1. What would happen if the number of protons were to change in an atom?
Here are three isotopes of an element: 12 C 6, 13 C 6, 14 C 6
a. The element is: __________________
b. The number 6 refers to the ____
c. The numbers 12, 13, and 14 refer to the _____
d. How many protons and neutrons are in the first isotope? _________________
e. How many protons and neutrons are in the second isotope? _________________
f. How many protons and neutrons are in the third isotope? _________________

2. Variations on the Atom Dr. M. Hazlett Mandeville High School
Isotopes and Ions
Variations on the Atom
Dr. M. Hazlett
Mandeville High School

3. 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)

4. 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

5. 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
These can be looked up in the CRC (the Chemistry/Physics Data Bible) or on the internet
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!

6. The Carbon Isotope

7. 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

8. 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

9. 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 this like: 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

10. Group Names to Know Group 1 = Alkali Metals Group 2 = Alkaline Earth Metals Groups 3 to 12 = Transition Metals Group 16 = Chalcogens Group 17 = Halogens Group 18 = Noble Gases