Answer:
The answer to the question is
50 % of the original amount of potassium 40 will be left after one half life or 1.25 billion years
Explanation:
To solve the question we note that the half life is the time for half of the quantity of substance that undergoes radioactive decay to disintegrate, thus
we have
half life of potassium 40 K₄₀ = 1.25 billion years
To support the believe tht the rock was formed 1.25 billion years ago we have
After 1.25 billion years we have
= 
=0.5 of 
will be left or 50 % of the original amount of potassium 40 will be left
It proposed that the positive charge was concentrated in the nucleus.
i just took the test. this is right.
Answer:
The answer to your question is: The first option.
Explanation:
Outer electron shell because these electrons can be readily exchanged with adjacent atoms As is mentioned in the statement, these electrons can be exchanged easily with adjacent atoms, so this is the right answer.
Innermost electron shell because the electrons can be transferred to the nucleus. Innermost electrons can not react as easily as the outermost, because they are protected by the outermost shells. This answer in not correct.
Middle electron shell because they are intermediate in distance between the nucleus and the adjacent atom that bonds with the atom. In order that an electron can react, it must be located in the outermost shell, it is not an advantage to be in the middle shells. This option is incorrect.
Any electron can exchange with adjacent atoms to form a bond; there is no preference. Not any electron can react with another element, only the electrons in the outermost shell can react, this option is incorrect.
Answer: sorry its lagging i hope this help fore 18.. =D
Explanation:
n,s is repeating the cycle of the inside
