Name ______________________________ Date ______________________ Section ____________
Introduction to Atoms
Around 440 B.C. a Greek philosopher named Democritus believed that matter was made up
of tiny pieces that he called “atomos”, which is Greek for “uncuttable.” We now identify
these small particles as atoms. Atoms are the building blocks of all matter. In 1802 British
schoolteacher John Dalton proposed a theory about atoms. He believed that atoms were
like little marbles. In 1897 J.J. Thompson discovered electrons. He proposed
that atoms were like raisin buns, with the dough being a positively charged
material, with the raisins scattered throughout like negatively charged electrons.
In 1911 Ernest Rutherford conducted experiments where he shot radioactive material
at a piece of gold foil. He found that atoms were mostly empty space, but concluded
that they had a nucleus with positively charged protons inside. In 1913, Niels Bohr
improved on Rutherford’s model and found that electrons were arranged in specific
orbits around the nucleus. In 1932 James Chadwick worked with Rutherford to
discover neutrons, particles with no charge. The current model of the atom
contains protons and neutrons in the nucleus of the atom, with electrons
forming a negatively charged cloud around it.
Label It
Correctly label the parts of the atom using the words and phrases below.
Electron
Electron cloud
Proton
(+ charge)
Electron shell
(- charge)
Neutron
Nucleus
(0 charge)
5. _______________
6. _______________
1. _______________
7. _______________
2. _______________
3. _______________
4. _______________
8. _______________
9. _______________
©2017 Adventures in Science
Who Did It?
Dalton’s Atomic Theory
•Atoms can’t be broken into
smaller pieces.
Correctly match the person to their accomplishment. Each name may be
used more than once.
Bohr
Chadwick
Dalton
Democritus
Rutherford
10.
Discovered the nucleus _______________
11.
Responsible for naming the atom _______________
12.
Created an atomic theory _______________
•In any element, all the ele
ments
are exactly alike.
Thompson
•Atoms of different elements
are
different.
•Atoms of two or more ele
ments
can combine to form compou
nds.
•Atoms of each element hav
ea
unique mass.
13. Discovered the proton _______________
14.
•The masses of the elements
in a
compound are always in a
constant
ratio.
Discovered atoms were mostly empty space _______________
15. Discovered the electron _______________
16.
Worked with Rutherford to discover the neutron _______________
17. Concluded that electrons move in orbitals _______________
18.
Stated that atoms could combine to form elements _______________
19.
First known person to believe that matter was made up of tiny indivisible pieces _____________
20.
Proposed (but didn’t prove) the existence of a positively charged particle _______________
Identify It
Atoms can be identified by counting the number of protons. Using the The Periodic Table of Elements to
help you, identify each of the atoms below.
21. ______________
22. ______________
23. ______________
Dalton’s Atomic Theory: True or False?
24. All the atoms of any one type of element (like silver) are exactly alike. _________
25. Atoms can’t be broken into smaller pieces and still retain the properties of that element.. _________
©2017 Adventures in Science
Answers
Name ______________________________
Date ______________________ Section ____________
Introduction to Atoms
Around 440 B.C. a Greek philosopher named Democritus believed that matter was made up
of tiny pieces that he called “atomos”, which is Greek for “uncuttable.” We now identify
these small particles as atoms. Atoms are the building blocks of all matter. In 1802 British
schoolteacher John Dalton proposed a theory about atoms. He believed that atoms were
like little marbles. In 1897 J.J. Thompson discovered electrons. He proposed
that atoms were like raisin buns, with the dough being a positively charged
material, with the raisins scattered throughout like negatively charged electrons.
In 1911 Ernest Rutherford conducted experiments where he shot radioactive material
at a piece of gold foil. He found that atoms were mostly empty space, but concluded
that they had a nucleus with positively charged protons inside. In 1913, Niels Bohr
improved on Rutherford’s model and found that electrons were arranged in specific
orbits around the nucleus. In 1932 James Chadwick worked with Rutherford to
discover neutrons, particles with no charge. The current model of the atom
contains protons and neutrons in the nucleus of the atom, with electrons
forming a negatively charged cloud around it.
Label It
Correctly label the parts of the atom using the words and phrases below.
Electron
Electron cloud
Proton
(+ charge)
Electron shell
(- charge)
Neutron
Nucleus
(0 charge)
neutron
5. _______________
(0 charge)
6. _______________
electron cloud
1. _______________
nucleus
7. _______________
proton
2. _______________
(+ charge)
3. _______________
4. _______________
electron shell
electron
8. _______________
9. _______________
(- charge)
©2017 Adventures in Science
Who Did It?
Dalton’s Atomic Theory
•Atoms can’t be broken into
smaller pieces.
Correctly match the person to their accomplishment. Each name may be
used more than once.
Bohr
Chadwick
Dalton
Democritus
Rutherford
10.
Rutherford
Discovered the nucleus _______________
11.
Democritus
Responsible for naming the atom _______________
12.
Dalton
Created an atomic theory _______________
•In any element, all the ele
ments
are exactly alike.
Thompson
•Atoms of different elements
are
different.
•Atoms of two or more ele
ments
can combine to form compou
nds.
•Atoms of each element hav
ea
unique mass.
13. Discovered the proton _______________
Rutherford
Rutherford
Discovered atoms were mostly empty space _______________
Thompson
15. Discovered the electron _______________
Chadwick
16. Worked with Rutherford to discover the neutron _______________
14.
•The masses of the elements
in a
compound are always in a
constant
ratio.
Bohr
17. Concluded that electrons move in orbitals _______________
18.
Dalton
Stated that atoms could combine to form elements _______________
19.
Democritus
First known person to believe that matter was made up of tiny indivisible pieces _____________
Thompson
Proposed (but didn’t prove) the existence of a positively charged particle _______________
20.
Identify It
Atoms can be identified by counting the number of protons. Using the The Periodic Table of Elements to
help you, identify each of the atoms below.
Neon
21. ______________
Oxygen
22. ______________
Aluminum
23. ______________
Dalton’s Atomic Theory: True or False?
True
24. All the atoms of any one type of element (like silver) are exactly alike. _________
True
25. Atoms can’t be broken into smaller pieces and still retain the properties of that element.. _________
©2017 Adventures in Science
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