Answer:
Explanation:
The half-life of Na-24 (15 h) is the time it takes for half of it to decay.
After one half-life, half (50 %) of the original amount will remain.
After a second half-life, half of that amount (25 %) will remain, and so on.
We can construct a table as follows:
No. of Fraction Mass
<u>half-lives t/da Remaining Remaining/g
</u>
0 0 1 18
1 15 ½ 9.0
2 30 ¼ 4.5
3 45 ⅛ 2.2
4 60 ⅟₁₆ 1.1
5 75 ⅟₃₂ 0.56
6 90 ⅟₆₄ 0.28
We see that 
remain after five half-lives (75 h).
Ca, V, Cu, Kr
Remember a period is a the horizontal rows in the Periodic Table.
Answer:
c. Hfus is always negative.
Explanation:
Because energy is released when fusing solids
Answer:
Carbon dioxide is an atmospheric constituent that plays several vital roles in the environment. It is a greenhouse gas that traps infrared radiation heat in the atmosphere. It plays a crucial role in the weathering of rocks. ... It is stored in biomass, organic matter in sediments, and in carbonate rocks like limestone.
Explanation:
Answer:
It enables us to predict properties of elements, and possibly foresee future benefits and uses based on a better understanding.
