Download - How Atoms Differ
How Atoms DifferMr. E Chemistry
Atomic Number = number of protons in the nucleus of an atom
- It really is the identity of the element. What did you discover yesterday when you changes the amount of protons in an atom?
- The atomic number identifies the element.
C
The # of electrons equals the number of protons in an atom.
If the number of protons does not equal the number of electrons we call it an ion.
Not all atoms of an element are identical. The different versions of an element are called isotopes.
6
Isotope = atoms of the same element with different numbers of neutrons
Ex: Carbon
~95%
C12
6BUT
~5%
C14
6
Protons =
Neutrons =
Protons =
Neutrons =
Mass Number = # of protons + # of neutrons in a single atom
- Different isotopes have different mass numbers
Ex:
K19
39Mass Number
Atomic Number
Protons =
Neutrons =
Mass Number =
- NOT on the periodic table!
Atomic Mass Unit (amu) = defined as 1/12 the mass of a carbon-12 atom
Composed of 2 particles:
1) Proton = positive charge
- mass of 1.673 x 10-24 g = 1 amu (atomic mass unit)
2)Neutron = neutral, no charge
- 1 amu
Average Atomic Mass (or Atomic Mass) = weighted average of all the isotopes of an element
How to calculate it:
Chlorine-35Chlorine-37
Atomic Mass = 34.969 amu Atomic Mass = 36.966 amu75.770% abundance 24.230% abundance
The average atomic mass of chlorine is closer to the mass of chlorine-35 because chlorine-35 is much more abundant in nature.
% Abundance Equation
Electrons = negatively charged particle
- mass = amu … basically no mass!
1
1678
- Charge = # of protons - # of electrons
Ex:
Li3
7Mass Number
Atomic Number
Charge
If there is nothing in the charge position, the atom has 0 charge = neutral!
Protons =
Neutrons =
Electrons=
Ex:
Mg12
24 +2 Protons =
Neutrons =
Electrons=
Cl17
36 -1 Protons =
Neutrons =
Electrons=
Ex:
Na24 Protons =
Neutrons =
Electrons= 10
SProtons =
Neutrons = 16
Electrons= 18