1. Ca → Element
2. Proton → positive
3. H2O → compound
4. Fission → nuclear decay
5. Fusion → Nuclear synthesis
6. η → Neutron
7. e → electron
8. Atomic number → no of protons in nucleus.
Explanation
1. Ca (Calcium):
Calcium is an element with the atomic number of 20. It is an alkaline earth metal. The 99% of calcium is found in our bodies, in bones, teeth.
2. Proton:
Proton is a subatomic particle and it holds the positive charge. Proton is present in the nucleus of the atom.
3. H2O (water):
Water is a chemical compound and it's chemical formula is H2O. It's called compound as it contains 2 hydrogen and 1 oxygen atoms bonded together through the covalent bond.
4. Fission:
Fission is a process in which large massive unstable nucleus splits into the smaller, less heavier and stable nuclei. The energy is re;eased in the form of radiations during this process. It's called as the radioactive decay.
5. Fusion:
Fusion is opposite of the fission reaction. As in this case the two nuclei combines to form a single large nucleus. That's why it is a nuclear synthesis process.
6. η neutron:
Neutron is a subatomic particle and it is a neutral particle which is located inside the nucleus. n is a symbol used for the neutron.
7. e Electron:
The symbol for electron is e. It's a subatomic particle with negative charge. It is found in the orbits around the nucleus.
8. Atomic Number:
Atomic number is defined as the number of protons in the nucleus of an atom. IT is represented by Z.
Answer:
C. crust, mantle, core
Explanation:
density increases as you travel from the crust to the inner core
the crust is on top
next is the mantle
and then the core
<u>Answer:</u> The Young's modulus for the wire is 
<u>Explanation:</u>
Young's Modulus is defined as the ratio of stress acting on a substance to the amount of strain produced.
The equation representing Young's Modulus is:

where,
Y = Young's Modulus
F = force exerted by the weight = 
m = mass of the ball = 10 kg
g = acceleration due to gravity = 
l = length of wire = 2.6 m
A = area of cross section = 
r = radius of the wire =
(Conversion factor: 1 m = 1000 mm)
= change in length = 1.99 mm = 
Putting values in above equation, we get:

Hence, the Young's modulus for the wire is 