The factor in determining how an atom reacts is the valence electrons, ie how many and in what energy level.
Electrons in the outer shell, also known as valance electrons, determine how an atom will react. To be more precise I should add that there are transition state elements whose reactivity is also influenced by some of the inner electrons as well.
The atomic number, which is the number of protons in the nucleus, determines what kind of atom it is.
The electron configuration of an atom determines how it behaves when it comes into contact with another atom.
Neutron
chemical change
the number of protons determines the atom.
angles
i am pretty sure that it is the mass and temperature of the atom
Mass Number
The number of protons determines the element's atomic number. When combined with the number of neutrons, it determines the element's atomic mass.
The number of protons, which are found in the nucleus of an atom.
The number of protons and electrons in an atom determine its chemical properties. Specifically, the number of electrons in the outermost energy level (valence electrons) dictates how likely the atom is to react with other atoms to achieve a stable electron configuration.