# Ch 4 atoms and isotopes guided read

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Ch 4 atoms and isotopes
Name_________________________ per___________
Section 4.2
1. The three subatomic particles are ________________, _______________ and ______________
2. Neutrons are neutral. Electrons have a ______________________charge so are abbreviated, e-.
Protons have a __________________ charge so are abbreviated, p+.
3. The mass of a proton is equal to the mass of a (n) ________________________. Both these
subatomic particles have a mass of 1 amu. The subatomic particle, __________________, have
so little mass we say their relative mass is zero. The only subatomic particle not in the nucleus is
the __________________.
4. Section 4.3 the atomic mass is always equal to the number of __________________. The
number of protons in an element, give the element its identity. For example, hydrogen always
has 1 proton, lithium has ______________p, and nitrogen has ___________ p.
5. The mass number of an atom is equal to the sum of the number of _________________ and the
number of _____________________. Since helium has 2 n and 2p, its mass would be 4amu. If
an element has 4n and 5p, its atomic mass would be ________________. Since this atom has 5p
the name of this element would be ______________________.
6. To find the number of neutrons, find the difference between the mass number and the atomic
number (or protons). In neutral atoms the number of protons = the number or ____________
7. Using the lithium example, finish the chart below. Assume atoms are neutral.
Name
lithium
calcium
Symbol
Li
Atomic #
3
3
protons
3
20
17
3
electrons
3
20
neutrons
4
21
Mass #
7
36
3
15
8.
31
Notice in the table above, the element lithium appears twice. The atomic number is the same
but the number of _________ and therefore the mass is different in isotopes. There are two
ways to indicate isotopes.
Type 1: name-mass number
Type 2:
mass
symbol
protons
ex: lithium-7
ex: 7 Li
3
On the back: page 119 # 25,28,30,32
ex: carbon -12
ex:
12
6
C
ex: carbon-13
ex:
13
C
6