Answer:
The number of protons or electrons in its atomic structure
Step-by-step explanation:
Elements are substances which constitute the building block of matter. The smallest particles of elements that can ever exist are known as atoms. Atoms of different elements are different in their structure properties. This difference is due to to the number of sub-atomic particles present in the atom of each element.
The three sub-atomicparticles are protons, neutrons and electrons. Protons and neutrons are present in the nucleus of an atom, while the electrons revolve around the nucleus in orbits. The identity of each element is determined by the number of protons present in the atomic nucleus of that element. This is known as the atomic number of that element. For neutral atoms, the proton number is equal to electron number.
For the given element, the electron and proton number are respectively 4, therefore, the atomic number of the element is 4. The element with atomic number 4 is Beryllium.