1. Atomic Structure & Notation
Atoms
Protons
Neutrons
Electrons
Atomic Number
Mass Number
Atomic Symbols
Calculations

2. ATOMS Atoms are the building blocks of all matter.
An atom is made up of smaller bits called subatomic particles which include...
Name
Charge
Position
Mass
Protons +
Nucleus 1
Electrons -
Outside
Neutrons
neutral
Nucleus 1

3. Atoms – Bill Nye
Complete the Bill Nye Atoms Worksheet

4. What is the structure of an atom?
Nucleus
Where the positive charge resides
Later called the proton
Later evidence showed the existence of a neutral particle (no charge)
Later called the neutron

5. What is the structure of an atom?
Proton (p+)
Has a positive (+) charge
Has a relative mass of 1
Determines the atomic number
Found inside the nucleus

6. What is the structure of an atom?
Neutron (n0)
Has no (0) charge
Has a relative mass of 1
Determines the isotope
Isotopes are two of the same element with different masses
Found inside the nucleus

7. What is the structure of an atom?
Electron (e-)
Has a negative (-) charge
Has a relative mass of 0 (zero)
Determines the ion (more later)
Found outside the nucleus

8. Atomic Number # protons = # electrons
Each element is different because they contain different numbers of PROTONS
The “atomic number” of an element is the number of protons in the nucleus
# protons = # electrons

9. Atomic Number
Atomic number of an element is the number of protons in the nucleus of each atom of that element.
Element
Atomic #
# of protons
Carbon 6
Phosphorus 15
Gold 79

10. Mass Number
Atomic Mass (Mass Number) is the number of protons and neutrons in the nucleus of an atom:
Mass # = p+ + n0
Atom p+ n0 e-
Mass #
Oxygen - 8 - 33 42
- 31 15 16 8 8 16
Arsenic 75 33 75
Phosphorus 16 15 31

11. Atomic Notation
Contains the symbol of the element, the mass number and the atomic number.
Superscript →
Atomic number X
Symbol
Mass number
Subscript →

12. Atomic Notation Example2
Atomic number He
the number of protons in an atom
Symbol 4
Atomic mass
the number of protons and neutrons in an atom

13. What is a chemical symbol?
The chemical symbol tells us what atom it is
It’s a short form (C = Carbon)
sometimes it’s the Latin short form (Au = Gold)
Always a CAPITAL LETTER, sometimes followed by one or more lower case letters
Ex: Oxygen O, Nitrogen N, Sodium Na
*Cobalt – Co *Carbon Monoxide – CO
(Co is an element, CO is a compound)

14. Atomic Number
Symbol
Atomic Mass

15. Recall - How are P, N, e- related?
atomic number = # protons
# protons = # electrons in a neutral atom
# protons + # neutrons = atomic mass
# neutrons = atomic mass - # protons
# protons = atomic mass - # neutrons

16. Example 1
How many protons, neutrons and electrons are found in an atom of Cs?
Atomic number = protons
There are 55 protons
Mass number = sum of protons and neutrons
Therefore, # Neutrons = Mass Number - # Protons
# Neutrons = 133 – 55
# Neutrons = 78 55 Cs
133

17. H 1 1 Hydrogen Protons: 1 Neutrons: 0 Electrons: 1
# protons + # neutrons = atomic mass

18. Na 11 23 Sodium Protons: 11 Neutrons: 12 Electrons: 11
# protons + # neutrons = atomic mass

19. Example 2
If an element has an atomic number of 34 and a mass number of 78, what is the:
number of protons
number of neutrons
number of electrons
complete symbol
= 34  # p+ = Atomic Number
= 44 # n0= Atomic Mass - # p
= 34  # e- = # p+
34  Atomic #
= Se  Symbol
78  Atomic Mass

20. Example 3 If an element has 91 protons and 140 neutrons what is the
Atomic number
Mass number
number of electrons
complete symbol
= 91  # p+ = Atomic Number
= 231
Atomic Mass = # n0 + # p
= 91  # e- = # p+
91  Atomic #
= Pa  Symbol
231  Atomic Mass