isotope and average atomic mass

Carbon 12

Consider the Atom Carbon, the atomic number tells us the number of protons.

How many protons in Carbon 12?

Ion Notation

• Same as isotope

• includes charge in upper right

• + means LESS ELECTRONS than PROTONS

• (-) means MORE ELECTRONS than PROTONS

Isotopes

• atoms with the SAME number of PROTONS but DIFFERENT number of NEUTRONS

Ions

• Ion means charged atom

• To be charged it needs more or less electrons than protons

• more electrons = NEGATIVE

• less electrons = POSITIVE

Average Atomic Mass

• DIFFERENT than Mass Number

• Average of all of the isotopes of an atom found in nature.

How they get that number

• % abundance of that isotope x actual mass of that isotope

• add together

• divide by 100 (if you didn't put into percentage first)

Multiple Choice

Look carefully at the diagram. The atoms that are isotopes of the same element are:

• A & D

• D & X

• X & Y

• Y & A

Multiple Choice

The correct way of showing the isotope of nitrogen with 7 protons and 8 neutrons is:

• ⁸₇N

• ⁷₈N

• ¹⁵₈N

• ⁸₁₅N

Multiple Choice

How many protons?

• 36

• 17

• 18

• 19

Multiple Choice

How many neutrons?

• 9

• 4

• 5

• 2

Multiple Choice

What are AMU's

• Atomic Mass University

• Atomic Mass Units

• Atoms mean unity

• All Mass United

Multiple Choice

24.1% of all the isotopes of a an element have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 27.2% have a mass of 75.20 amu.
What is the average mass of this element?

• 74.92 amu

• 24.97 amu

• 75.01 amu

• 74.51 amu

Multiple Choice

An isotope has three forms.  30% have a mass of 4 amu, 20% have a mass of 5 amu and 50% have a mass of 3 amu.  Average atomic mass will be closest to

• 2 amu

• 3 amu

• 4 amu

• 5 amu