Name
Period
Practice Sheet #9
AtomicStructure and History of Atomic Theory
1. John Dalton did reactions that showed matter must be composed of small indivisible particles (he
said spheres) which he called atoms. He borrowed the name from Greek philosopher Democratis, who first “thought” about building blocks
of matter. Why does Democratis not get credit for discovering the existence of atoms?
2. Briefly explain how....
a. ....J.J. Thompson proved the existence of electrons in atoms:
b. ....Thompson’s experiment improved Dalton’s model of the atom:
c. ....Thompson deduced the existence of a positive component in the
atom:
3. Briefly explain.....
a. ....how Rutherford proved the existence of the nucleus:
b. ....how Rutherford’s experiment improved Thompson’s “Raisin Bun”
model of the atom:
c. ....what information Rutherford got about electrons from his experiment:
4. What additional information did Niels Bohr gain about atoms from his
experiment? Be sure to include a brief description of the experiment:
-----> more
MATCHING (More than one answer possible and answers may be used more than once!)
5. proton
6. nucleus
7. electron
8. neutron
9. electron cloud (orbitals, etc.)
10. atom
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
negative charge
very dense
negligible mass
positive charge
located in the nucleus
no charge
extremely small
mostly empty space
has a mass of 1 amu
located far outside of the nucleus
11. An atom has an atomic number of 7 and a mass number of 15.
• How many protons does this atom have?
• How many electrons does a neutral atom have?
• How much does the nucleus weigh?
• This is an atom of the element
• How many neutrons does this atom have?
• Draw a labeled diagram of this atom, including the protons, neutrons, electrons, nucleus, electron cloud:
12. An atom has a nucleus that weighs 10 amu’s and has 4 electrons.
• What is an amu?
• How many protons does this atom have?
• This is an atom of the element
• What is the atomic number of this element?
• How many neutrons are in the nucleus of this atom?
• What is the atom’s mass number?
• Draw a labeled diagram of this
atom, including the protons,
neutrons, electrons, nucleus,
electron cloud: