Convalent bonds
The number of atoms of a particular element in a compound can vary depending on the chemical formula of the compound. You can determine the number of atoms by looking at the subscripts in the chemical formula. For example, in H2O (water), there are 2 hydrogen atoms and 1 oxygen atom.
Hydrogen is present in the greatest number of atoms, if that is what is meant by "particles" in the question.
ionic compound
Yes, the element changes to compound when atoms of it changes because compound is made up of different types of element and the element is made up of different types of atoms when the atoms are changed the element also changes and different types of elements are made due to this the element is changed to a compound.
Compound
Ammonia is a compound composed of nitrogen and hydrogen atoms.
covalent compound
Subscripts in a compound are used to indicate the number of atoms present for each element in the compound. They show the ratio at which the elements are combined to form the compound. Each subscript number represents the number of atoms of the element that follows it.
It varies with the compound.
That's because of the way "compound" is defined. If atoms of an element combine with other atoms of the SAME element, then it's not called a "compound".
Same type of atoms.
It is important to know the relative number of atoms of each element in a compound for the chemical composition.