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Atomic Mass
Atomic mass is the mass of protons, neutrons, and electrons in a single specific atom.
1,752 Questions
What is the atomic mass of Pb?
The atomic mass of lead (Pb) is approximately 207.2 atomic mass units.
Why is atomic mass not a constant number?
The atomic mass is the average of all of the different isotopes of the element present in the sample. Samles taken from aound the worlld for some elements have slightly different isotope ratios and therefore have different atomic masses.
Is periodicity defined as the fact that elements increase in atomic mass in a regular way?
No, the periodicity of the Periodic Table of Elements refers to the fact that the chemical properties of elements vary in a periodic way, from metals on the left hand side of the table to non-metals and then to noble gases in the far right hand column. Each row goes through the same variations. There is nothing periodic about the increase in mass; that would be described as a linear progression rather than a periodic phenomenon.
What is atomic mass of an atom?
The atomic mass of an atom is the sum of the number of protons and neutrons in the nucleus. It is generally expressed in atomic mass units (amu). The atomic mass is important for determining the overall mass of an atom and for calculating molar masses in chemical reactions.
Phosphorus has an atomic mass of 31 and an atomic number of 15 the number of neutrons must be?
Mass number = no. of protons + neutrons Atomic number = no. of protons
Thus (mass number - atomic number) gives you no. of neutrons.
Therefore for phosphorus, the number of neutrons would be 16.
Given : Atomic mass of B = 10.01 amu , % = 19.9 let it be A Atomic mass of B = 11.01 amu , % = 80.1 Solution : A and B are approximately in the ratio 1:4. Isotopic mass = [(proportion of A X at. mass of A) + (proportion of B X at. mass of B)] / 4 = [(1 X 10.01) + (4 X 11.01)] / 4 = (10.01 + 44.04) / 4 = 54.05 / 4 Isotopic atomic mass = 13.512 amu ---- Therefore, isotopic atomic mass of B is = 13.512 amu.
Are Mass and atomic mass the same?
Mass would denote, in layman's terms, the total amount of matter something has. For example, we humans have mass, and weight (an oft confused but totally different thing) is the pressure it takes to keep us on the ground. Atomic mass however, refers to the overall mass of an atom. This value is measured in amu (atomic mass units). Approximately, each proton and neutron is worth 1 amu, while the weight of electrons is almost so small that it has little effect in small amounts.
What is an example of an Atomic Mass?
An example of an atomic mass is the value associated with an atom of carbon-12, which is exactly 12 atomic mass units. This value represents the average mass of the protons, neutrons, and electrons in a carbon-12 atom.
Why is atomic mass for an element an average on the periodic table?
The atomic mass is an average because most atoms have isotopes sometimes up to 10 or more. These all have different numbers of neutrons and subsiquently different weights. For this reason an average of these weights needs to be used for the atomic mass.
What does the average atomic mass represent?
The average Atomic Mass represents the weighted average of the masses of the isotopes of the element.
To calculate the average atomic mass, multiply the mass of each isotope by its natural abundance (expressed as a decimal), then add the results together. For the unknown element: Average atomic mass = (0.7547 * 248.7 amu) + (0.2453 * x) Given the only known isotope mass is 248.7 amu, you'll have to provide the mass of the second isotope to determine the average atomic mass.
Who invented the atomic mass unit?
The concept of the atomic mass unit was established by chemist John Dalton in the early 1800s. Dalton introduced the idea of using a standard unit to represent the mass of atoms relative to each other.
Mass weigthed average and area weighted avg?
The mass-weighted average accounts for the influence of each sample's mass on the overall average, giving greater weight to samples with higher mass. The area-weighted average, on the other hand, considers the influence of each sample's area or size on the overall average, giving greater weight to samples with larger surface area. Both methods provide a way to calculate a representative value that reflects the contribution of each individual sample.
