Development of AtomicTheory
Choose words from the list to fill in the blanks in the paragraphs.
Atom
Atomic number
Chadwick
Conservation of matter
Dalton
Definite proportions
Electron
Isotope
Lavoisier
Mass number
Multiple proportions
Neutron
Proton
Proust
Quantum
Rutherford
Subatomic number
Thomson
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More than 2000 years ago, Greek philosophers proposed the existence of very small, indivisible particles, each of which is called a(n) (1). The theory that such particles existed was supported, much later, by _ (2), who proposed, in his law of __ (3), that matter
(4) proposed, in his law of
cannot be created or destroyed. Then
_____(5), that the ratio of the masses of elements in any given compound is always the same. The law of ____(6), proposed soon after, states that the masses of one element that combine with fixed mass of another element in different compounds are in simple whole-number ratios. An atomic theory based on these laws was developed by ____ (7).
It was later proposed that the atom is not indivisible, but is made up of smaller particles, each of which is called ____ (8). These particles include the negatively charge ____ (9), discovered by ___ (10); the positively charged ____ (11); and the uncharged _____ (12); discovered by ____(13). The latter two particles were present in the _ (14), or center of the atom, which is discovered by __(15) in his gold-foil experiment.
The number of positively charged particles in an atom is called its ____(16). The total number of the positively charged and the uncharged particles is called the _ (17) of the atom. An atom that has the same number of positively charged particles as another atom, but a different number of uncharged particles, is called a(n) __(18)
Historical Development
Match the concept, theory, or discovery in Column I with the scientist most closely associated with it. Some scientists may be used more than once and some not at all.
Column IColumn II
______1.Determined that most of the atom is empty(a) Rutherford
______2.Worked extensively with cathode ray tubes(b) Becquerel
to decipher the structure of the atom
______3.Planetary model of the atom(c) Bohr
______4.Gold-foil experiment(d) Crooks
______5.Tried to explain the nature of cathode ray tubes(e) Chadwick
______6.Discovered Radium and Polonium(f) Dalton
______7.Discovered neutron(g) Democritus
______8.Charge to mass ratio of electron(h) Einstein
______9.Charge on the electron(i) Millikan
______10.Discovered radioactivity(j) Moseley
______11.First modern atomic theory(k) Planck
______12.Coined the word “atom”(l) Aristotle
______13.Law of definite composition(m) J. J. Thomson
______14.Law of conservation of mass(n) Lavoisier
______15.Plum pudding model of the atom(o) Gay Lussac
______16.Law of multiple proportions(p) Madam Curie
______17.Discovered electron(q) Proust
______18.Claimed that there are only four elements