radioactivity Flashcards
what is the basic structure of an atom
a postively charged nucleus composed of protons and neutrons surrounded by negatively charged electrons
where is most of the mass of an atom concentrated
nucleus
how can the electron arrangements of the nucleus change
the absorption of the electromagnetic radiation that causes electrons to move further from the nucleus, the emission of electromagnetic radiation causes electrons to move closer
what is the mass number
the number of protons and neutrons in an atom
why do atoms have no overall charge
the number of electrons is equal to the number of protons
what is atomic number
thr number of protons in tje nucleus
what is the radius of an atom
0.1nm or 0.1x10to the power of-3m
what is the radius of a nucleus
1x10 to the power of-14m
what is the mass of protons and neutrons
1
what is the mass of electrons
negligible
what are isotopes
atoms of the same element with diffefent numbers of neutrons
how do atoms form positive ions
they lose one or more electrons
what model of the atom was developed following the discovery of the electron
plum pudding model
describe the plum pudding model of the atom
ball of positive. harge with negative electrons embedded in it
what was concluded from the alpha particle scattering experiment
the mass of the atom was concentrated at the centre and the nucleus was charged
what model replaced the plum pudding model
nuclear model
how did neils bohr adapt the nuclear model
he suggested that electrons orbit the nucleus at specific distances
what did the experimental work of james chadwick prove
the existancw of neutrons in the nucleus
what is radioactive decay
the random process by which the nucleus gives out radiation to become stable
what is activity
the rate at which a source of unstable nuclei decay
what is the unit for activity
becquerel, Bq
what is count rate
the number of decays recorded each second by a detector
what is an alpha particle
a helium nucleus which is two neutrons and two protons
what is a beta particle
a high speed electron ejected from the nucleus as a neutron turns into a proton
what is a gamma ray
electromagnetic radiation from the nucleus
what is half life
the time it takes for the number of nuclei of the isotope in a sample to half
what is contamination
tje unwanted prescence of materials containing radioactive atoms on other materials
what is irradiation
the process of exposing an object to nuclear radiation, the irradiated object does not become radioactive
