Negative ions
The number and arrangement of protons in an atom's nucleus determine the element it is. Each element has a unique number of protons, known as the atomic number, which distinguishes it from other elements.
Protons remain constant for a specific element, as they determine the element's identity. Electrons can vary but generally match the number of protons for a neutral element. Neutrons can vary slightly within isotopes of an element.
An atom of an element is comprised of protons, electrons, and usually neutrons. The specific element is determined by the number of protons, and so there is only one particle that determines the element.
Inside of an atom there are protons and neutrons. The protons determine the element whereas the neutron can determine if it is an isotope of that element. Of course there are many smaller particles inside of protons and neutrons like quarks and gluons and ... strings.
To determine the number of neutrons in an element, subtract the atomic number (number of protons) from the atomic mass (rounded to the nearest whole number). Neutrons are neutral particles found in the nucleus of an atom.
The atom is the smallest particle of an element that retains it's characteristics. Sub-atomic particles such as protons, neutrons and electrons form the atom and it is the amount of each of these sub-atomic particles that make the element that element.
You can determine what element an atom is by it's amount of sub-atomic particles and their positions. Every element has a different amount of electrons, so that is the easiest way to determine what type an atom is. If you wanted to determine it more broadly, for example, which group an element was in, you could just count the amount of electrons in the outer shell, as each group is unique in this way.
essentially that's what a lot of elements are, but what makes an element a new element is if it can be reproduced and be stabilized for an amount of time
electrons
It is the number of positely charged nuclear particles ( protons ).
i don't know about 2
The simplest form of an element is an atom. Subatomic particles are not a form of the element; they are a "building block" of an element.