Lanthanum-138 has a half-life of 105 billion years. after 525 billion years, how much of a 240 g sample of this radioisotope will remain?

nevermind, i got 7.5g and was right

Which of the following statements is true? a. elements in the last period are radioactive. b. atomic weight is the same as atomic mass. c. elements in the same group have the same number of electron shells. d. atomic number equals the number of neutrons in the nucleus of an atom.

In the following redox reaction which is the oxidizing agent and which is the reducing agent? alcl3 + na nacl + al

Which set of characteristics best describes igneous rock? a) largest type of rock, made of organic matter, hardest type of rock b) least abundant type of rock, made of other rocks, made mostly of minerals c) found on all continents, contains wavy bands of stripes, contains fossils d) most abundant type in earth's crust, made of magma/lava, contains no fossils