Helium is before lithium on the periodic table because the periodic table arranges elements by increasing

atomic number

Explanation:

The chemical elements are organized according to several of their physical and, especially, chemical properties, the most important being the atomic number. However, these elements can be organized in different ways within the periodic table, without them losing their assigned place within it, all to achieve a better study of such elements. Thus, the elements can be divided into the table in several ways, depending on the property to be studied or of interest:

- Periods and groups.

- Representative elements, transition, internal transition and noble gases.

- Metal, non-metal and metalloid elements.

- Element families.

In any case, each chemical element has a fixed place in the periodic table in the form of a small square, or square, within which there are numbers, words and letters, which constitute the physical and chemical information of that element.

Atomic number of helium : 2

Atomic number of lithium : 3

Atoms of different elements have different numbers of protons. The atomic number - which is identified by the letter Z, by the German term zahl - indicates the number of protons that are present in the nucleus of an atom.

The atomic number defines the electronic configuration of the atom and allows the ordering of the different chemical elements in the periodic table, which begins with hydrogen (Z = 1) and continues with helium, lithium, beryllium, boron, carbon and nitrogen

It is important to keep in mind that an unaltered atom is electrically neutral: therefore, its atomic number will always be the same as its number of electrons. The atomic number also defines the level of filling of the successive electronic orbitals of the atom, a characteristic that really reflects the periodic table.

answer: a. same unit

explanation: