Download Finding the Amounts of Subatomic Particles

Subatomic Particles
An atom is the smallest part of an
element that retains the same chemical
properties as the element.
 The nucleus is the central part of an
atom. It is made up of protons and
neutrons and contains most of the atom’s
mass.
 The nucleus was discovered by Ernest
Rutherford in 1911.

Atoms

Protons (p+)
◦ Positively charged particles found in nucleus.
◦ Mass of 1 atomic mass unit (AMU).
◦ Discovered by Ernest Rutherford in 1911.

Neutrons (n0)
◦ Neutral particles found in nucleus.
◦ Mass of 1 atomic mass unit (AMU).
◦ Discovered by James Chadwick in 1932.

Electrons (e-)
◦ Negative particles found in nucleus.
◦ Negligible mass.
◦ Discovered by J.J. Thomson in 1897.
Subatomic Particles
The number of protons in an atom
 Can be found by looking at the top of each
box on the periodic table


In a neutral atom, the number of electrons
is the same as the number of protons
Atomic Number

The number of protons and neutrons added
together.
Usually seen after the element name or
symbol (carbon – 13). Mass number is NOT
found on the periodic table.

Mass Number = p+

How would you find the neutrons if you knew
the protons and mass number?

+
no
◦ Neutrons = mass number – protons
Mass Number

How many protons, neutrons, and
electrons are in a neutral atom of:
fluorine – 20.
◦ Protons =
◦ Neutrons =
◦ Electrons =

9 (from periodic table)
11 (20 – 9)
9 (electrons = protons)
Isotopes of the same elements have:
◦ Same number of protons & electrons and
atomic number.
◦ Different number of neutrons and therefore a
different mass number.
Example

Atoms of the SAME element, with different
numbers of neutrons

Example:
◦ Copper – 63
 (29 p+, 34 no, 29 e-)
◦ Copper – 65
 (29 p+, 36 no, 29 e-)
Isotopes

𝑴𝒂𝒔𝒔 𝑵𝒖𝒎𝒃𝒆𝒓
X
𝑨𝒕𝒐𝒎𝒊𝒄 𝑵𝒖𝒎𝒃𝒆𝒓

Copper-63
◦

𝟔𝟑
Cu
𝟐𝟗
Copper-65
◦
𝟔𝟓
Cu
𝟐𝟗
Isotope Symbols