Approximately 78 grams The mole as a unit lets us recycle the number found in the average atomic mass and place a new much larger and therefore easier to work with unit. This unit is the gram. So in this case 1 average atom of K has a mass of 39 amu and 1 mole of atoms of K have a mass of 39 grams. So since you want 2.0 mol of K you just have to multiply the atomic mass found on the periodic table by 2.0
Is there an atom with an atomic mass of 200?
Yes. There's even a stable atom with an atomic mass of 200 (well, not QUITE 200): Mercury has a stable isotope with a mass of 199.9683. Several other elements (platinum, gold, lead, etc.) have isotopes with atomic mass near 200, but they're all radioactive.
Kripton is a metal element. Atomic mass of it is 83.80.
Atomic mass unit is equal to what?
Unified atomic mass unit, a small unit of mass used to express atomic and molecular masses.
The atomic mass unit is equal to one-twelfth the mass of a carbon-12 atom or 1,660538921(73)×10−27 kg.
Where is the atomic mass in the periodic table of elements?
On the periodic table each element will have 2 numbers. One will be a whole number going from 1 hydrogen to 113 or so. This is the atomic number which is the number of protons it has. There will also be a number with a few decimal places. Carbon has a atomic number of 6 (as it is element number 6 and has 6 protons.) and an atomic mass of 12.011. The atomic mass is the average mass of a an atom for Carbon 99% of the atoms have a mass 12 (6 protons and 6 neutrons) and 1% has a mass of 13 the average of the two (0.99 X 12) + (0.01 X 13) = 12.011
How do you find the atomic mass of lithium?
The atomic mass of lithium is found by adding the mass of its protons and neutrons in its nucleus. It is calculated by taking the weighted average of the isotopes of lithium found in nature, where lithium-6 and lithium-7 are the most abundant isotopes. The atomic mass of lithium is approximately 6.94 atomic mass units.
What is a proton weighs atomic mass units?
A proton's mass is approximately 1 atomic mass unit, roughly 1.6726 x 10^-27 kilograms.
All elements with their atomic numbers and atomic mass?
Click a column title, such as Symbol, to sort the table by that item.
Electron
configuration
1　
1.0079
Hydrogen
H
-259
-253
0.09
0.14
1776
1
1s1
13.5984
2　
4.0026
Helium
He
