The Element Identity Card

Why it matters

Imagine a substance so pure that every single particle inside it is an identical twin of every other. Cut it, melt it, or crush it, and its fundamental identity never changes.

Predict first

If you isolate a single atom from a block of pure gold, what defines it as 'gold'?

The atomic number (proton count) is the element's unique fingerprint. Change the protons, and you change the element.

• Its shiny yellow color
• The number of protons in its nucleus — correct
• The number of electrons it shares
• Its weight compared to other metals

What you do

Every element carries an identity card. Sort these eight: shiny, conducting metals; dull non-metals; or aloof noble gases that react with almost nothing.

Check yourself

Which property is used to classify elements into metals, non-metals, and metalloids?

While atomic number defines identity, properties like conductivity, malleability, and reactivity help us group elements into metals, non-metals, and metalloids.

Why is water (H₂O) not considered an element?

An element contains only one kind of atom. Water contains hydrogen and oxygen atoms chemically combined, making it a compound.

If you have a sample of pure oxygen gas (O₂), what is true about its particles?

Many elements, like oxygen, exist as molecules. O₂ is an element because all atoms in the molecule are the same type.

• Their color and smell
• Their physical and chemical properties like conductivity — correct
• The number of neutrons they contain
• Because it is a liquid at room temperature
• Because it is made of two different kinds of atoms bonded together — correct
• Because boiling it turns it into steam
• Because it is found in nature
• Each particle contains two oxygen atoms — correct
• Each particle is a single oxygen atom
• The particles are a mix of oxygen and nitrogen