Name ___________________________________ Date ____________
Period___
Guided Nuclear Symbols
Directions: Please consult your book (pp. 75-77) in order to fill in the blanks and answer the
questions.
The __________________ (1) number of an element is the number of protons in the nucleus of
each atom of that element.
This number is found on the periodic table above each element’s symbol.
Example:
3
Li
Isotopes are atoms of the same element that have different _____________________(2).
The isotopes of a particular element all have the same number of ________________(3)
and _________________(4) but different numbers of __________________(5).
The __________________ (6) number of an element is the total number of protons AND
neutrons in the nucleus in the nucleus of an isotope.
Chemists use hyphen notation in order to specify isotopes. Hyphen notation is simply written
as: element name – mass number. For example, carbon – 14.
Chemists use nuclear symbols in order to specify isotopes. A generic nuclear symbol is shown
below.
Mass number
Atomic number
𝐴
𝑍𝑋
Atomic symbol
The nuclear symbol helps us calculate how many protons, neutrons, and electrons that an
isotope has. Take a look at the example below for hydrogen – 3.
3
1𝐻
Element: hydrogen, # of protons = 1, # of electrons = 1, # of neutorns = 2
(7) How do you find the number of protons and electrons in an isotope?
(8) How do you find the number of neutrons in an isotope?
(9) What is an ion? (Look up the definition in your glossery).
An ion is formed when an atom gains or loses electrons.
An electron has a ___________________ [positive or negative] (10) charge.
If an atom gains an electron there is __________________ [more or less] (11)
negative charge in the atom and it is called an anion.
If an atom loses an electron there is __________________ [more or less] (12)
negative charge in the atom and it is called a cation.
IMPORTANT NOTE: The electron is the ONLY subatomic particle involved in the
formation of ions. Protons are NOT involved.
We can also have nuclear symbols for ions. Take a look at the nuclear symbol for a
sodium ion (cation).
Charge
Mass number
23
+
Atomic number
11𝑁𝑎
Element: sodium, # of protons = 11, # of electrons = 10, # of neutrons = 12,
charge = +1
(13) How do you find the number of electrons in a cation?
Take a look at the nuclear symbol for a bromine ion (anion).
81
−
35𝐵𝑟
Element: bromine, # of protons = 35, # of electrons = 36, # of neutrons = 46
(14) How do you find the number of electrons in an anion?
Fill out the table below.
Nuclear Symbol
Charge
236
0
92𝑈
40
2+
+2
20𝐶𝑎
14 3−
-3
7𝑁
# of protons
# of electrons
# of neutrons