Ch 4 and 25 chem

Explain how to determine the number of neutrons an atom contains if you know its mass number and its atomic number

Number of neutrons-mass number-atomic number

What particles are found in the nucleus of an atom. What is the net charge of the nucleus?

Protons and neutrons are found in the nucleus of an atom; the net charge of the nucleus is a positive charge.

Which subatomic particles account for most all of an atom's mass?

Protons and neutrons.

What subatomic particles are involved in nuclear reactions?

Protons,electrons, and neutrons

How many protons and electrons are contained in an atom of element 44?

11 and 7

Explain how energy loss and nuclear stability are related to radioactive decay.

Radioactivity results when unstable nuclei emit energy in order to gain stability

The half-life of polonium-218 is 3.0 minutes. If you start with 20.0 g, how long will it be before only 1.0 g remains?

12.966 min

Why are some radioisotopes found in nature, while others are not?

Radioisotopes in nature have very long half lives. Short lived radioisotopes decay too quickly to exist in significant quantities

Based on the table, an atom of neon found in nature would most likely have a mass of ___________. a. 19.992 amu c. 20.994 amu b. 20.179 amu d. 21.991 amu

19.992 amu

In which of the neon isotopes is the number of neutrons the same as the number of protons? a. 20Ne b. 21Ne c. 22Ne d. none of the above

20Ne

Write a balanced nuclear equation for the alpha decay of americium-241

241/95 Am ---4/2He+ 237/93Np

Geologists use the decay of potassium-40 in volcanic rocks to determine their age. Potassium-40 has a half-life of 1.26 x 109 years, so it can be used to date very old rocks. If a sample of rock 3.15x108 years old contains 2.73 x 10-7g of potassium-40 today, how much potassium-40 was originally present in the rock? a. 2.30 x 10-7 g c. 3.25 x 10-7 g b. 1.71 x 10-8 g d. 4.37 x 10-6 g

3.25 x 10-7 g

Manganese-56 decays by beta emission and has a half life of 2.6 hours. If 0.625 mg exists after 24 hours of decay, how much Manganese-56 was in the original sample before the beta emission?

375.31mg

A carbon atom has a mass number of 12 and an atomic number of 6. How many neutrons does it have?

6 neutrons

126/52Te has _____________________. a. 126 neutrons, 52 protons, and 52 electrons b. 74 neutrons, 52 protons, and 52 electrons c. 52 neutrons, 74 protons, and 74 electrons d. 52 neutrons, 126 protons, and 126 electrons.

74 neutrons, 52 protons, and 52 electrons

Write a balanced nuclear equation for the beta decay of bromine-84

84/35Br --- 0/-1B + 84/36 Kr

What is the charge of the nucleus and name of element 89?

89+actinium

Technetium-104 has a half- life of 18.0 minutes. How much of a 165.0 g sample remains after 90 minutes?

%.156g

What is radioactive decay series ? When does the decay series end?

A family of decay reactions that continue until a stable, non radioactive isotope is formed

Explain what must occur before a radioactive atom ceases to undergo further radioactive decay.

A stable nonradioactive atom must form

Why is carbon-14 dating limited to objects that are approximately 24,000 years old or less?

After 24,000 years (~5 half life) only about 3% of the original C-14 remains. Amounts less than this are difficult to measure

What change in mass number occurs when a radioactive atom emits an alpha particle? A beta particle? A gamma particle?

Alpha- mass number decreases by 4 Beta: No change in mass number Gamma: no change in mass number

Define the atomic mass unit (amu). What were the benefits of developing the atomic mass unit as a standard unit of mass?

Amu= 1/12 of the mass of a C-12 atom. Scientists defined the atomic mass unit as a relative standard that was closer in size to atomic and subatomic mass.

Which subatomic particle was discovered by researchers working with cathode ray tubes?

At the time when Democritus lived, controlled experiments in regard to what held atoms together were impossible. That is why Democritus was unable to experimentally verify his ideas.

In writing a balance nuclear equation, what must be conserved?

Atomic number and mass number

Based on its position relative to the band of stability, Zn-80 will undergo __________________. a. Beta decay c. Electron Capture b. Position Emission d. All of the above

Beta decay

Boron-10 and Boron-11 are the naturally occurring isotopes of elemental boron. If boron has an atomic mass of 10.81 amu, which isotope occurs in greater abundance? Explain

Boron -11 must occur in greater abundance because the atomic weight of bromine is much closer to the mass of Boron -11 than to the mass of B-10

An atom of plutonium _______________________. a. Can be divided into smaller particles that retain all the properties of plutonium b. Cannot be divided into smaller particles that retain all the properties of plutonium. c. Does not possess all the properties of a larger quantity of plutonium. d. Cannot be seen using current technology.

Cannot be divided into smaller particles that retain all the properties of plutonium.

Who originally proposed the concept that matter was composed of tiny indivisible particles?

Democritus originally proposed the concept that matter was composed of tiny indivisible particles

How do isotopes of a given element differ? How are they similar?

Differ in the number of neutron and mass number. Similar in their chemical properties and the number of protons and electrons

The half-life of tritium ( ) is 12.3 years. If 48.0 mg of tritium is released from a nuclear power plant during the course of a mishap, what mass of the nuclide will remain after 49.2 years?

EA=BA ½ t/t1/2 3.0mg

Element X has an unstable nucleus due to an over-abundance of neutrons. All of the following are likely to occur EXCEPT__________________________. a. Element X will undergo radioactive decay. b. Element X will eventually become stable, nonradioactive element. c. Element X will gain more protons to balance the neutrons it possesses d. Element X will spontaneously lose energy.

Element X will gain more protons to balance the neutrons it possesses

The volume of an atom is made up mostly of _______________________________ a. Protons b. Neutrons c. Electrons d. Empty Space

Empty space

Explain the relationship between an atom's neutron-to-proton ratio and its stability.

For smaller atoms, the n/p ratio of stable isotopes is about 1:1. As atoms become larger, n/p ratio increases to about 1:51 . isotopes with ratios outside these values are likely to be radioactive.

Describe the flow of a cathode ray inside a cathode ray tube

From cathode to anode

What is the significance of the band of stability?

Isotopes lying outside the band will spontaneously decay

Calcium 35 will undergo positron emission because _____________________. a. It lies above the line of stability b. It lies below the line of stability c. It has a high neutron-to-proton ratio. d. It has an overabundance of neutrons.

It lies below the line of stability

Whose work is credited with being the beginning of modern atomic theory?

John Dalton is credited with being the beginning of modern atomic theory.

Using your knowledge of Alpha, Beta and Gamma Radioactive Decay (Nuclear chemistry). Write the nuclear reaction for the following processes.

Mass contribution of Cr-50= (49.946)(0.0435=2.173amu Mass contribution of Cr-52=(51.941)(0.8379)= 43.521amu Mass contribution of Cr-53= (52.941)(0.0950)= 5.029amu Mass contribution of Cr- 54= (53.939)(0.0236)=1.273amu Atomic mass: 2.173+43.521+ A. Alpha decay of iridum-174 174/77Ir—170/75Re+ 4/2He B. Beta decay of platinum-199 199/78Pt—199/79Au+0/-1B

An isotope of mercury has 80 protons and 120 neutrons. What is the mass number of this isotope?

Mass number= 200

How is the mass number related to the number of protons and neutrons an atom has?

Mass number=# of protons +number of neutrons

An isotope of xenon has an atomic number of 54 and contains 77 neutrons. What is the xenon isotope's mass number

Mass number=131

All of the following are beneficial applications of radioactivity EXCEPT __________________. a. Tracing the path of an element through a complex reaction b. Mutating genetic material using ionizing radiation. c. Diagnosing brain disorders using PET scans d. Destroying cancer cells with radiation therapy.

Mutating genetic material using ionizing radiation.

The immense amount of energy released by the Sun is due to which of the following reactions occurring within its core? a. Nuclear Fission b. Gamma Decay c. Nuclear Fusion d. Alpha Decay

Nuclear Fusion

Briefly describe the contributions of Roentgen, Becquerel, Rutherford to the field of nuclear chemistry.

Roentgen discovered x-rays Becquerel discovered ores that form film Rutherford discovered alpha , beta, gamma radiation

List the strengths and weaknesses of Rutherford's nuclear model of the atom.

Strengths: Rutherford's model explained the results of the gold foil experiment and why an atom is electronically neutral. Weaknesses: the model could not account for the total mass of an atom or the arrangement of the electrons

What is the charge and mass of a single electron?

The charge and mass of a single electron is charge=1- Mass=9.11X10⁻²⁸ g or 1/1840 of a hydrogen atom.

What caused the deflection of the alpha particles in Rutherford's gold foil experiment?

The concentrated positive charge in the nucleus caused the deflection of the alpha particles in Rutherford's gold foil experiment.

Explain what keeps the electrons confined in the space surrounding the nucleus?

The electrons are held within the atom by their attraction to the positively charged nucleus. That is what keeps the electrons confined in the space surrounding the nucleus. Attraction to positively charged nucleus.

Which of the following is not characteristic of a sample of a fissionable element capable of sustaining a chain reaction? a. The element has a mass of <60 b. The sample of the element possesses critical mass. c. The element's atoms have low binding energy per nucleon. d. The element's nuclei are more stable if split into smaller nuclei.

The element has a mass of <60

What is the primary factor determining whether or not an atom is stable or unstable?

The neutron to proton ratio

Explain why atoms are electrically neutral

The number of positively charged protons equals the negatively charged electrons.

Which outdated atomic model could be likened to chocolate chip cookie dough?

The plum pudding model

An atom has no net electrical charge because________________________. a. Its subatomic particles carry no electrical charges b. The positively charged protons cancel out the negatively charged neutrons. c. The positively charged neutrons cancel out the negatively charged electrons. d. The positively charged protons cancel out the negatively charged electrons.

The positively charged protons cancel out the negatively charged electrons.

What is the strong nuclear force? On what particles does it act?

The strong nuclear force binds nucleons together

What do the superscript and subscript in the notation 40/19K represent?

The superscript and the subscript in the notation represent 40= atomic mass 19= atomic number

How is an atom's atomic number related to its number of protons? To its number of electrons?

They are equal...# of protons=atomic number=#of electrons

All of the following are true of alpha particles EXCEPT___________________. a. They have the same composition as helium nuclei b. They carry a charge of 2+ c. They are more penetrating than B particles d. They are represented by the symbol 4/2He

They are more penetrating than B particles

What did the Curries contribute to the field of radioactivity and nuclear chemistry?

They discovered uranium as a source

Carbon- 12 Number of protons = 6 Number of neutrons = 6

n/p ratio 6/6 =1:1

Nickel-63 Number of protons = 28 Number of neutrons = 35

n/p ratio = 35/28 1:25:1

Calculate the neutron to proton ratio for each of the following atoms a. Tin-134 Number of protons = 50 Number of neutrons = 84

n/pratio = 84/50=1:68:1

What is a nucleon?

nucleon is a proton of neutron