Atomic Structure — Drills · Grade 8 Science

What these drills covers

By the end of Atomic Structure you should be able to:

I can identify the three subatomic particles and describe their charge, mass, and location in the atom.
I can use an element's atomic number and mass number to find its numbers of protons, neutrons, and electrons.
I can distinguish molecular and extended-structure models.

8 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: atom, proton, neutron, electron, nucleus, atomic number, mass number, isotope, ion, model, evidence, system boundary, assumption.

Problem 1

Which particle has no electric charge?

Proton
Neutron
Electron
Ion

Answer and explanation

Neutron

Neutrons are neutral. Protons are positive and electrons negative.

Problem 2

An atom has 11 protons and 12 neutrons. What is its mass number?

Answer and explanation

Mass number = protons + neutrons = 11 + 12 = 23.

Problem 3

A neutral atom has 17 protons. How many electrons does it have?

Answer and explanation

A neutral atom has equal numbers of protons and electrons.

Problem 4

Almost all of an atom's mass is in the

electron cloud
nucleus
outer shell
empty space

Answer and explanation

nucleus

Protons and neutrons sit in the nucleus and are each about 1,800 times the mass of an electron.

Problem 5

An atom has mass number 40 and 20 neutrons. How many protons does it have?

Answer and explanation

Protons = mass number − neutrons = 40 − 20 = 20.

Problem 6

Two atoms have the same number of protons but different numbers of neutrons. They are

different elements
ions of each other
isotopes of the same element
identical

Answer and explanation

isotopes of the same element

The proton count fixes the element; a different neutron count makes an isotope.

Problem 7

An atom loses one electron and ends with 11 electrons and 11 protons before the loss. What is its charge after, as a signed whole number?

Answer and explanation

Losing a negative electron leaves one more proton than electron, giving a charge of +1.

Problem 8

Why does the number of protons, rather than the number of neutrons, decide which element an atom is?

Answer and explanation

The proton count is what distinguishes one element from another: every carbon atom has 6 protons, and an atom with 7 protons is nitrogen instead. Neutron count can vary within the same element, producing isotopes that are still that element, so neutrons cannot be what defines it.

Response criteria

State a scientifically accurate conclusion.
Show the data, mechanism, or calculation that supports it.
Include units, conditions, or limits where relevant.

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