2. Atoms & Elements

The following diagram is a representation of 20 atoms of a fictitious element, which we will call nevadium (Nv). The red spheres are 293Nv, and the blue spheres are 295Nv. (b) If the mass of 293Nv is 293.15 u and that of 295Nv is 295.15 u, what is the atomic weight of Nv?

The following diagram is a representation of 20 atoms of a fictitious element, which we will call nevadium (Nv). The red spheres are 293Nv, and the blue spheres are 295Nv. (a) Assuming that this sample is a statistically representative sample of the element, calculate the percent abundance of each element.

What is the atomic weight of an element that consists of two naturally occurring isotopes? The first isotope has a mass of 84.911 and an abundance of 72.17% and the second isotope has a mass of 86.909 and an abundance of 27.83%. (LO 2.15) (a) 85.47 (b) 86.35 (c) 85.91 (d) 85.17

(a) What isotope is used as the standard in establishing the atomic mass scale?

(b) Why is the atomic weight of carbon reported as 12.011 in the table of elements and the periodic table in the front inside cover of this text?

Iron has three major isotopes: 54Fe (atomic mass = 53.9396 u; abundance 5.85%), 56Fe (atomic mass = 55.9349 u; abundance 91.75%), and 57Fe (atomic mass = 56.9354 u; abundance 2.12 %). Calculate the atomic weight (average atomic mass) of iron.

Bromine has two naturally occurring isotopes, bromine-79 1atomic mass = 78.9183 u; abundance = 50.69%2 a n d bromine-81 1atomic mass = 80.9163 u; abundance = 49.31%2. Calculate the atomic weight of bromine.

An element has two naturally occurring isotopes. Isotope 1 has a mass of 120.9038 amu and a relative abundance of 57.4%, and isotope 2 has a mass of 122.9042 amu. Find the atomic mass of this element and identify it.

An element has four naturally occurring isotopes with the masses and natural abundances given here. Find the atomic mass of the element and identify it. Isotope Mass (amu) Abundance (%) 1 135.90714 0.19 2 137.90599 0.25 3 139.90543 88.43 4 141.90924 11.13

Bromine has two naturally occurring isotopes (Br-79 and Br-81) and has an atomic mass of 79.904 amu. The mass of Br-81 is 80.9163 amu, and its natural abundance is 49.31%. Calculate the mass and natural abundance of Br-79.

Bromine has two naturally occurring isotopes (Br-79 and Br-81) and has an atomic mass of 79.904 amu. The mass of Br-81 is 80.9163 amu, and its natural abundance is 49.31%. Calculate the mass and natural abundance of Br-79.

Silicon has three naturally occurring isotopes (Si-28, Si-29, and Si-30). The mass and natural abundance of Si-28 are 27.9769 amu and 92.2%, respectively. The mass and natural abundance of Si-29 are 28.9765 amu and 4.67%, respectively. Find the mass and natural abundance of Si-30.

The nucleus of 6Li is a powerful absorber of neutrons. It exists in the naturally occurring metal to the extent of 7.5%. In the era of nuclear deterrence, large quantities of lithium were processed to remove 6Li for use in hydrogen bomb production. The lithium metal remaining after removal of 6Li was sold on the market. (b) The atomic masses of 6Li and 7Li are 6.015122 and 7.016004 u, respectively. A sample of lithium depleted in the lighter isotope was found on analysis to contain 1.442% 6Li. What is the average atomic weight of this sample of the metal?

The element chromium (Cr) consists of four naturally occurring isotopes with atomic masses 49.9460, 51.9405, 52.9407, and 53.9389 u. The relative abundances of these four isotopes are 4.3, 83.8, 9.5, and 2.4%, respectively. From these data, calculate the atomic weight of chromium.

Copper (Cu) consists of two naturally occurring isotopes with masses of 62.9296 and 64.9278 u. (a) How many protons and neutrons are in the nucleus of each isotope? Write the complete atomic symbol for each, showing the atomic number and mass number. (b) The average atomic mass of Cu is 63.55 u. Calculate the abundance of each isotope.

What is the difference between an element's atomic number and its atomic weight?

