particle is neutral
neutron
92
what are the charges of proton and electrons
Each proton has one unit of positive charge, and each electron has one unit of negative charge.
93
which subatomic particles are packed together tightly in a dense core or atomic nucleus
protons and neutrons
94
Protons and neutrons are packed together tightly in a dense core, called what
atomic nucleus
95
where is aromic nucleus
at the center of an atom
96
what is the charge of nucleus
positive because of protons
97
what gives nucleus its positive charge?
protons
98
The rapidly moving electrons form a “what around the nucleus
cloud of negative charge
99
The rapidly moving what form a “cloud” of negative charge around the nucleus
electrons
100
The rapidly moving electrons form a “cloud” of negative charge around the where?
nucleus
101
it is what that keeps the electrons in the vicinity of the nucleus
attraction between opposite charges
102
it is the attraction between opposite charges that keeps the what in the vicinity of the nucleus
electrons
103
it is the attraction between opposite charges that keeps the electrons in the vicinity of the what
nucleus
104
helium (He) atom. The helium nucleus consists of how many protons, neutrons and electrons?
2 of each
105
which subatomic particle are almost identical in mass,
protons and neutrons
106
The neutron and proton are almost identical in mass, what is their mass
1.7 x 10-24 gram
107
what units are not very useful for describing the mass of objects that are so minuscule.
grams and other conventional units
108
for measuring mass of atoms and subatomic particles (and for molecules, too), we use a unit of measurement called what
the dalton
109
for measuring the mass of what, we use a unit of measurement called the dalton
atoms and subatomic particles (and for molecules, too)
110
what is the unit the dalton named after?
in honor of John Dalton, the British scientist who helped develop atomic theory around 1800
111
who is john dalton?
the British scientist who helped develop atomic theory around 1800
112
who was the British scientist who helped develop atomic theory around 1800
john dalton
113
John Dalton, the British scientist who helped develop what around what time
atomic theory around 1800
114
what is the same as the atomic mass unit, or amu,
the dalton
115
The dalton is the same as what
the atomic mass unit, or amu
116
whic subatomic particle have masses close to 1 dalton.
protons and neutrons
117
Neutrons and protons have masses close to how many dalton.
1
118
most of the mass of an atom is occupied by which subatomic particles
proton and neutrons
119
the mass of an electron is only about how much that of a neutron or proton
1/2000
120
the mass of what is only about 1/2,000 that of a neutron or proton
an electron
121
the mass of an electron is only about 1/2,000 that of what
a neutron or proton
122
what is ignored when computing the total mass lf an atom?
electrons mass
123
Atoms of the various elements differ in their number of subatomic particles. true or false
true
124
Atoms of the various elements dont differ in their number of subatomic particles. true or false
false they differ
125
Atoms of the various elements differ in their what
number of subatomic particles
126
what differ in their number of subatomic particles.
atoms of various elements
127
Atoms of the same or various elements differ in their number of subatomic particles.
various
128
alll atoms of a particular element have the same number of protons in their nuclei. true or false
true
129
alll atoms of a particular element have the different number of protons in their nuclei true or false
false they have the same number
130
alll atoms of a particular element have the same number of what in their nuclei
protons
131
alll atoms of a particular element have the same number of protons in their where
nuclei
132
alll atoms of a same or different element have the same number of protons in their nuclei
same
133
number of what is unique to that element
protons
134
This number of protons, which is unique to that element, is called the what
atomic number
135
how is atomic number written
the atomic number and is written as a subscript to the left of the symbol for the element.
136
the atomic number and is written as a what to the left of the symbol for the element.
subscript
137
the atomic number and is written as a subscript to the where of the symbol for the element.
left
138
the atomic number and is written as a subscript to the left of the what for the element.
symbol
139
. The abbreviation2 He, for example, tells us what
that an atom of the element helium has 2 protons in its nucleus.
140
an atom is neutral in what, which means that its protons must be balanced by an equal number of electrons.
electrical charge
141
an atom is neutral in electrical charge, which means that its what must be balanced by an equal number of electrons.
protons
142
an atom is neutral in electrical charge, which means that its protons must be balanced by an equal number of what.
electrons
143
in an atom of different elements, number of protons = number of electrons. true or false?
false, must be same element
144
in an atom of same elements, number of protons = number of electrons. true or false?
true
145
the atomic number tells us what in an electrically neutral atom.
the number of protons and also numbers of electrons
146
the atomic number tells us the number of protons and also the number of electrons in an what type atom.
electrically neutral
147
we find the number of neutrons by what quantity
mass number
148
what kind we find using mass number
neutrons number
149
what is the-mass number
the mass number, which is the total number of protons and neutrons in the nucleus of an atom
150
the mass number, which is the total number of what in the nucleus of an atom
protons and neutrons
151
how is the mass number written
The mass number is written as a superscript to the left of an element’s symbol.
