1. Isotopes and Ions
Variations on the Atom

2. Isotopes All atoms of an element have the SAME number of protons (p+)
The p+ number is the atomic number (Z)
This is a constant
For example: All Sodium (Na) atoms have 11 p+
If an atom loses a proton, it becomes a different element
If Na loses 1 p+, then it has become Neon (Ne)

3. Z = atomic number = p+
The number of protons identifies the atom and which element it is
In a stable atom:
# p+ = # n0 = # e-
Thus, Na in its stable form has 11 p+; 11 n0; and 11 e-
If it has an unequal number of p+ and n0, then it is called an ISOTOPE

4. For example: H has 3; C has 16; Al has 25
Theoretically – an element can have as many isotopes of itself as it has neutrons, or it can add an unlimited number of n0
For example: H has 3; C has 16; Al has 25
Remember – a change in the number of n0 does not change the element’s atom – only a change in the number of protons can do that!

5. The Carbon Isotope

6. Ions Ions are when an atom has an unequal number of p+ and e-
Remember – a stable atom has a neutral overall charge due its equal number of p+ and e-
When an atom loses or gains an e-, its charge changes accordingly
Loss of e- means a + charge; gaining an e- means a – charge for the atom

7. Losing or Gaining e
If an atom loses an e-, then it has more p+ than e- and it will have an overall positive charge
Different elements’ atoms can lose 1, 2, 3, or even 4 electrons depending on various factors
If an atom has LOST e-, then it is called a CATION or a positive ion
A Cation would be written as Al+ (the one being understood) or Al+3

8. Atoms can also gain electrons
If an atom gains electrons (from 1 up to 4), then it will have more e- than p+ and will end up having an overall negative charge
A negatively charged ion is called an ANION
The element is shown like this: Na- (the 1 is understood) or Na-2
The losing or gaining of electrons determines what type of bonds the atoms will form, and which atoms will bond to others