Download Atomic Theory

The Elements.
How do the parts of an atom
influence the elements?
Recap

Atoms have a positively charged nucleus
that contains both protons and neutrons.

Electrons orbit around the nucleus in a
“cloud”
What determines an Element?

The number of protons inside an atom
determine which element it is.

1 proton means Hydrogen.

2 protons means Helium.

What element has 15 protons?
Atomic Charge
Protons are +
 Electrons are –
 Neutrons are neutral


An atom prefers to be neutral thus having
a net charge of zero.
Atomic Number

The number of protons in an atom.
Atomic Number
8
Atomic Number
O
16
Oxygen has an atomic number of 8. What
does that tell me about the number of
protons it has?
Atomic Mass (Mass Number)

The atomic mass is the total number of
proton plus total number of neutrons
inside an atom.
Protons + Neutrons = Atomic Mass
Mass Number
8
O
16
Mass Number
How do we find the number of
neutrons?
Number of neutrons = Mass number –
Atomic number
OR
 Number of neutrons = (# neutrons + #
protons) – (# protons)


So….how many neutrons does
Chromium (Cr) have?
How do we determine the number
of electrons?

Number of electrons = number of
protons
Atomic Mass

What is the atomic number, atomic mass,
number of protons, number of neutrons,
and number of electrons of the following
element?
30
Zn
65.39
Isotopes

An atom with the same number of
protons and a different number of
neutrons.