152
The mass number is written as a what to the left of an element’s symbol.
superscript
153
The mass number is written as a superscript to the where of an element’s symbol.
left
154
The mass number is written as a superscript to the left of an element’s what.
symbol
155
For example, we can use this shorthand to write an atom of helium as2 4 He. this indicates what
Because the atomic number indicates how many protons there are, we can determine the number of neutrons by subtracting the atomic number from the mass number. In our example, the helium atom2 4 He has 2 neutrons.
156
Because the atomic number indicates how many protons there are, we can determine the number of neutrons by subtracting what from the mass number.
atomic number
157
Because the atomic number indicates how many protons there are, we can determine the number of neutrons by doing what?
subtracting the atomic number from the mass number.
158
subtracting the atomic number from the mass number. gives us what
number of neutrons
159
23 11 Na what is mass number, atomic number, electron proton and neutron number for sodium
mass number =23
atomic number= 11
proton =11
electron =11
neutron = 12
160
The simplest atom is what
hydrogen 1-1
161
why is The simplest atom is hydrogen1 1 H,
because it has no neutrons; it consists of a single proton with a single electron.
162
the contribution of what to mass is negligible, almost all of an atom’s mass is concentrated in its nucleus.
electrons
163
the contribution of electrons to mass is negligible, almost all of an atom’s mass is concentrated in its where.
nucleus
164
protons and neutrons uave a mass close to what, so the mass number is close to, but slightly different from, the total mass of an atom,
1 dalton
165
protons and neutrons uave a mass close to 1 daltin, so the what is close to, but slightly different from, the total mass of an atom,
mass number
166
protons and neutrons uave a mass close to what, so the mass number is close to, but slightly different from, what
the totak mass of the atom
167
what sthe total mass of an atom called
atomic mass
168
what is atomic mass
total mass of an atom
169
the mass number of sodium (2311Na) is 23, but its atomic mass is 22.9898 daltons; whis explqins what?
this explains the difference between mass number and atomic mass
170
All atoms of a given element have the same number of what,
protons
171
All atoms of a given element have the same number of protons, but some atoms have more what than other atoms of the same element and therefore have greater mass.
neutrons
172
All atoms of a given element have the same number of protons, but some atoms have more neutrons than other atoms of the same element and therefore have greater what.
mass
173
All atoms of a given element have the same number of protons, but some atoms have more neutrons than other atoms of the same element and therefore have greater mass. These different atomic forms of the same element are called what of the element
isotopes
174
what is isotopes
All atoms of a given element have the same number of protons, but some atoms have more neutrons than other atoms of the same element and therefore have greater mass. These different atomic forms of the same element are called isotopes of the element
175
In nature, can an element occur as a mixture of its isotopes.?
yes, In nature, an element may occur as a mixture of its isotopes. As an example, the element carbon, which has the atomic number 6, has three naturally occurring isotopes.
176
, the element carbon, which has the atomic number of what, has three naturally occurring isotopes.
6
177
In nature, an element may occur as a mixture of its isotopes. As an example, the element carbon, which has the atomic number 6, has how many naturally occurring isotopes.
3
178
The most common isotope of carbon is what, which accounts for about 99% of the carbon in nature
Carbon 12 or 12 6 C
179
The most common isotope is carbon-12,612C, which accounts for about how many percent % of the carbon in nature
99%
180
The most common isotope is carbon-12,612C, which accounts for about 99% of the carbon in nature how many neutrons does it have
6
181
Most of the remaining what percent % of carbon consists of atoms of the isotope613C, with 7 neutrons
1%
182
Most of the remaining 1% of carbon consists of atoms of the what isotopes ,
Carbon-13 13 6 C
183
Most of the remaining 1% of carbon consists of atoms of the isotope613C, with how many neutrons
7
184
A third, even rarer isotope of carbon ,is what ,
carbon 14, 14 6 C
185
A third, even rarer isotope,614C, has how many neutrons.
8
186
all three isotopes of carbon have how many what; otherwise, they would not be carbon.
6 protons
187
the isotopes of an element have slightly different what
masses
188
Although the isotopes of an element have slightly different masses, how they behave in chemical reactions.
identically
189
an element with more than one naturally occurring isotope, the atomic mass is an what?.
average of those isotopes, weighted by their abundance
190
, carbon has an atomic mass of how many daltons.)