-272
-269
0.18　
1895
18
1s2
24.5874
3　
6.941
Lithium
Li
180
1347
0.53　
1817
1
[He] 2s1
5.3917
4　
9.0122
Beryllium
Be
1278
2970
1.85　
1797
2
[He] 2s2
9.3227
5　
10.811
Boron
B
2300
2550
2.34　
1808
13
[He] 2s2 2p1
8.298
6　
12.0107
Carbon
C
3500
4827
2.26
0.094
ancient
14
[He] 2s2 2p2
11.2603
7　
14.0067
Nitrogen
N
-210
-196
1.25　
1772
15
[He] 2s2 2p3
14.5341
8　
15.9994
Oxygen
O
-218
-183
1.43
46.71
1774
16
[He] 2s2 2p4
13.6181
9　
18.9984
Fluorine
F
-220
-188
1.7
0.029
1886
17
[He] 2s2 2p5
17.4228
10　
20.1797
Neon
Ne
-249
-246
0.9　
1898
18
[He] 2s2 2p6
21.5645
11　
22.9897
Sodium
Na
98
883
0.97
2.75
1807
1
[Ne] 3s1
5.1391
12　
24.305
Magnesium
Mg
639
1090
1.74
2.08
1755
2
[Ne] 3s2
7.6462
13　
26.9815
Aluminum
Al
660
2467
2.7
8.07
1825
13
[Ne] 3s2 3p1
5.9858
14　
28.0855
Silicon
Si
1410
2355
2.33
27.69
1824
14
[Ne] 3s2 3p2
8.1517
15　
30.9738
Phosphorus
P
44
280
1.82
0.13
1669
15
[Ne] 3s2 3p3
10.4867
16　
32.065
Sulfur
S
113
445
2.07
0.052
ancient
16
[Ne] 3s2 3p4
10.36
17　
35.453
Chlorine
Cl
-101
-35
3.21
0.045
1774
17
[Ne] 3s2 3p5
12.9676
18　
39.948
Argon
Ar
-189
-186
1.78　
1894
18
[Ne] 3s2 3p6
15.7596
19　
39.0983
Potassium
K
64
774
0.86
2.58
1807
1
[Ar] 4s1
4.3407
20　
40.078
Calcium
Ca
839
1484
1.55
3.65
1808
2
[Ar] 4s2
6.1132
21　
44.9559
Scandium
Sc
1539
2832
2.99　
1879
3
[Ar] 3d1 4s2
6.5615
22　
47.867
Titanium
Ti
1660
3287
4.54
0.62
1791
4
[Ar] 3d2 4s2
6.8281
23　
50.9415
Vanadium
V
1890
3380
6.11　
1830
5
[Ar] 3d3 4s2
6.7462
24　
51.9961
Chromium
Cr
1857
2672
7.19
0.035
1797
6
[Ar] 3d5 4s1
6.7665
25　
54.938
Manganese
Mn
1245
1962
7.43
0.09
1774
7
[Ar] 3d5 4s2
7.434
26　
55.845
Iron
Fe
1535
2750
7.87
5.05
ancient
8
[Ar] 3d6 4s2
7.9024
27　
58.9332
Cobalt
Co
1495
2870
8.9　
1735
9
[Ar] 3d7 4s2
7.881
28　
58.6934
Nickel
Ni
1453
2732
8.9
0.019
1751
10
[Ar] 3d8 4s2
7.6398
29　
63.546
Copper
Cu
1083
2567
8.96　
ancient
11
[Ar] 3d10 4s1
7.7264
30　
65.39
Zinc
Zn
420
907
7.13　
ancient
12
[Ar] 3d10 4s2
9.3942
31　
69.723
Gallium
Ga
30
2403
5.91　
1875
13
[Ar] 3d10 4s2 4p1
5.9993
32　
72.64
Germanium
Ge
937
2830
5.32　
1886
14
[Ar] 3d10 4s2 4p2
7.8994
33　
74.9216
Arsenic
As
81
613
5.72　
ancient
15
[Ar] 3d10 4s2 4p3
9.7886
34　
78.96
Selenium
Se
217
685
4.79　
1817
16
[Ar] 3d10 4s2 4p4
9.7524
35　
79.904
Bromine
Br
-7
59
3.12　
1826
17
[Ar] 3d10 4s2 4p5
11.8138
36　
83.8
Krypton
Kr
-157
-153
3.75　
1898
18
[Ar] 3d10 4s2 4p6