There are two different isotopes of bromine atoms. Under normal conditions, elemental bromine consists of Br2 molecules, and the mass of a Br2 molecule is the sum of the masses of the two atoms in the molecule. The mass spectrum of Br2 consists of three peaks: Mass (u) Relative Size 157.836 0.2569 159.834 0.4999 161.832 0.2431 (b) What is the mass of each isotope?

Iodine has a lower atomic mass than tellurium (126.90 for iodine, 127.60 for tellurium) even though it has a higher atomic number (53 for iodine, 52 for tellurium). Explain.

Naturally occurring iodine has an atomic mass of 126.9045 amu. A 12.3849 g sample of iodine is accidentally contaminated with an additional 1.00070 g of 129I, a synthetic radioisotope of iodine used in the treatment of certain diseases of the thyroid gland. The mass of 129I is 128.9050 amu. Find the apparent 'atomic mass' of the contaminated iodine.

The unified atomic mass unit (u) 1/12 the mass of a neutral atom of: (a) 1^H (b) 12^C (c) 14^C (d) 16^O

(a) The unified atomic mass unit (u) is used to represent the extremely small mass of atoms. How many grams are equivalent to 1 u?

Boron has only two naturally occurring isotopes. The mass of boron-10 is 10.01294 amu and the mass of boron-11 is 11.00931 amu. Calculate the relative abundances of the two isotopes.

Lithium has only two naturally occurring isotopes. The mass of lithium-6 is 6.01512 amu and the mass of lithium-7 is 7.01601 amu. Calculate the relative abundances of the two isotopes.

Naturally occurring boron consists of two isotopes: 10^B (19.9%) with an isotopic mass of 10.0129 and 11^B (80.1%) with an isotopic mass of 11.009 31. What is the atomic weight of boron? Check your answer by looking at a periodic table.

Naturally occurring silver consists of two isotopes: 107^Ag (51.84%) with an isotopic mass of 106.9051 and 109^Ag (48.16%) with an isotopic mass of 108.9048. What is the atomic weight of silver? Check your answer in a periodic table.

Magnesium has three naturally occurring isotopes: 24^Mg (23.985) with 78.99% abundance, 25^Mg (24.986) with 10.00% abundance, and a third with 11.01% abundance. Look up the atomic weight of magnesium, and then calculate the mass of the third isotope.

Naturally occurring chlorine is composed of two isotopes: 75.76% Cl-35 (mass 34.9688 amu) and 24.24% Cl-37 (mass 36.9659 amu). Naturally occurring oxygen is composed of three isotopes: 99.757% O-16 (mass 15.9949 amu), 0.038% O-17 (mass 16.9991 amu), and 0.205% O-18 (mass 17.9991 amu). The compound dichlorine monoxide is composed of two chlorine atoms and one oxygen atom bonded together to form the Cl2O molecule. How many Cl2O molecules of different masses naturally exist? Give the masses of the three most abundant Cl2O molecules.

A sample of naturally occurring silicon consists of 28^Si (27.9769), 29^Si (28.9765), and 30^Si (29.9738). If the atomic weight of silicon is 28.0855 and the natural abundance of 29^Si is 4.68%, what are the natural abundances of 28^Si and 30^Si?

Silver is composed of two naturally occurring isotopes: Ag-107 (51.839%) and Ag-109. The ratio of the masses of the two isotopes is 1.0187. What is the mass of Ag-107?

Copper metal has two naturally occurring isotopes: copper-63 (69.15%; isotopic mass = 62.93) and copper-65 (30.85%; isotopic mass 64.93). Calculate the atomic weight of copper, and check your answer in the periodic table.

Germanium has five naturally occurring isotopes: 70^Ge, 20.5%, 69.924; 72^Ge, 27.4%, 71.922; 73^Ge, 7.8%, 72.923; 74^Ge, 36.5%, 73.921; and 76^Ge, 7.8%, 75.921. What is the atomic weight of germanium?

Prior to 1961, the atomic mass unit (amu) was defined as 1/16 the mass of the atomic weight of oxygen; that is, the atomic weight of oxygen was defined as exactly 16. What was the mass of a 12C atom prior to 1961 if the atomic weight of oxygen on today's scale is 15.9994?

Boron has two naturally occurring isotopes

What is the average atomic mass of titanium on that planet?

What is the relative atomic mass of a hypothetical element that consists of the following isotopes in the indicated natural abundances?

On another planet, the isotopes of titanium have the given natural abundances.