12.01
191
Both12 C and13 C are what isotopes, meaning that their nuclei do not have a tendency to lose subatomic particles, a process called decay
stable
192
what carbon isotopes are stable isotopes, meaning that their nuclei do not have a tendency to lose subatomic particles, a process called decay
12 C and 13C
193
Both12 C and13 C are stable isotopes, meaning what
that their nuclei do not have a tendency to lose subatomic particles, a process called decay
194
stable isotopes that their nuclei do not have a tendency to lose subatomic particles, a process called what
decay
195
The isotope what, however, is unstable, or radioactive
14 C
196
The isotope14C, however, is what
unstable or radioactive
197
A what is one in which the nucleus decays spontaneously, giving off particles and energy.
radioactive isotopes
198
what are radioactive isotopes
A radioactive isotope is one in which the nucleus decays spontaneously, giving off particles and energy.
199
A radioactive isotope is one in which the nucleus decays spontaneously, giving off what 2 things
particles and energy
200
the radioactive decay leads to a change in the number of protons, it transforms the atom to an atom of a different element. true or false?
true
201
the radioactive decay leads to a change in the number of what, it transforms the atom to an atom of a different element.
protons
202
when a carbon-14 (14C) atom decays, a what decays into a proton, transforming the atom into a nitrogen (14N) atom.
neutron
203
when a carbon-14 (14C) atom decays, a neutron decays into a what, transforming the atom into a nitrogen (14N) atom.
proton
204
when a carbon-14 (14C) atom decays, a neutron decays into a proton, transforming the atom into a what atom.
nitrogen (14N)
205
Radioactive isotopes have many useful applications in what.
biology
206
what have many useful applications in biology.
radioactive isotopes
207
what are often used as diagnostic tools in medicine.
radioactive isotopes
208
what can use radioactive atoms just as they would use nonradioactive isotopes of the same element
cells
209
The radioactive isotopes are incorporated into biologically active molecules, which are then used as what to track atoms during metabolism, the chemical processes of an organism.
tracers
210
tracers do what
The radioactive isotopes are incorporated into biologically active molecules, which are then used as tracers to track atoms during metabolism, the chemical processes of an organism.
211
whats metabolism
the chemical processes of an organism.
212
certain what disorders are diagnosed by injecting small doses of radioactively labeled substances into the blood and then analyzing the tracer molecules excreted in the urine.
kidney
213
certain kidney disorders are diagnosed by injecting small doses of radioactively labeled substances into the where and then analyzing the tracer molecules excreted in the urine.
blood
214
certain kidney disorders are diagnosed by injecting small doses of radioactively labeled substances into the blood and then analyzing the tracer molecules excreted in the where.
urine
215
Radioactive tracers are also used in combination with sophisticated imaging instruments, such as PET scanners that can what?
monitor growth and metabolism of cancers in the body.
216
Radioactive tracers are also used in combination with sophisticated imaging instruments, such as what
PET scanners
217
Radioactive tracers are also used in combination with sophisticated what instruments, such as PET scanners
imaging
218
what are also used in combination with sophisticated imaging instruments, such as PET scanners that
radioactive tracers
219
PET, an acronym for what
PET, an acronym for positronemission tomography,
220
PET, an acronym for positronemission tomography, detects what
PET, an acronym for positronemission tomography, detects locations of intense chemical activity in the body. The bright yellow spot marks an area with an elevated level of radioactively labeled glucose, which in turn indicates high metabolic activity, a hallmark of cancerous tissue.
221
PET, an acronym for positronemission tomography, detects locations of intense chemical activity in the body. The bright yellow spot marks an area with an elevated level of what, which in turn indicates high metabolic activity, a hallmark of cancerous tissue.
radiactively labeled glucose
222
PET, an acronym for positronemission tomography, detects locations of intense chemical activity in the body. The bright yellow spot marks an area with an elevated level of radioactively labeled glucose, which in turn indicates what which shows what
high metabolic activity, a hallmark of cancerous tissue.
223
radioactive isotopes are very useful in what and what,
biological research and medicine
224
radioactive isotopes are very useful in biological research and medicine, radiation from decaying isotopes also poses a hazard to life by damaging what
cellular molecules
225
radioactive isotopes are very useful in biological research and medicine, radiation from decaying isotopes also poses a hazard to life by damaging cellular molecules the severity depends on what!
The severity of this damage depends on the type and amount of radiation an organism absorbs.
226
The severity of this damage depends on the type and amount of radiation an organism absorbs. what is an example?
One of the most serious environmental threats is radioactive fallout from nuclear accidents.
227
The doses of most isotopes used in medical diagnosis, however, are what.
safe