13.9996
37　
85.4678
Rubidium
Rb
39
688
1.63　
1861
1
[Kr] 5s1
4.1771
38　
87.62
Strontium
Sr
769
1384
2.54　
1790
2
[Kr] 5s2
5.6949
39　
88.9059
Yttrium
Y
1523
3337
4.47　
1794
3
[Kr] 4d1 5s2
6.2173
40　
91.224
Zirconium
Zr
1852
4377
6.51
0.025
1789
4
[Kr] 4d2 5s2
6.6339
41　
92.9064
Niobium
Nb
2468
4927
8.57　
1801
5
[Kr] 4d4 5s1
6.7589
42　
95.94
Molybdenum
Mo
2617
4612
10.22　
1781
6
[Kr] 4d5 5s1
7.0924
43
*
98
Technetium
Tc
2200
4877
11.5　
1937
7
[Kr] 4d5 5s2
7.28
44　
101.07
Ruthenium
Ru
2250
3900
12.37　
1844
8
[Kr] 4d7 5s1
7.3605
45　
102.9055
Rhodium
Rh
1966
3727
12.41　
1803
9
[Kr] 4d8 5s1
7.4589
46　
106.42
Palladium
Pd
1552
2927
12.02　
1803
10
[Kr] 4d10
8.3369
47　
107.8682
Silver
Ag
962
2212
10.5　
ancient
11
[Kr] 4d10 5s1
7.5762
48　
112.411
Cadmium
Cd
321
765
8.65　
1817
12
[Kr] 4d10 5s2
8.9938
49　
114.818
Indium
In
157
2000
7.31　
1863
13
[Kr] 4d10 5s2 5p1
5.7864
50　
118.71
Tin
Sn
232
2270
7.31　
ancient
14
[Kr] 4d10 5s2 5p2
7.3439
51　
121.76
Antimony
Sb
630
1750
6.68　
ancient
15
[Kr] 4d10 5s2 5p3
8.6084
52　
127.6
Tellurium
Te
449
990
6.24　
1783
16
[Kr] 4d10 5s2 5p4
9.0096
53　
126.9045
Iodine
I
114
184
4.93　
1811
17
[Kr] 4d10 5s2 5p5
10.4513
54　
131.293
Xenon
Xe
-112
-108
5.9　
1898
18
[Kr] 4d10 5s2 5p6
12.1298
55　
132.9055
Cesium
Cs
29
678
1.87　
1860
1
[Xe] 6s1
3.8939
56　
137.327
Barium
Ba
725
1140
3.59
0.05
1808
2
[Xe] 6s2
5.2117
57　
138.9055
Lanthanum
La
920
3469
6.15　
1839
3
[Xe] 5d1 6s2
5.5769
58　
140.116
Cerium
Ce
795
3257
6.77　
1803
101
[Xe] 4f1 5d1 6s2
5.5387
59　
140.9077
Praseodymium
Pr
935
3127
6.77　
1885
101
[Xe] 4f3 6s2
5.473
60　
144.24
Neodymium
Nd
1010
3127
7.01　
1885
101
[Xe] 4f4 6s2
5.525
61
*
145
Promethium
Pm
1100
3000
7.3　
1945
101
[Xe] 4f5 6s2
5.582
62　
150.36
Samarium
Sm
1072
1900
7.52　
1879
101
[Xe] 4f6 6s2
5.6437
63　
151.964
Europium
Eu
822
1597
5.24　
1901
101
[Xe] 4f7 6s2
5.6704
64　
157.25
Gadolinium
Gd
1311
3233
7.9　
1880
101
[Xe] 4f7 5d1 6s2
6.1501
65　
158.9253
Terbium
Tb
1360
3041
8.23　
1843
101
[Xe] 4f9 6s2
5.8638
66　
162.5
Dysprosium
Dy
1412
2562
8.55　
1886
101
[Xe] 4f10 6s2
5.9389
67　
164.9303
Holmium
Ho
1470
2720
8.8　
1867
101
[Xe] 4f11 6s2
6.0215
68　
167.259
Erbium
Er
1522
2510
9.07　
1842
101
[Xe] 4f12 6s2
6.1077
69　
168.9342
Thulium
Tm
1545
1727
9.32　
1879
101
[Xe] 4f13 6s2
6.1843
70　
173.04
Ytterbium
Yb
824
1466
6.9　
1878
101
[Xe] 4f14 6s2
6.2542
71　
174.967
Lutetium
