Unit 1: Atomic Structure Flashcards
the fundamental building blocks of matter
atoms
subatomic particles that make up an atom
protons
neutrons
electrons
particles in the nucleus
protons and neutrons
define atomic number:
number of protons in an atom’s nucleus
define atomic mass:
the combined mass of protons, neutrons, and electrons
define atomic weight:
total number of protons and neutrons in the nucleus
define Z number:
number of protons in an atom’s nucleus (another name for atomic number)
define valence shell:
the outermost shell of an atom
define valence electrons:
electrons located in the outermost shell
stable atoms are electrically:
neutral
define ionization:
addition or removal of an electron
define the Octet rule:
the max number of electrons allowed in the valence shell of an atom is 8
types of ionizing radiation:
particulate (alpha and beta)
electromagnetic (x-ray and gamma ray)
define particulate radiation:
release of particles from the nucleus
define alpha particles:
particles that have 2 protons, 2 neutrons, and 0 electrons
atomic mass number of alpha particles and what kind of charge they contain:
4
+2 (double positive charge)
energy, range, and origin of alpha particles:
4-7 MeV
1-10 cm in air
heavy radioactive nuclei
define alpha emission:
throwing out neutrons or protons from the nucleus of a heavy atom
define beta particles:
particles emitted from the nucleus that resemble electrons
atomic mass number of beta particles and what kind of charge they contain:
0
-1 or +1 (neg. or pos. charged)
energy, range, and origin of beta particles:
0-7 MeV
0-10 meters in air
radioactive nuclei
Which form of particulate radiation can be stopped with a piece of paper? aluminum?
alpha; beta
Which form of ionizing radiation is the most damaging? least?
alpha; beta
list one thing that distinguishes a gamma ray from an x-ray:
origin
x-rays originate in the:
electron shells
gamma rays originate in the:
nucleus
list two things that distinguish alpha and beta particles from x-rays:
- particles originate in the nucleus
- particles can be slowed down
3 atomic forces that influence the behavior of the fundamental particles:
- strong nuclear force
- centripetal force
- centrifugal force
define strong nuclear force:
force of attraction between protons and neutrons (strongest attractive force)
protons could not live in the nucleus without the force of attraction with the neutrons
true
define centripetal force:
force between the nucleus and the electrons (neg. electrons are pulled towards the pos. nucleus)
define centrifugal force:
force involving just the electrons where it pulls them away from the nucleus
Types of energy:
- nuclear binding energy
- electron binding energy
- kinetic energy of electrons
define nuclear binding energy:
minimum energy required to disassemble the nucleus into its component parts
define electron binding energy:
energy required to keep electrons within their orbital shells
electron binding energy depends on what 2 factors?
distance from nucleus
total number of electrons within the atom
K-shell binding energies increase as:
atomic number (Z) increases
as electron shell radius increases:
electron velocity increases
electrons in outer orbits travel:
faster
define radioactivity; what it’s measured in:
the rate of decay of radioactive material
Becquerels
what makes an atom stable?
if the forces amongst the particles in the nucleus are balanced
what makes an atom unstable?
if the forces in the nucleus are unbalanced; or if the nucleus has an excess of internal energy
what does an unstable radioactive atom do to reach stability?
throw off protons or neutrons (nucleons) and particles, or by releasing energy
define radioactive decay:
process where atoms with unstable nuclei emit excess energy
define radionuclides:
nuclear arrangement resulting in radioactivity
define radioactive half-life:
time required for an amount of radioactivity to be reduced to one-half of the original value
represented as T1/2
