Which is the only non metal that is placed on the left side of the modern periodic table along with the alkali metals?

Introduction / Context:
The modern periodic table is arranged so that metals, non metals and metalloids occupy characteristic regions. Most non metals are found on the right side of the table, while metals occupy the left and centre. However, there is one important exception among the non metals that is placed on the far left in group 1, above the alkali metals. This special positioning reflects both its electron configuration and its unique properties. The question asks you to identify this non metal that appears on the left side of the periodic table.

Given Data / Assumptions:

• Group 1 of the periodic table is the alkali metal group, including lithium, sodium and potassium.
• Hydrogen is often shown above lithium in group 1, but it is not a metal under normal conditions.
• Most other non metals such as carbon, nitrogen, oxygen, halogens and noble gases are located on the right side of the table.
• The question is about position in the standard table layout, not specialised versions.

Concept / Approach:
Hydrogen has atomic number 1 and an electronic configuration of 1 electron in its first shell. This resembles the outer electron configuration of alkali metals, which each have one electron in their outermost shell. For this reason, hydrogen is placed in group 1 at the top. However, hydrogen is a non metal gas at room temperature and has many properties quite different from alkali metals. Carbon, neon, helium and chlorine are all non metals but are located on the right side of the table, not in group 1. The approach is to recognise that hydrogen is the only non metal placed in the leftmost column.

Step-by-Step Solution:
Step 1: Recall that the alkali metals (group 1) are lithium, sodium, potassium, rubidium, cesium and francium. Step 2: Above lithium in this group, the element usually shown is hydrogen with atomic number 1. Step 3: Hydrogen is a non metal gas under standard conditions and forms covalent molecules such as H2. Step 4: Carbon is located in group 14 near the middle right of the table, not in the leftmost column. Step 5: Neon and helium are noble gases in group 18 on the far right side of the periodic table. Step 6: Chlorine is a halogen in group 17, also on the right side. Step 7: Therefore, hydrogen is the only non metal positioned on the left side with the alkali metals.

Verification / Alternative check:
Looking at any standard periodic table chart confirms this layout. Group 1 shows hydrogen at the top followed by the alkali metals. Textbooks often describe hydrogen as a special case that does not fit neatly into any one group, but for convenience it is placed above the alkali metals. The non metals carbon, nitrogen, oxygen, halogens and noble gases form a cluster on the right side, separate from the main metallic block. These consistent representations across many sources confirm that hydrogen is the only non metal found on the leftmost side.

Why Other Options Are Wrong:
Option B, carbon, is a non metal but is located in the p block on the right side, not in the leftmost group. Option C, neon, and option D, helium, are noble gases in group 18, at the right edge of the table. Option E, chlorine, is a halogen in group 17 next to the noble gases. None of these occupy the leftmost column with the alkali metals. Only option A, hydrogen, is both a non metal and placed in group 1 on the left side of the periodic table.

Common Pitfalls:
Some students mistakenly assume that hydrogen must be a metal because it appears with metals in group 1. Others forget that group placement is based on electronic configuration and that hydrogen is unique in having properties similar to both alkali metals and halogens. To avoid confusion, remember that hydrogen is non metallic but is placed in group 1 mainly due to having one valence electron. This special status makes it an exception among non metals and explains its unusual position.

Final Answer:
The only non metal placed on the left side of the modern periodic table with the alkali metals is Hydrogen.