Build the Lightest Molecule

Why it matters

Hydrogen is the lightest stuff in the universe — so light it floats out of your hand, and so lonely-shelled it never travels alone. Two tiny atoms grab each other's electron and ride as a pair: H₂.

Predict first

Why does hydrogen gas exist as H₂ molecules rather than single H atoms?

Hydrogen has atomic number 1, meaning 1 proton and 1 electron. To achieve a stable duet (like helium), two hydrogen atoms share their electrons, forming a covalent bond in H₂.

• Single atoms are too heavy to float
• Each atom needs one more electron to fill its shell, so they share — correct
• Hydrogen atoms repel each other strongly
• It is a random accident of nature

What you do

Each hydrogen atom has just one electron and a half-empty shell. Share one pair between two H atoms and snap them into H₂ — the lightest molecule in the universe.

Check yourself

What is the atomic number of hydrogen?

Atomic number equals the number of protons. Hydrogen has 1 proton.

In a neutral hydrogen atom, how many electrons are present?

A neutral atom has equal numbers of protons and electrons. Since Z=1, there is 1 electron.

Why is hydrogen diatomic (H₂)?

Hydrogen atoms share electrons to fill their first shell (duet rule), forming a stable H₂ molecule.

• 0
• 1 — correct
• 2
• 18
• 0
• 1 — correct
• 2
• 1.5
• To increase its atomic mass
• To achieve a stable electron configuration by sharing — correct
• Because it has 2 protons
• To become a metal