Isotopes Atomic Number Atomic number number of protons

Isotopes

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

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

Illustrating isotopes/nuclides Nuclear Notation: 12 Hyphen Notation: C-12 6 C

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

Problems – determine the # of p+, n, and e- in each of these. 1. Sodium-23 1. 11 p+, 11 e-, 12 n 2. calcium-40 2. 20 p+, 20 e-, 20 n 3. 4. 64 29 108 47 Cu Ag 3. 29 p+, 29 e-, 35 n 4. 47 p+, 47 e-, 61 n

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

Answers 28 • 5. 14 Si 56 • 6. 26 Fe 138 • 7. 56 Ba silicon-28 iron-56 barium-138