1.2 Isotopes

1.2 Isotopes

These images represent 2 isotopes of carbon

The red circles are protons

The grey circles are neutrons

How would you name these to clearly indicate which element they are and what their masses are?

Open Ended

How would you name these atoms?

(whatever seems logical to you)

(remember, these are 2 different atoms and the red spheres are protons, the grey spheres are neutrons

Naming Isotopes:

"element-mass #"

(or as "chemical symbol-mass #")

• Carbon-12

• C-12

• Carbon-14

• C-14

Definition of isotopes

• atoms that have the same number of protons, but different numbers of neutrons

• Example: C-12 has 6 protons and 6 neutrons ; C-14 has 6 protons and 8 neutrons. Both are carbon and act chemically the same (same chemical properties because neutrons do not affect charge of the nucleus)

• C-12 has a nuclear charge of 6+

• C-14 has a nuclear charge of 6+

• Isotopes differ in mass, but not nuclear charge (same Atomic Number)

Multiple Select

Select the 2 nuclei that represent a pair of isotopes?

• 7 protons & 8 neutrons

• 8 protons & 7 neutrons

• 7 protons & 7 neutrons

• 9 protons & 8 neutrons

Mass Number = protons + neutrons

• Can be rearranged based on the question...

• protons = Mass Number - neutrons

• neutrons = Mass Number - protons

Multiple Choice

Since... Mass Number = protons + neutrons

How many neutrons are in an atom of Magnesium-25?

(key info: The atomic number of magnesium is 12)

• 12

• 13

• 25

• 37

Isotopes

• atoms with same # protons , different # of neutrons

• Atoms of the same element can have slightly different masses, but behave chemically the same way.

• Named as "element-mass #" (Ex: nitrogen-15)

• Shorthand is "chemical symbol-mass #" (Ex: N-15)

Multiple Choice

In the isotope name Lithium-7 , the 7 represents

• The atomic number

• the mass number