your answer is <u>D</u><u>.</u><u> </u>physical change, because a new substance is not formed.
Lots of igneous rock underneath sedimentary rocks
A scientist would measure the amount of carbon-14 (¹⁴C) in a fossil to determine its age.
The ¹⁴C:¹²C ratio is constant in living organisms. When they die, the radioactive ¹⁴C decays, so the ratio changes. The half-life for the for the decay is 5730 a, so scientists can work backwards and calculate how long ago the plant died. The method is good for determining the age of fossils up to 50 000 a old.
Answer:
Answer in explanation
Explanation:
To answer the question, we know that the atomic mass is the sum of the number of protons and neutrons. The number of protons equals the number of electrons in an electrically neutral atom. For positively charged ion, there is loss of electron, we subtract the charge from the number of protons. For negatively ion, there is a gain of electron, we add the charge to the number of protons
A 81Br- has gained one electron
P = 35
N = 81 - 35 = 46
E = 35 + 1 = 36
B. 63Cu2+ has lost 2 electrons
P = 29
N = 63 - 29 = 33
E = 63 - 2 = 61
C. 18O2- has gained 2 electrons
P= 8
N = 18 - 8 = 10
E = 8 + 2 = 10
D. 14C is electrically neutral P = E
P = 6
N = 14 - 6 = 8
E = 6