Sr Atomic Number

Chapter30 Sample Multiple Choice Problems

1.The atomicmass unit is defined as

1. Strontium (atomic number 38, symbol Sr) is an alkaline earth metal that is commercially available. Its chemical and physical properties are similar to that of elements such as barium and calcium.
2. The alkaline earth metal strontium (38 Sr) has four stable, naturally occurring isotopes: 84 Sr (0.56%), 86 Sr (9.86%), 87 Sr (7.0%) and 88 Sr (82.58%). Its standard atomic weight is 87.62(1). Only 87 Sr is radiogenic; it is produced by decay from the radioactive alkali metal 87 Rb, which has a half-life of 4.88 × 10 10 years (i.e.
3. Generic names and symbols are given to artificially produced elements which have been reported but not yet assigned official names.These names and symbols are assembled from the digits in the atomic number of the element, plus the ending -ium.

Atomic Number of Strontium Atomic Number of Strontium is 38. Chemical symbol for Strontium is Sr. Number of protons in Strontium is 38. Atomic weight of Strontium is 87.62 u or g/mol. Melting point of Strontium is 769 °C and its the boiling point is 1384 °C.

a.the mass of a proton.

b.the mass of an electron.

c.the mass of a hydrogen-1 atom.

d.one twelfth the mass of a carbon-12 atom.

2.An elementwith atomic mass number of 14 and atomic number 6 has how many neutrons?

a.6

b.8

c.14

d.20

3.Isotopes of anelement have nuclei with

a.the same number of protons, but differentnumbers of neutrons.

b.the same number of protons, and the samenumber of neutrons.

c.a different number of protons, and adifferent number of neutrons.

d.a different number of protons, and thesame number of neutrons.

4.If an atom'satomic number is given by Z, its atomic mass by A, and its neutron number

by N, whichof the following is correct?

a.N = A + Z

b.N = Z - A

c.N = A - Z

d.None of the above is correct.

5. In a {93/41}Nbnucleus, the number of protons, neutrons, and electrons is

a.41, 52, 93

b.41, 52, 52

c.41, 52, 41

d.41, 52, 0

6.The bindingenergy per nucleon

a.increases steadily as we go to heavierelements.

b.decreases steadily as we go to heavierelements.

c.is approximately constant throughout theperiodic table, except for very light nuclei.

d.has a maximum near iron in the periodictable.

7.An alpha particleis also known as

a.an electron.

b.a positron.

c.a helium nucleus.

d.a photon.

8.A beta^- particleis also known as

a.an electron. b.a positron.

c.a helium nucleus.

d.a photon.

9.The existenceof the neutrino was postulated in order to explain

a.alpha decay.

b.gamma emission.

c.beta decay.

d.fission.

10.When an alphaparticle is emitted from an unstable nucleus, the atomic mass number

of thenucleus

a.increases by 2.

b.decreases by 2.

c.increases by 4.

d.decreases by 4.

e.none of the above.

11.If 4.0X1018atoms decay with a half-life of 2.3 years, how many are remaining

after 3.7years?

a.2.5X1018

b.1.7X1018

c.1.3X1018

d.1.1X1018

12.A radioactivesample has a half-life of 5.0 min.Whatfraction of the sample is left

after 20min?

a.1/2

b.1/4

c.1/8

d.1/16

13.The half-lifeof radioactive iodine-137 is 8.0 days.How many iodine nuclei are

necessary to produce an activity of 1.0 micro-Ci?

a.2.9X109

b.4.6X109

c.3.7X1010

What Is Sr Atomic Number

d.7.6X1012

14.What happens tothe half-life of a radioactive substance as it decays?

a.It remains constant.

b.It increases.

c.It decreases.

d.It could do any of these.

15.The mass of {90/38}Sr is 89.907737 u and the mass of theatom its beta decays to is
89.907151 u. What is the energyreleased in the decay?

a. 1.2 MeV

b. 112 keV

c.0.546 MeV

Atomic Number Calculator

d.1.8 MeV

1.d 2.b

3.a

4.c

5.d

6.d

7.c

8.a

9.c

10.d

11.c

12.d

13.c

14.a

15.c