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radioactivity

the result of a natural change of an isotope of one element into an isotope of a different element

alpha rays

stream of positively charged particles (alpha particles) they have a +2 charge and a mass of 4 amu

beta rays

composed of a stream of negatively charged particles (beta particles) that have properties similar to an electron

gamma rays

consists of electromagnetic radiation of very short wavelengths (high frequency and high energy) most dammaging of radioactive particles

nuclear reaction

results from radioactivity

nucleons

protons and neutrons

alpha emitters

atoms that undergo radioactive decay resulting in the release of an alpha particle

beta emitters

nuclei of atoms that undergo emission of beta particles

gamma rays

highly energetic photons (excess energy released from an alpha or beta particle)

positron

particle equal in mass but opposite of charge to an electron (emission = decrease of atomic number by one)

stable isotope

does not spontaneously decompose into a different element
1. most stable when the number of neutrons is equal to or greater than the number of protons with exception to H-1 and He-3
2. elements with low atomic numbers, the number of neutrons is almost equal to the number of protons
3. nuclear stability is greater for isotopes that contain even numbers of protons and neutrons

half life

the period of the time required for exactly one half of the number of atoms in the original sample to undergo a radioactive decay, forming a new element

fission

splitting of heavy nuclei into smaller nuclei releasing large amounts of energy in the process

fusion

energy releasing combination of light nuclei forming heavier ones

critical mass

the size of a sample that is large enough to self-sustain a chain reaction

plasma

forms when atoms are stripped of their electrons, which results in positively charged nuclei

octet rule

a noble gas electron configuration

lewis dot symbols

determining direction of electron transfer

electrostatic forces

forces between particles caused by their differences in electric charges (ionic bond) --> form and ionic compound

crystal lattice

the attraction of oppositely charged ions allows them to settle into this structure

salts

neutral ionic compounds formed from metal ions (cations) and nonmetal ions (anions)

chemical nomenclature

the system that scientists use for naming ionic and molecular compounds

binary compounds

ionic compounds consisting of two atoms

covalent bond

atoms share some or all their valence electrons in such a manner as to achieve a noble gas configuration

molecular formula

used when referring to covalently bonded compounds

double bond

results when two atoms share four electrons

triple bond

forms when six electrons are shared between two atoms

bond energy

the energy to break bonds between a specific pair of atoms

electronegativity

the ability of an atom during bond formation to attract electrons from its bonding partner

polar covalent bond

electrons are not shared equally

polarity

strength of a polar bond (based on the differences in electronegativities of the atoms involved in bonding

valence shell electron pair repulsion theory

(VSEPR) the groups of electrons arrange themselves about the central atom in such a way that lowers the molecules overall energy

central atom

the atom in a molecule to which all other atoms are bonded

electron pair shape

this includes the unbonded electron pair connected to the central atom
1. linear (180)
2. trigonal planar (120)
3. tetrahedral (109.5)

molecular shape

ignoring the unbonded electron pair connected to the central atom

electrolytes

compounds that conduct electricity when melted or dissolved in water

intermolecular forces

attractions between individual molecules

dipole dipole forces

forces between polar molecules

hydrogen bonding

result of the strong interaction between a hydrogen atom and N, O, or F

solids

fixed shape and volume, non compressible

liquids

variable shape, fixed volume, non-compressible

gases

variable shape and volume, easily compressed

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