How are elements arranged on the periodic table?

How are elements arranged on the periodic table?

• A. Increasing atomic mass is the primary organizing factor.
• B. Increasing atomic number; grouped by similar chemical properties.
• C. Alphabetical order by element symbol.
• D. Arrangement is random.

Answer: (B)

Elements are arranged on the periodic table by increasing atomic number, and they are grouped so that elements with similar chemical properties fall in the same columns. The atomic number is the number of protons in the nucleus (and, for a neutral atom, the number of electrons), which largely determines the electron configuration, especially the valence electrons that control bonding and reactivity. As you move left to right across a period, the nuclear charge increases while the outer-shell pattern changes gradually, producing recurring, predictable trends in properties. Moving down a group adds energy levels, but the outer electron arrangement stays similar enough to keep comparable chemistry within the column. This organization aligns with how elements actually behave, a relationship confirmed by Moseley’s work showing a direct link to atomic number rather than atomic mass. For instance, all members of a group like the alkali metals have one valence electron and similar reactivity, while halogens have seven, and noble gases have full outer shells. So the best description is that elements are arranged by increasing atomic number and grouped by similar chemical properties.

Elements are arranged on the periodic table by increasing atomic number, and they are grouped so that elements with similar chemical properties fall in the same columns. The atomic number is the number of protons in the nucleus (and, for a neutral atom, the number of electrons), which largely determines the electron configuration, especially the valence electrons that control bonding and reactivity. As you move left to right across a period, the nuclear charge increases while the outer-shell pattern changes gradually, producing recurring, predictable trends in properties. Moving down a group adds energy levels, but the outer electron arrangement stays similar enough to keep comparable chemistry within the column. This organization aligns with how elements actually behave, a relationship confirmed by Moseley’s work showing a direct link to atomic number rather than atomic mass. For instance, all members of a group like the alkali metals have one valence electron and similar reactivity, while halogens have seven, and noble gases have full outer shells. So the best description is that elements are arranged by increasing atomic number and grouped by similar chemical properties.