Explanation:
- When a bond is formed by transfer of electrons from one atom to another then it results in the formation of an ionic bond.
An ionic bond is generally formed by a metal and a non-metal.
For example, lithium is an alkali metal with atomic number 3 and its electronic distribution is 2, 1.
And, chlorine is a non-metal with atomic number 17 and its electronic distribution is 2, 8, 7.
So, in order to complete their octet lithium needs to lose an electron and chlorine needs to gain an electron.
Hence, both of then on chemically combining together results in the formation of an ionic compound that is, lithium chloride (LiCl).
An ionic compound is formed by LiCl because lithium has donated its valence electron to the chlorine atom.
- On the other hand, if a bond is formed by sharing of electrons between the two chemically combining atoms then it is known as a covalent bond.
For example, 
is a covalent compound as electrons are being shared by each oxygen atom.
The answers are
The age of the oldest stars
How fast distant galaxies are moving away from us
Patterns of background radiation.
Explanation:
The Astronomers calculate the age of the universe by looking for oldest stars, and by measuring the rate of expansion of the universe and back to big bang.
The Astronomers used the techniques like the age of oldest stars, how fast the distant galaxies are moving away from us, patterns of background radiation and along with the Big Bang as reference point, they estimate that the universe may be approximately 12 billion years old.
Answer:
Loses
Explanation:
liquid changes into solid, heat is released. The energy released upon freezing, known as the enthalpy of fusion, is a latent heat, and is exactly the same as the energy required to melt the same amount of the solid.
Answer:
Yes.
Explanation:
If you want to use the least fuel, then missions to Mars are feasible every two years.
You want to launch when Earth and Mars are close together, and this happens <em>about every 26 months</em>.
However, Earth travels faster than Mars, so the spaceship must launch when Mars is 44° <em>ahead </em>of Earth in its orbit.
The ship will then use the most efficient trajectory to arrive at Mars.
Answer:
235 U ( the isotope of uranium with mass number 235) and 239Pu(the isotope of plutonium with mass number 239
Explanation:
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