Explaining the Periodic Table (6.7)
• If elements are the building blocks of all other matter, what
are they made of?
• There are three particles that make up an atom or element:
• protons
• electrons
• neutrons
• These are called subatomic particles because they are
smaller or below an atom.
PROTONS are located in the nucleus and have a positive charge.
NEUTRONS are also located in the nucleus and have no charge.
ELECTRONS are located in orbits around the nucleus. They have a
negative charge.
Explaining the Periodic Table (6.7)
How many ELECTRONS, PROTONS and NEUTRONS are
in an atom?
atomic number
element symbol
6
C
atomic mass
(mass number)
carbon
12.01
element name
Atomic Number
atomic number
• atomic number = # of protons
6
C
carbon
12.01
• each element has a unique atomic number
• each element is identified by its atomic number and
number of protons
• (ex. the element carbon, and only carbon, has the atomic
number of 6)
• In a neutral atom, the number of positives must equal the
number of negatives.
• This means the # of electrons = # of protons
6
Atomic mass
(mass number)
atomic mass
(mass number)
C
carbon
12.01
• atoms of an element may have different masses
because they have different numbers of neutrons –
these are called isotopes
• round mass to a whole number
mass number = sum of protons + neutrons
From the atomic number and mass number of an atom, we
can determine the number of protons, electrons, and
neutrons in an atom.
# protons = atomic number
# electrons = # protons (for neutral atoms only)
# neutrons = mass number – atomic number
Ex)
Determine the number of protons, electrons and neutrons
in the following atoms:
a) Fluorine
b) Bromine
c) Sodium
35 protons
____
11 protons
____
____ electrons
35 electrons
____
____ electrons
10
____ neutrons
45
____ neutrons
12
____ neutrons
9 protons
____
9
11
Bohr-Rutherford diagrams are drawings of atoms that show
the number of protons and electrons in the nucleus and the
number of electrons in each energy level (orbit).
Ex)
1st orbit can hold 2 electrons
The 2nd and 3rd orbits can hold 8 electrons
Let’s try drawing Bohr-Rutherford Models:
1 H
Hydrogen
1
0
1
5 B
Boron
2-3
5
6
10 Ne
Neon
2-8
10
10
13 Al
Aluminum
2-8-3
13
14
16 S
Sulphur
2-8-6
16
16
19 K
Potassium
2-8-8-1
19
20