Development of Atomictheory

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