Answer:
3
Explanation:
The half-life of a radioactive isotope is the time it takes for the mass of the sample to halve.
This can be rewritten as follows:
where
m(t) is the mass of the sample at time t
m0 is the original mass of the sample
n is the number of half-lives that passed
We see that if we take n=3, the amount of original sample left is
So 3 (3 half-lives) is the correct answer.
d = distance traveled by her on her bicycle on a long flat road = 24 kilometer
t = time taken by her to travel distance "d" on her bicycle on a long flat road = 1.2 hours
v = average speed of vivian = ?
we know that average speed is given as
v = d/t
inserting the values in the above formula
v = 24 kilometer / 1.2 hour
v = 20 kilometer/hour
hence the correct choice is
C) 20 km/h
Answer:
The sum of positive and negative charges in a unit of Al2O3 equals zero.
Aluminium has a charge of +3 while Oxygen has a charge of -2 on each ion.
Al203 has 2 Al atoms and 3 O atoms.
Charge on Al2O3 = 2(charge on Al ion) + 3(charge on O ion)
= 2(3) + 3(-2)
= 6 - 6
= 0
Explanation:
Aluminium has 3 electrons in the outermost shell and has the tendency to lose those 3 electrons to form a positive ion and have a complete outermost shell.
Whereas, Oxygen has 6 electrons in the outermost and has the tendency to accept two more electrons to form a negative ion and have a complete outermost shell.
Answer:
A
Explanation:
Becuse its complete number
The atomic number tells you the number of protons in an atom. This value never changes because the number of protons in the nucleus always remains constant. The mass number tells you the number of protons and neutrons (or nucleons) together: protons + neutrons = mass number. Since the number of neutrons in the nucleus varies, you can have different amounts of neutrons in the same type of atom. These varied types are called isotopes.
Hope this helps.
