Percentage Abundance
The element indium has two common isotopes: In–113 (112.90406 u) and In–115 (114.90388 u). If the average atomic mass of indium is 114.818 u, determine its percent isotopic abundances.
4.29 % In–113 and 95.71 % In–115
Rubidium has two common isotopes, 85Rb and 87Rb. If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium?
85.56 amu
Alkali Metals
•very reactive metals that do not occur freely in nature
•good conductors of heat and electricity.
•can explode if they are exposed to water
Metaliods
•have properties of both metals and non-metals
•some of the metalloids are semi-conductors. This means that they can carry an electrical charge under special conditions. This property makes metalloids useful in computers and calculators
1)Protons have a ____ charge:
2)Neutrons Have a _____ charge:
3)Electrons have a ______ charge:
1)Positive
2) Neutral
3) Negative
The element cerium has 4 naturally–occuring isotopes: 0.185 % Ce–136 (135.90714 u), 0.251 % Ce–138 (137.90599 u), 88.45 % Ce–140 (139.90543 u) and 11.114 % Ce–142 (141.90924 u). Determine the average atomic mass of cerium.
140.116 u.
Uranium has three common isotopes. If the abundance of 234U is 0.01%, the abundance of 235U is 0.71%, and the abundance of 238U is 99.28%, what is the average atomic mass of uranium?
237.98 amu
Alkali earth metals
•Metals
•pretty reactive
•not found free in nature
Non- metals
•not able to conduct electricity or heat very well
•very brittle
•Do not reflect light.
Isotope name Atomic Mass # mass # of protons
Uranium 230 92# of nuetrons # of electons Charge
Atomic Number: 92
# of nuetrons: 143
# of electrons: 92
Charge: 0 or nuetral
The element europium has two naturally–occuring isotopes: Eu–151 (150.91985 u) and Eu–153 (152.92123 u). If the average atomic mass of europium is 151.964 u, determine its percent isotopic abundances.
47.81 % Eu–151 and 52.19 % Eu–153.
Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50Ti (5.3%). What is the average atomic mass of titanium?
47.92 amu
Transition Metals
•conduct electricity and heat
Halogens
•"halogen" means "salt-former" and compounds containing halogens are called "salts"
•exist in all three states of matter
42H
Element name:
#of Protons:
# of nuetrons:
Helium
2
2
The element lutetium has two common isotopes: Lu–175 (174.94077 u) and Lu–176 (175.94268 u). If the average atomic mass of lutetium is 174.967 u, calculate its percent isotopic abundances.
97.41 % Lu–175 and 2.59 % Lu–176.
Explain why atoms have different isotopes. In other words, how is it that helium can exist in three different forms?
Neutrons exist to stabilize the nucleus – without them, the nucleus would consist of nothing but positively-charged protons in close proximity to one another. Because there are different ways of stabilizing the protons, there are different isotopes.
Rare Earth Elements
man-made elements
•do not form compounds easily
•Happy/Inert Elements (Full outer shells)
Write the symbol for the isotope:
8 protons 8 Nuetrons
168O
The element lead has 4 common isotopes: 1.4 % Pb–204 (203.97303 u), 24.1 % Pb–206 (205.97445 u), 22.1 % Pb–207 (206.97588 u) and 52.4 % Pb–208 (207.97664 u). Find out the average atomic mass of lead.
207.217 u.
6. Calculate the average atomic mass of bromine. One isotope of bromine has an atomic mass of 78.92amu and a relative abundance of 50.69%. The other major isotope of bromine has an atomic mass of 80.92amu and a relative abundance of 49.31%.
79.90
Other Metals
•are solid, have a high density
Period vs. Groups
Period: Straight across
Group: Up and Down
Calculate the atomic mass of copper if copper-63 is 69.17% abundant and copper-65 is 30.83% abundant.
Answer: 63.62 amu