Lu
1656
3315
9.84　
1907
101
[Xe] 4f14 5d1 6s2
5.4259
72　
178.49
Hafnium
Hf
2150
5400
13.31　
1923
4
[Xe] 4f14 5d2 6s2
6.8251
73　
180.9479
Tantalum
Ta
2996
5425
16.65　
1802
5
[Xe] 4f14 5d3 6s2
7.5496
74　
183.84
Tungsten
W
3410
5660
19.35　
1783
6
[Xe] 4f14 5d4 6s2
7.864
75　
186.207
Rhenium
Re
3180
5627
21.04　
1925
7
[Xe] 4f14 5d5 6s2
7.8335
76　
190.23
Osmium
Os
3045
5027
22.6　
1803
8
[Xe] 4f14 5d6 6s2
8.4382
77　
192.217
Iridium
Ir
2410
4527
22.4　
1803
9
[Xe] 4f14 5d7 6s2
8.967
78　
195.078
Platinum
Pt
1772
3827
21.45　
1735
10
[Xe] 4f14 5d9 6s1
8.9587
79　
196.9665
Gold
Au
1064
2807
19.32　
ancient
11
[Xe] 4f14 5d10 6s1
9.2255
80　
200.59
Mercury
Hg
-39
357
13.55　
ancient
12
[Xe] 4f14 5d10 6s2
10.4375
81　
204.3833
Thallium
Tl
303
1457
11.85　
1861
13
[Xe] 4f14 5d10 6s2 6p1
6.1082
82　
207.2
Lead
Pb
327
1740
11.35　
ancient
14
[Xe] 4f14 5d10 6s2 6p2
7.4167
83　
208.9804
Bismuth
Bi
271
1560
9.75　
ancient
15
[Xe] 4f14 5d10 6s2 6p3
7.2856
84
*
209
Polonium
Po
254
962
9.3　
1898
16
[Xe] 4f14 5d10 6s2 6p4
8.417
85
*
210
Astatine
At
302
337　　
1940
17
[Xe] 4f14 5d10 6s2 6p5
9.3
86
*
222
Radon
Rn
-71
-62
9.73　
1900
18
[Xe] 4f14 5d10 6s2 6p6
10.7485
87
*
223
Francium
Fr
27
677　　
1939
1
[Rn] 7s1
4.0727
88
*
226
Radium
Ra
700
1737
5.5　
1898
2
[Rn] 7s2
5.2784
89
*
227
Actinium
Ac
1050
3200
10.07　
1899
3
[Rn] 6d1 7s2
5.17
90　
232.0381
Thorium
Th
1750
4790
11.72　
1829
102
[Rn] 6d2 7s2
6.3067
91　
231.0359
Protactinium
Pa
1568　
15.4　
1913
102
[Rn] 5f2 6d1 7s2
5.89
92　
238.0289
Uranium
U
1132
3818
18.95　
1789
102
[Rn] 5f3 6d1 7s2
6.1941
93
*
237
Neptunium
Np
640
3902
20.2　
1940
102
[Rn] 5f4 6d1 7s2
6.2657
94
*
244
Plutonium
Pu
640
3235
19.84　
1940
102
[Rn] 5f6 7s2
6.0262
95
*
243
Americium
Am
994
2607
13.67　
1944
102
[Rn] 5f7 7s2
5.9738
96
*
247
Curium
Cm
1340　
13.5　
1944
102　
5.9915
97
*
247
Berkelium
Bk
986　
14.78　
1949
102　
6.1979
98
*
251
Californium
Cf
900　
15.1　
1950
102　
6.2817
99
*
252
Einsteinium
Es
860　　　
1952
102　
6.42
100
*
257
Fermium
Fm
1527　　　
1952
102　
6.5
101
*
258
Mendelevium
Md　　　　
1955
102　
6.58
102
*
259
Nobelium
No
827　　　
1958
102　
6.65
103
*
262
Lawrencium
Lr
1627　　　
1961
102　
4.9
104
*
261
Rutherfordium
Rf　　　　
1964
4　　
105
*
262
Dubnium
Db　　　　
1967
5　　
106
*
266
Seaborgium
Sg　　　　
1974
6　　
107
*
264
Bohrium
Bh　　　　
1981
7　　
108
*
277
Hassium
Hs　　　　
1984
8　　
109
*
268
Meitnerium
Mt　　　　
1982
9　　
　
