Download Notes on Atomic Structure Structure of Atoms Atoms are composed

Notes on Atomic Structure
Structure of Atoms
Atoms are composed of Protons, Neutrons, and Electrons.
The protons and neutrons are found in the nucleus (the center) of
the atom.
The electrons are found in the electron cloud surrounding the
nucleus.
Protons have a POSITIVE (+) electrical charge.
Neutrons have No charge. They are Neutral.
Electrons have a NEGATIVE (-) electrical charge.
Element Key
The periodic table is a list of the elements that make up matter. It is organized by increasing atomic number.
The Atomic Number shows the number of protons in the nucleus of an atom. It identifies the type of
atom/element.
The atomic number also equals the number of electrons whenever the atom is neutral.
To find the number of neutrons, subtract the number of protons from the mass number.
The mass number is the number of protons plus the number of neutrons.
The mass number can be found by rounding the average atomic mass of the element to the nearest whole
number (The average atomic mass can be found in the periodic table).
Example: Phosphorus has an average atomic mass of 30.974
The mass number would be 31.
Now, subtract the number of protons from the mass number to get the number of neutrons: 31-15= 16
So, Phosphorus has: 15 protons
15 electrons
16 neutrons
For any element, the number of neutrons in the nucleus can vary from atom to atom.
Atoms of the same element with different number of neutrons are called isotopes of that element.
Isotopes of an element have different mass but essentially the same chemical properties.