State the relative charge and relative mass of a neutron.

Relative charge 0, relative mass 1.

State the relative charge and relative mass of an electron.

Relative charge −1, relative mass 1/1840.

What is the atomic (proton) number?

The number of protons in the nucleus of an atom; it defines the element.

What is the mass number?

The total number of protons plus neutrons in the nucleus of an atom.

How do you find the number of neutrons?

Mass number − atomic number (A − Z).

How many electrons are in an ion with charge 2+?

Z − 2: the ion has lost two electrons, while its number of protons is unchanged.

Atoms of the same element with the same number of protons but different numbers of neutrons.

Why do isotopes of an element have the same chemical properties?

They have the same number of electrons, so the same electron arrangement; neutrons have no charge.

Why can isotopes differ in physical properties such as density?

They have different numbers of neutrons and so different masses.

What did the few alpha particles that rebounded show?

That the atom has a very small, dense, positively charged nucleus containing most of the mass.

Fundamental particles, mass number and isotopesAQA A-Level Chemistry: Flashcards

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State the relative charge and relative mass of a proton.

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State the relative charge and relative mass of a proton.: Relative charge +1, relative mass 1.
State the relative charge and relative mass of a neutron.: Relative charge 0, relative mass 1.
State the relative charge and relative mass of an electron.: Relative charge −1, relative mass 1/1840.
Which two particles are found in the nucleus?: Protons and neutrons.
What is the atomic (proton) number?: The number of protons in the nucleus of an atom; it defines the element.
What is the mass number?: The total number of protons plus neutrons in the nucleus of an atom.
How do you find the number of neutrons?: Mass number − atomic number (A − Z).
How many electrons are in an ion with charge 2+?: Z − 2: the ion has lost two electrons, while its number of protons is unchanged.
Define isotopes.: Atoms of the same element with the same number of protons but different numbers of neutrons.
Why do isotopes of an element have the same chemical properties?: They have the same number of electrons, so the same electron arrangement; neutrons have no charge.
Why can isotopes differ in physical properties such as density?: They have different numbers of neutrons and so different masses.
What did the few alpha particles that rebounded show?: That the atom has a very small, dense, positively charged nucleus containing most of the mass.

Exam questions on Fundamental particles, mass number and isotopes

In 1909 Geiger and Marsden, working with Rutherford, fired a beam of positively charged alpha particles at a very thin sheet of gold foil and recorded where each particle landed using a detector screen. At the time, the accepted 'plum pudding' model pictured an atom as a sphere of positive charge with electrons embedded throughout it.
Explain how the results of this experiment led scientists to conclude that the nucleus is positively charged and that it contains most of the mass of the atom.2 marks
A forensic laboratory identifies an iron compound in a paint sample. The iron is present as the ion ⁵⁶Fe³⁺, and the analyst's data sheet gives the atomic number of iron as 26.
A second sample contains the ion ⁵⁴Fe²⁺. State the number of protons, the number of neutrons and the number of electrons in one ⁵⁴Fe²⁺ ion.2 marks
Magnesium has three naturally occurring isotopes, ²⁴Mg, ²⁵Mg and ²⁶Mg. A chemist is comparing atoms of these isotopes. The atomic number of magnesium is 12.
Explain what is meant by the term isotopes, and state the number of protons, neutrons and electrons in an atom of ²⁵Mg.3 marks

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Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).