Ch2 - Atoms and Elements Flashcards
(26 cards)
ion
a particle with unequal numbers of protons and electrons. This results in the particle having an electric charge
cation
positive ions formed when atoms lose one or more electrons
anion
negative ions formed when atoms gain one or more electrons
who discovered the electron and how?
JJ Thomson discovered the electron in the late 1800s while studying the properties of cathode rays.
who first proposed that matter was composed of small indestructible particles?
Leucippus and Democritus first proposed this in the 5th century BC
who calculated the charge and mass of the electron?
Robert Millikan calculated this in his oil drop experiment in 1909
who discovered radioactivity and which three types did they identify?
Henri Becquerel and Marie Curie discovered radioactivity in the late 1800s. They identified alpha, beta, and gamma rays.
who proposed the Plum Pudding model of the atom?
JJ Thompson
who proposed the nuclear theory of the atom?
Ernest Rutherford proposed this model after disproving the plum pudding model with his gold foil experiment.
three parts of the nuclear model
- a tiny nucleus contains all of an atom’s positive charge and nearly all of its mass
- most of an atom is empty space throughout which tiny negatively charged electrons are dispersed
- an atom contains equal numbers of protons and electrons so that atoms are electrically neutral
who discovered neutrons?
James Chadwick
how is 1 AMU defined?
1/12 the mass of carbon-12
isotopes
atoms of the same element with different numbers of neutrons
Natural Abundance
the relative amounts of each isotope expressed as a percentage
atomic weight
a weighted average of the masses of isotopes of a given element
who proposed the modern periodic table?
Dmitri Mendeleev, in the 1800s
periodic law
a summary of Mendeleev’s observations of certain properties that repeat as you arrange elements in order of increasing mass
each horizontal row in the periodic table is called what?
a period
each vertical column in the periodic table is called what?
a group or family
elements in a given family have similar what?
chemical properties
elements in group 1 are called what?
alkali metals
elements in group 2 are called what?
alkaline earth metals
elements in group 17 are called what?
halogens
elements in group 18 are called what?
noble gases
