Download History of Atomic Theory Worksheet

Development of Atomic Theory
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
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
cannot be created or destroyed. Then
(4) proposed, in his law of
_____(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).
1. __________________
2. __________________
3. __________________
4. __________________
5. __________________
6. __________________
7. __________________
8. __________________
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 goldfoil experiment.
9. __________________
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)
14. _________________
10. _________________
11. _________________
12. _________________
13. _________________
15. _________________
16. _________________
17. _________________
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 I
Column II
______ 1.
Determined that most of the atom is empty
(a) Rutherford
______ 2.
(b) Becquerel
______ 3.
Worked extensively with cathode ray tubes
to decipher the structure of the atom
Planetary model of the atom
______ 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”
______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)
______ 18.
Claimed that there are only four elements
(c) Bohr
(l) Aristotle
Proust