A uranium-235 sample starts with 200 atoms, and 700 million years later, there are 100 atoms. What is the half-life of uranium-235?

A. 350 million years

B. 235 years

C. 100 years

D. 700 million years

How do scientists determine the elements present in different stars

In any good experiment, the scientist needs to (fill in the blank) the hypothesis.

The energy levels for electrons vary from one element to another. True or False

If element x has 88 protons, how many electrons does it have

Remembering the Battle of Bunker Hill what did general Harry and his troops do

J. J Thompson proposed that atoms were made up of positively charged particles with electrons scattered into them. How did he reach this conclusion?

A bathroom scale is compressed 0.21 in. when a 210 -lb person stands on it. Assuming that the scale behaves like a spring that obeys Hooke's law, how much does someone who compresses the scale 0.06 in.

Explain what happens when a ferromagnetic material is made into a permanent magnet.

You are drawing a branching diagram to show the relationship between Turtles frogs and alligators which two organisms does the diagram indicateas having the most recent common ancestor

Estimate the length of the neptunian year using the fact that the earth is 1.50Ã108km from the sun on average.