ISOTOPES AND ATOMIC MASS GRADE 8 LEVEL.pptx

PPT ABOUT ISOTOPES AND ATOMIC MASS

1. ISOTOPES AND ATOMIC MASS GRADE – 8

2. ATOMIC NUMBER The atomic number is the number of protons in the nucleus of an atom. Example: Carbon  Atomic Number = 6  6 Protons

3. ATOMIC MASS The weighted average mass of all the naturally occurring isotopes of an element. Example: Chlorine  35.45 (average of Cl-35 and Cl-37)

4. ISOTOPES Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. Same Element  Same Atomic Number (Z) Different Neutrons  Different Mass Number Example: Carbon-12, Carbon-13, and Carbon-14

5. Isotope Protons Neutrons Mass Number Carbon-12 6 6 12 Carbon-13 6 7 13 Carbon-14 6 8 14

6. MASS NUMBER The mass number (A) is the total number of protons and neutrons in an atom’s nucleus. A= Protons + Neutrons Example: Carbon-14  6 Protons + 8 Neutrons = Mass Number (14)

7. RELATIVE ABUNDANCE Relative abundance is the percentage of a certain isotope found in nature. Formula: Average Atomic Mass = (m1 x f1) + (m2 x f2) +…… Where: m= mass of isotope f= fractional abundance (percentage ÷ 100)

8. Example: Chlorine Isotopes Cl-35 = 75% abundance  mass = 35 u Cl-37 = 25% abundance  mass = 37 u Solution: (35 x 0.75) + (37 x 0.25) = 35.5 u ( atomic mass unit ) Average Atomic Mass of Chlorine = 35.5