Answer: (3) silicon
Explanation:
Element is a pure substance which is composed of atoms of similar elements.It can not be decomposed into simpler constituents using chemical reactions.Example: Silicon (Si)
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: ethane 
, propanone 
and water 
Answer:
The Aufbau Principle
Explanation:
In the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy level before occupying higher-energy levels.
Answer:
Volcanoes cool off the earth by emitting heat from its interior. They also add islands and for example, Hawaii was created / is made out of volcanoes. The deposits from volcanoes can also be used for building materials. Volcanic explosions have caused the atmosphere and oceans to form. Volcanic deposits also create land which is fertile.
Addition of boiled, deionized water to the titrating flask to wash the wall of the erlenmeyer flask and the buret tip will have no effect on the Ksp value of ca(oh)2.
There will be no effect on the Ksp value as boiled deionised water is not able to alter the number of hydronium and hydroxide ions. As no change in the ions happen so there will be no change in Ksp value. The equilibrium constant for a solid material dissolving in an aqueous solution is the solubility product constant, Ksp. It stands for the degree of solute dissolution in solution. A substance's Ksp value increases with how soluble it is.
To know more about, solubility product constant, click here,
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