Download Section 3.2 Guided Notes

Section 3.2: “Structure of Atoms”
1. Scientists discovered that atoms _______ be broken down into smaller parts called
_____________ ____________.
a. The 3 types of subatomic particles that are most important in chemistry are:
b. _______________
c. _______________
d. _______________
2. ______________ Were Discovered by Using Cathode Rays
a. J.J. Thomson was studying _________________, not atomic structure, when he
discovered ________________.
b. He pumped ________ out of a sealed glass tube and attached __________ to
each end.
c. Anode: ___________________________
d. Cathode: __________________________
e. A glowing beam came out of the ________________.
f. He called the beam a “____________ ________”.
g. The glass tube is known as a _____________ ________ _________ (CRT).
3. An ______________ Has a _____________Charge
a. Thomson reasoned that the ray was negatively charged since it was coming from
the ____________.
b. He placed a ___________ by the tube and saw the ray _______________.
c. He placed a small paddle wheel in the __________ of the ray and saw the wheel
____________, showing that something with __________ was hitting the wheel.
d. Thomson concluded that the ray was made of negatively charged _____________
that have ____________.
e. Thomson called these particles _____________.
4. Electron: a ______________ particle that has a _____________ charge.
5. Scientists began to look for more subatomic particles for 2 reasons:
a. Since ______________ have a negative charge but atoms have ______ charge,
there must be other subatomic particles that have a _____________ charge to
___________ out the electron’s negative charge.
b. The __________ of an atom is much larger than the mass of an ____________,
so there must be other subatomic particles in the atom.
6. J.J. Thomson proposed that ______________ were embedded in a ___________ of
positive charge.
a. Thomson called this model the “ ___________ ______________ _________”
7. Rutherford Discovered the ________________
a. Rutherford directed a beam of _______________ charged alpha particles at a
thin foil of _________.
b. Most of the particles passed straight _________ the foil, but a few were
______________, some even ____________________.
c. Only a very concentrated ___________ charge in a tiny space within the gold
atom could possibly repel the fast-moving alpha particles enough to ___________
their direction.
d. The ________ of this tiny, positively charged region must be _________ than
the mass of the alpha particle or it would simply have been knocked out of the way.
8. Rutherford hypothesized that __________ are mostly __________ space except for
the dense center, or ___________.
a. Nucleus: an atom’s central region, which is made up of ___________ and
_____________.
b. The nucleus has all of the ___________ charge, nearly all of the __________,
but only a very small fraction of the ____________ of the atom.
9. _____________ are in the ______________.
a. The positively charged particles in the __________ were called ___________.
b. Proton: a subatomic particle that has a _____________ charge and that is found
in the _____________ of an atom; the number of protons of the nucleus is the
___________ ____________, which determines the ____________ of an
element.
c. A proton’s __________ is about 2,000 times that of an _____________.
10. Because an atom’s mass is _____________ than the sum of its _____________ and
____________, scientists began looking for another subatomic particle…
11. James Chadwick Discovered _____________
a. Neutron: a subatomic particle that has _______ charge and that is found in the
____________ of an atom.
b. A neutron has about the same mass as a ___________.
12. Coulomb’s Law the ___________ two charges are, the ___________ the force
between them. (Think magnets)
a. Also, the ________________ the two charges are, the _______________ the
force between them.
13. Why is the ____________ Stable?
a. If the nucleus is made up of positively charged ___________ and __________
with no charge, why doesn’t the ___________ of repulsion push the protons apart
and make the nucleus unstable? _______________________________
14. A fundamental force of nature, the ____________ force, overcomes the repulsive
forces between positively charged __________ in the nucleus.
a. All atoms that have more than 1 ____________ also have __________ to help
______________ the nucleus.
15. Atomic Number is the Number of ________________ in the _____________.
a. Atomic Number: the number of ______________ in the nucleus of an
___________; the atomic number is the ___________ for all ____________ of
an _______________.
b. No two ______________ can have the same _____________ _____________.
16. The Atomic Number Also Tells the Number of ________________.
a. For atom to be electrically ______________, the number of positively charged
__________ must __________ the number of negatively charged
____________.
b. If you know the number of ___________ in an atom, you automatically know the
number of ____________ too!
17. Mass Number: the sum of the numbers of _____________ and _____________ of
the ______________ of an atom.
a. Mass Number = Number of Protons + Number of Neutrons
b. Unlike the ____________ number, the ___________ number can vary between
atoms of a single _____________.
18. Sample Problem A, pg. 86
How many protons, electrons, and neutrons are there in an atom of copper whose atomic
number is 29 and whose mass number is 64?
19. Practice Problem #3, pg. 86
Calculate the mass number for an atom that has 45 neutrons and 35 electrons.
20. Atomic Structures Can be Represented by _____________. (nuclear symbols)
a. Each _____________ has a name and ____________ that is listed in the
periodic table of elements.
b. Sometimes, _____________ numbers and _____________ numbers are written
with an element’s symbol.
Atomic Number: _________ number
Mass Number: has a _____________ point
21. The atomic number always appears on the ____________ _________ side of the
element’s symbol:
Examples:
a.
Mass numbers are written on the ____________ __________ side of the
symbol:
Examples:
Remember: Mass Number = number of protons + number of neutrons
22. _______________ of an Element Have the Same ____________
____________
a. All atoms of an ____________ have the same atomic number and the same
number of ______________.
b. However, atoms of the same element do not necessarily have the same number of
_____________.
c. Isotope: an atom that has the same number of _____________ (atomic number)
as other atoms of the same element, but has a different number of
______________ (atomic mass).
23. Two Ways of Identifying Isotopes
a. Write the _______ number with a hyphen after the symbol for the element:
He-3
This is a ______________ atom with a mass number of _________.
b. Write the nuclear symbol for the isotope:
2
3
He
This is also a ____________ atom with a mass number of _______.
*Remember: all ____________ of an element have the same ___________
__________ and the same number of ______________*
24. Sample Problem B, Pg. 89
Calculate the number of protons, electrons, and neutrons in oxygen-17 and oxygen-18.
(17 and 18 are the mass numbers)