Chapter 12: Nuclear Phenomena

Question 1

Atomic number (Z):

Answer 1

always an integer and is equal to the number of protons in the nucleus

Question 2

Mass number (A):

Answer 2

equal to the total number of nucleons (protons and neutrons) in a nucleus.

Question 3

Isotopic notation:

Answer 3

immediately left to the chemical symbol, the mass number and atomic number can be read top to bottom, respectively.

Question 4

Isotopes:

Answer 4

atoms of the same element that have different mass numbers; same number of protons, different number of neutrons;

Isotopes generally exhibit the same chemical properties

Question 5

Radionuclide:

Answer 5

generic term used to refer to any radioactive isotope, especially those used in nuclear medicine

Question 6

The atomic mass of an atom is simply equal to:

Answer 6

its mass number (A)

Question 7

Atomic weight:

Answer 7

the mass in grams of one mole of atoms of a given element. Expressed g/mol

Question 8

Nuclear binding energy is:

Answer 8

the amount of energy that is released when nucleons (protons and neutrons) bind together through strong nuclear force

Question 9

Mass defect is:

Answer 9

the difference between the mass of the unbound constituents and the mass of the bound constituents in the nucleus

Question 10

Unbound constituents in the nucleus have:

Answer 10

more energy and more mass than the bound constituents

Question 11

Mass defect is the amount of mass converted to energy through:

Answer 11

the nuclear reactions of fusion or fission

Question 12

Fusion:

Answer 12

occurs when small nuclei combine into larger nuclei

Question 13

Fission:

Answer 13

occurs when a large nucleus splits into smaller nuclei; rarely spontaneous; when a nucleus absorbs a low energy neutron, a chain reaction can occur

Question 14

Energy is released in both fusion and fission because:

Answer 14

the nuclei formed in both processes are more stable than the starting nuclei

Question 15

Alpha decay is:

Answer 15

Loss of a 4-He nucleus (2 protons and 2 neutrons). Mass number decreases by 4 and atomic number decreases by 2.

Question 16

Beta decay is:

Answer 16

Loss of an electron (e- or β-). Emitted when a neutron in the nucleus decays into a proton and an antineutrino (β-). A neutron is lost and a proton takes its place. Mass number remains the same and atomic number increases by one.

Question 17

Positron decay is:

Answer 17

when a proton splits into a positron (β+) and a neutron. A proton is lost and the mass number remains the same.

Question 18

Gamma decay is :

Answer 18

the emission of a gamma photon. The energy of the parent nucleus is lowered, but the mass and atomic number remain the same.

Question 19

Electron capture is:

Answer 19

When a radionuclide captures an inner electron that combines with a proton to form a neutron. Atomic number is one less and mass number remains the same.

Question 20

Half-life is:

Answer 20

the amount of time required for half of a sample of radioactive nuclei to decay

T_1/2= ^0.693/_λ

Question 21

The rate at which radioactive nuclei decay is proportional to:

Answer 21

the number of nuclei that remain

Question 22

The more binding energy per nucleon released, the more:

Answer 22

stable the nucleus

Question 23

Equation for exponential decay:

Answer 23

n = n_oe^-λt

Question 24

Equation to determine the mass lost as binding energy in a nucleus:

Answer 24

E = mc²

where m is the mass of c is the speed of light

Question 25

When protons and neutrons come together to form the nucleus, they are attracted to each other by:

Answer 25

the strong nuclear force

Question 26

The most stable atom according to binding energy per nucleon is:

Answer 26

iron

in general, intermediate-sized nuclei are more stable than large and small nuclei