B. It is open to change as new evidence or data is discovered. If scientists discover new evidence, they must modify their theories to conform with the new data.
A. is <em>incorrect</em>. Scientific laws are so well established that there can be no exceptions.
C. is <em>incorrect</em>. A scientific theory is the collective judgement of scientists as to the best explanation for a phenomenon. A new observation may require modification of the theory.
D. is <em>incorrect</em>. Advancements in technology can provide new evidence that requires new explanations.
Answer:
no dont worry its in decimal point
anything after the point is considered as not to the fullest
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).
First of all write a balanced equation.
4Na + O2 -> 2Na2O
You are starting with a mass of sodium. You need to use sodium’s molar mass. Take this quantity times mole to mole ratio between sodium and sodium oxide to get moles of sodium oxide produced.
.141 moles of sodium oxide produced
Answer:
detail is given below.
Explanation:
The charged particles of nucleus are protons while neutrons are neutral having no charge.
We know that an atom consist of electrons, protons and neutrons. Neutrons and protons are present inside the nucleus while electrons are present out side the nucleus.
Electron has a negative charge and is written as e⁻. The mass of electron is 9.10938356×10⁻³¹ Kg . While mass of proton and neutron is 1.672623×10⁻²⁷Kg and 1.674929×10⁻²⁷ Kg respectively.
Symbol of proton= P⁺
Symbol of neutron= n⁰
The number of electron or number of protons are called atomic number while mass number of an atom is sum of protons and neutrons.
one proton contribute 1 amu to the total weight. There are 20 protons and 20 neutrons in Ca thus its atomic mass is 40 amu.
While the atomic number is 20.
