Atomic & Mass Number Flashcards

All 6 cards in this deck

What is the atomic number of an atom?

The number of protons in its nucleus.

What is the mass number of an atom?

The total number of protons and neutrons in the atom.

In the nuclear symbol $^{A}_{Z}X$, what do $A$ and $Z$ stand for?

$A$ is the mass number; $Z$ is the atomic number (number of protons).

What are the steps to find the number of neutrons in an atom from its nuclear symbol?

e.g. $^{7}_{3}\text{Li}$

1. Read the mass number (top): $7$
2. Read the atomic number (bottom): $3$
3. Neutrons = mass number − atomic number = $7 - 3 = 4$

What decides which element an atom is?

Its number of protons (atomic number) — all atoms of an element have the same number of protons.

True or false? Two atoms with the same mass number must be the same element.

False. Only the same atomic number (number of protons) means the same element.