An ionic compound is a compound between a metal and a non metal where the metal (normally from group 1 or 2) transferrs an electron to the non metal ( most commonly from group 6 or 7) . this is so that both atoms have a full outer shell of electrons. the metal gains a positive charge and the non metal a negative charge. they are held together by electrostatic forces of attraction. an example would be sodium chloride (salt) sodium is in group 1 and chlorine in group 7 so sodium transfers one electron :)
People firstly believe that the planets move in a circular orbit until Newton came up with his hypothesis by inventing calculus so that we could understood and calculated planetary orbits and their accuracy.
<u>Explanation:</u>
- Everyone assumed the planets were perfect circles until Newton came up with an idea. Slowly people would make maps of the orbits that added circles on circles, and they could never really explain about the movement of the planet. They simply say that planets move on circles but they lacked the math to explain or prove it. Then Newton came up with an idea of inventing calculus so that we could understood and calculated planetary orbits and their accuracy.
- Firstly people used their observations and say that the orbits looked like circles, then they developed their models and did the math, and proposed their hypothesizes which were wrong, until Newton came along and tried to match a model that used elliptical orbits and invented the math that allowed him to make predictions with it. His model worked for most planets.
- However he could not explain about the planet Mercury for instance since it was a very strange orbit. Then after the Einstein's theory of General Relativity he could also explain very deeply about it.
- Scientists and Astronomers made hypothesizes that there was another planet orbiting too close to the sun to see with telescopes, called Vulcan, that explained mercury's orbit before Einstein's theory. Then long after we had telescopes which was good enough to see if there was a planet orbiting closer to the sun than mercury.
Answer:
Ron and Hermoine
Explanation:
They always fought over petty things, but at the end, they did end up together!
(Answer for your question about love and friendship being a central theme in Harry Potter and the Philosopher's stone)
*ALSO, MY ANSWER MIGHT BE WRONG* so be sure to use a pencil just in case!
Steam is the gaseous phase of water. It is used in some cases to melt ice. Melting of ice is the conversion of solid water to liquid water. This is just a phase change in which water changes its state from solid state to liquid state. But the chemical composition of water 
remains unchanged. Water has the same molecular formula in both the solid (ice) and liquid states. Hence, the conversion of solid ice to liquid water by steam refers to a physical change.
Answer:
Some elements have variable valencies because of the different electronic configurations. An atom of an element can sometimes lose more electrons than are present in its valence shell i.e. loss from the penultimate shell and hence exhibit more than 1 or variable valency.
Explanation:
Hope it helps.
