gen chem 1 ch 2

77 flashcards

List the "magic numbers" ; What do they mean
2, 8, 20, 28, 50, 82, 126; if an element has a "magic number" for its number of protons, neutrons, or both, then it's probably stable
Describe alpha particles
High-energy helium nuclei consisting of two protons and two neutrons
Describe beta particles
high-energy electrons
Describe positrons
particles with the same mass as an electron but with 1 unit of positive charge
Describe protons
nuclei of hydrogen atoms
Describe neutrons
Particles with a mass approximately equal to that of a proton but with no charge
Describe a gamma ray
Very high-energy electromagnetic radiation
A balanced chemical reaction equation reflects the fact that during a chemical reaction, bonds __, and atoms , but the total numbers of of each element are __
break and form; rearrange; atoms; conserved and do not change
A balanced nuclear reaction equation indicates that there is a rearrangement during a nuclear reaction, but of __, rather than __
nucleons; atoms
(Conversation laws of nuclear reactions) The sum of the mass numbers of the reactants equals the _____
sum of the mass numbers of the products
(Conversation laws of nuclear reactions) The sum of the charges (the atomic number - number of protons) of the reactants equals _____
the sum of the charges of the products
During a nucelar reaction, how to you calculate the sum of the charges?
the atomic number - number of protons
Define radioactive decay
the spontaneous change of an unstable nuclide into another
Define alpha (α) decay
the emission of an alpha particle from the nucleus
Define beta (β) decay
the emission of an electron from a nucleus
Gamma (γ) emission is observed when what happens?
when a nuclide is formed in an excited state and then decays into its ground (stable) state with the emission of a γ ray
Define positron emission (β^+ decay)
the emission of a positron from the nucleus
Define electron capture
process in which the nucleus captures one of the inner electrons in an atom
Give the change in mass/atomic numbers for alpha decay
A: decrease by 4 Z: decrease by 2
Give the change in mass/atomic numbers for beta decay
A: unchanged Z: increase by 1
Give the change in mass/atomic numbers for gamma decay
A: unchanged Z: unchanged
Give the change in mass/atomic numbers for positron emission
A: unchanged Z: decrease by 1
Give the change in mass/atomic numbers for electron capture
A: unchanged Z: decrease by 1
Which process decreases the neutron/proton ratio? (also type its representation)
Beta decay (Neutron ---> Proton + β^-)
Which 3 processes increase the neutron/proton ratio? (also type their representation)
proton emission (Proton ---> Neutron + β^+), electron capture (Proton + Electron ---> Neutron), and alpha decay
Define nuclear transmutation
the conversion of one nuclide into another
Give 2 examples of nuclear transmutation
The radioactive decay of a nucleus and reaction of a nucleus with another particle
How did Ernest Rutherford produce the first manmade nucleus in 1917? What did he find?
He bombarded nitrogen-14 with high speed α particles from a natural radioactive isotope of radium. He found that the formation of protons resulted from that reaction
Define nuclear fission
the breaking of a large nucleus into smaller pieces
During nuclear fission, the breaking (is/is not) random, forming a (small/large) number of (similar/different) products
is; large; different
Does nuclear fission happen naturally? What is required to occur for nuclear fission to happen?
No; requires bombardment with neutrons
When and where was the first reported instance of nuclear fission?
Germany 1939
Define chain reaction
repeated fission caused when the neutrons released infission bombard other atoms
Define nuclear fusion
the process of converting very light nuclei into heavier nuclei
Radioactive isotopes have the same __ as stable isotopes of the same element, but they emit __, which can be detected
chemical properties; radiation
List the 5 uses of radioisotopes in medicine
Locate damaged tissues in the heart, liver, and lungs; Monitor goiter and treat thyroid conditions; Monitor liver and brain tumors; Help locate obstructions to the flow of blood; Radiation therapy to damage the DNA of cancer cells
Define physical change
a change in the state or properties of matter without any accompanying change in chemical composition
List the 5 commercial uses of radioisotopes
Determine the thickness of films and thin metal sheets; Detect flaws in metal to be used in structures; Pest control; Food preservation; Ionization-type smoke detectors
List the 3 "Other" uses of radioisotopes
Labeling fertilizers in studies of nutrient uptake by plants and crop growth; Investigations of digestive and milk-producing processes in cows; Studies on the growth and metabolism of animals and plants
How can ultraviolet, X-ray, and Gamma rays impact the human body?
