Atomic Number, Mass Number and Isotopes: Concept Map

≈ 30 min

Concept Map

Organise the vocabulary, quantities and relationships into a connected model.

This extension applies that lens specifically to Atomic Number, Mass Number and Isotopes.

Two numbers pin down an atom:

Atomic number ( $Z$ ) = number of protons. It defines which element the atom is — every carbon atom has $Z = 6$ .
Mass number ( $A$ ) = number of protons + neutrons.

So number of neutrons = $A - Z$ . We write an atom as $^{A}_{Z}\text{X}$ , for example $^{23}_{11}\text{Na}$ : 11 protons, $23 - 11 = 12$ neutrons.

Isotopes are atoms of the same element (same $Z$ ) with different numbers of neutrons (different $A$ ). Chlorine has two common isotopes, $^{35}\text{Cl}$ and $^{37}\text{Cl}$ — both have 17 protons, but 18 and 20 neutrons.

Chemistry — Grade 10 — Concept Map: How many neutrons are in an atom of $^{23}_{11}\text{Na}$ ?

Chemistry — Grade 10 — Concept Map: Two atoms both have 17 protons, but one has 18 neutrons and the other 20. They are…

different elements

isotopes of the same element

ions

compounds

Chemistry — Grade 10 — Concept Map: An element has atomic number $Z = 6$ and mass number $A = 14$ . How many neutrons does this atom have?

Name the original topic being extended by this concept map lesson.

Which statement is the best evidence-led starting point for Atomic Number, Mass Number and Isotopes: Concept Map?

Two numbers pin down an atom: - Atomic number ( $Z$ ) = number of protons. It defines which element the atom is — every carbon atom has $Z = 6$ . - Mass number ( $A$ ) = number of protons + neutrons. So number of neutrons = $A - Z$ . We write an atom as $^{A}_{Z}\text{X}$ , for example $^{23}_{11}\text{Na}$ : 11 protons, $23 - 11 = 12$ neutrons

Pure Substances and Mixtures

Elements and Compounds

A conclusion needs no observations, calculations or stated assumptions.