1. 5

2. Structure of the Atom Atomic number = number of protons in the nucleus
and, in a neutral (+ = -) atom,
the number of electrons outside it
Atomic mass = total mass of protons + neutrons.
It is always a whole number.
Atomic mass – Atomic number =
(protons + neutrons) – (protons) = number of neutrons

3. How many of each “sub-atomic part” (p, n, e-) are in these atoms?
Fluorine (F) Atomic number = 9 Atomic mass = 19 Copper (Cu) Atomic number = 29 Atomic mass = 64

4. How many of each “sub-atomic part” (p, n, e-) are in these atoms?
Fluorine (F) Atomic number = 9 = 9 p (+) = 9 e-Atomic mass = 19 (p + n) Atomic number = 9 = 9 p 10 n

5. How many of each “sub-atomic part” (p, n, e-) are in these atoms?
Copper (Cu) Atomic number = 29 = 29 p (+) = 29 e-Atomic mass = 64 (p + n) Atomic number = 29 = 29 p 35 n

6. Isotope Notation Mg Symbol Written form: Magnesium - 25
Isotope Notation shows the symbol of the element with the atomic mass and atomic number on the left, with the atomic mass above (superscript) and the atomic number below(subscript) .
Atomic Mass “Symbolic Form”
Mg Symbol
Atomic Number
Written form: Magnesium - 25

7. Atomic Structure using Isotope Notation
Atomic Mass Mg Symbol
Atomic Number
Number of protons = Atomic Number = 12
Number of electrons = number of protons = 12
Number of neutrons = Atomic Mass (p + n) 25
– Atomic Number (p) – = 13 n

8. Practice 17 17 17 17 18 20 = Protons = = Electrons = = Neutrons =
Cl Cl
= Protons =
= Electrons =
= Neutrons = 17 17 17 17 18 20
These are two different isotopes of Chlorine:
Chlorine-35 and Chlorine-37
They have the same atomic number (same number of p)
but different masses (different number of n)

9. Tl Tl 204 205 81 81 = Protons = = Electrons = = Neutrons = 81 81 81 81
Tl Tl
= Protons =
= Electrons =
= Neutrons = 81 81 81 81
123
124
These are two different isotopes of Thallium:
Thallium -204 and Thallium -205
They have the same atomic number (same number of p)
but different masses (different number of n)

10. Complete the following sentences:
How Atoms Differ pg 3
Complete the following sentences:
The number of ___________ in an atom is
referred to as its atomic number.
The periodic table is arranged by increasing
______ ________.
Atomic number is equal to the number of
__________ in an atom.
The number of _________ in an atom identifies
it as an atom of a particular element.
The number of __________ plus the number of
protons is equal to the atomic mass of an element.
protons
atomic number
protons
protons
neutrons

11. Use the figures below to answer the following questions:
Osmium 76 Os
190.23
Niobium 41 Nb
92.906 76
6. What is the atomic number of osmium? __________________
7. What is the chemical symbol for niobium? ________________
8. What is the atomic mass of osmium? ____________________
9. What units is the atomic mass reported in? _______________
10. How many protons and electrons does an osmium atom have?
A niobium atom? ___________ ___________ Nb
190.23
amu 41 76

12. Mg Ne 24 12 22 10 atomic mass atomic number
Label the mass number and the atomic number on the following isotope notation:
atomic mass 24 Mg 12
_______________
atomic number
_______________
Write each isotope below in symbolic notation.
Use the periodic table to determine the atomic
number of each isotope.
13. Neon-22 22 Ne 10

13. Write each isotope below in symbolic notation.
Use the periodic table to determine the atomic
number of each isotope.
Helium-4
Cesium-133
Uranium-234
17.Cesium-132 4 He 2
133 Cs 55
132 Cs 55
< Isotopes of the same element >
234 U 92