They can damage DNA
List the types of radiation in order from least to most penetrating
alpha < beta < neutron < gamma
Give the annual public dose limit of radiation (NRC)
100 millirems
Give the average us annual dose of radiation
620 millirems
Give the average nuclear service worker doses limit of radiation
5000 millirems
A chemical changes produces how many types of matter?
1 or more
Is the matter that a chemical change produces different from the matter present before the change?
Yes
A chemical change involves changes in the ____ of the matter present
electronic structure (electrons)
Does a chemical change involve changes to the atoms themselves?
No
A nuclear change involves changes to the _____ in matter
nuclei
A chemical change changes the way elements are ______
combined
A nuclear change changes an atom's ____
nucleus
(Chemical change) Different isotopes of an element have similar ____
chemical properties
Energy changes in chemical reactions are generally (small/large) in magnitude
small
(Chemical change) Only electrons in the ____ level of the atom are involved
outer level
In a chemical change, are new elements formed?
No
(Nuclear change) Different isotopes of an element have different ____
nuclear properties
Energy changes in nuclear reactions can be many orders of magnitude (smaller/larger) than chemical reactions
larger
Is the nucleus of an atom involved during nuclear change?
Yes
May elements be changed into new elements during nuclear change?
Yes
Define nuclear chemistry
the study of reactions that involve changes in nuclear structure
When referring to a single type of nucleus, the term _____ is often used. It is identified by what symbol?
nuclide; identified by an X with an A in the top left corner and an Z is the bottom left corner
Define nucleons
protons and neutrons, when referred to collectively
A strong nuclear force is the force of attraction that holds the ____ together
nucleus
Name the four fundamental forces known to exist
electromagnetic force, gravitational force, the strong nuclear force, and the nuclear weak force
Define mass defect
the loss in mass that occurs when protons and neutrons combine to form a nucleus
Define binding energy
the amount of energy holding a nucleus together
The (larger/smaller) the binding energy, the more (stable/unstable) the nucleus
larger; stable
Give the formula for calculating binding energy. State what the letters mean.
ΔE = Δmc² ; E is binding energy, m is the mass defect, c is the constant (speed of light)
Give the formula for calculating the mass of an atom
(# of protons x 1.0073 amu) + (# of neutrons x 1.0087 amu) + (# of electrons x 0.00055 amu)
A stable nucleus is one that (can/cannot) be transformed into another configuration without adding energy from the outside
cannot
Define the band of stability
the small band of stable isotopes on a plot of the number of neutrons vs the number of protons
Nuclei to the left or right of the band of stability are (stable/unstable) and exhibit _____
unstable; radioactivity
What happens to the nuclei that are to the left or to the right of the band of stability? What are these nuclei called?
they spontaneously decay into other nuclei that are either in, or closer to, the band of stability; radioisotope
Generally, the number of ___ is equal to or greater than the number of ___ in a stable nuclide
neutrons; protons
The number of neutrons to protons is nearly equal for elements of (high/low) atomic number
low
Explain why elements above atomic number 20 tend to have a higher ratio of neutrons to protons in a stable nuclide
The larger nuclei have more proton-proton repulsions, so they require a larger number of neutrons to provide compensating strong forces to overcome electrostatic repulsions and hold the nucleus together
Nuclides with (even/odd) numbers of protons, neutrons, or both tend to be stable
even