Thursday, October 1 — Day 25

Neutrons. No treaties. No valence counting.

The clock

Same block. 9:30 start, exam 12:30–1:00, phones off until 1:30.

The idea

Protons name the element. Carbon is carbon because it has 6 protons. That number does not change.

Neutrons are extra weight in the nucleus. They do not change the name. The common carbon atom has 6 neutrons. A carbon atom with 8 neutrons is still carbon. It is a heavier carbon. That is an isotope: same protons, different neutrons.

Electrons in a neutral atom match the protons. Carbon: 6 protons, 6 electrons.

You do not need the group number today. The exam asks protons or neutrons for elements that have not been the daily card.

A few to have:

Argon is the odd one in that list: 18 protons, 22 neutrons, not 18.

Help

• Periodic table
• Evolution timeline