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Isotopes

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Atomic Number

- Atomic number = number of protons
- Which makes it always a whole number

- Atomic number is always the same for a given element
- Can be found on the periodic table

Isotope

- Atoms of the same element with different number of neutrons
- They have different mass numbers
- They have the same number of protons
- Nuclide
- General name for an isotope of an
atom

- General name for an isotope of an

Mass Number

- Atoms of the same element may have different numbers of neutrons
- Mass number
- Sum of protons + neutrons

- Mass number can not be found on the periodic table
- Not found by rounding atomic mass
- Given through words or symbols

Atomic Mass

- Weighted average of the masses of naturally occurring isotopes of an element
- Can be found on the periodic table
- It is not usually a whole number

Calculating Average Atomic Mass

- Depends on both mass and relative abundance
- How do you find average atomic mass?
- Naturally occuring copper consists of 69.15% copper-63 which has an atomic mass of 62.929601 amu and 30.85% copper-65 which has an atomic mass of 64.927794
- Multiply the atomic mass of each isotope by its relative abundance(expressed as a decimal) and add the results
- 0.6915 x 62.929601 amu + 0.3085 x 64.927794 amu = 63.55 amu

Calculating average atomic mass

- Three isotopes of Argon occur in nature. Calculate the average atomic mass of Argon to decimal places:
Argon-36 (35.97 amu; 0.337%)

Argon-38 (37.96 amu; 0.063%)

Argon-40 (39.96 amu; 99.600%)

Answer: 39.95 amu

Isotopes of Hydrogen

- Protium
- Deuterium
- Tridium

Isotopes of Hydrogen

faculty.weber.edu/bdattilo/shknbk/notes/time.htm

Isotopes

- Hydrogen isotopes are different because most isotopes do not have their own specific name
- They are identified by their mass number

Isotope Stability

- Stable nucleus
- a correct ratio of neutrons and protons should be present in the nucleus.

- Unstable nucleus
- radioactive

- Elements 83-112 radioactive
- Elements 93-112 man-made

1. Sodium-23

2. calcium-40

3. Cu

4. Ag

64

Problems – determine the # of p+, n, and e- in each of these.1. 11 p+, 11 e-, 12 n

2. 20 p+, 20 e-, 20 n

3. 29 p+, 29 e-, 35 n

4. 47 p+, 47 e-, 61 n

29

108

47

Problems – write the nuclear notation and hyphen notation for

- 5. mass number 28, atomic number 14
- 6. 26 protons and 30 neutrons
- 7. 56 electrons and 82 neutrons