What are the relative mass and relative charge of a neutron?

Relative mass 1, relative charge 0.

What are the relative mass and relative charge of an electron?

Relative mass 1/1836 (about 0.0005), relative charge −1.

Define atomic (proton) number.

The number of protons in the nucleus of an atom.

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

Why does a neutral atom have no overall charge?

It has equal numbers of protons (+1) and electrons (−1), so the charges cancel.

How many protons, neutrons and electrons are in ²⁷Al³⁺ (Z = 13)?

13 protons, 14 neutrons and 10 electrons (three electrons lost).

How many electrons are in ⁸¹Br⁻ (Z = 35)?

36 electrons (one electron gained).

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 electronic configuration.

Why do isotopes differ in some physical properties?

They have different numbers of neutrons, so different masses; properties such as density and rate of diffusion depend on mass.

Where is most of the mass of an atom found, and why?

In the nucleus, because protons and neutrons each have relative mass 1 whereas electrons have a negligible mass.

Atomic structure and isotopesEdexcel International A Level Chemistry: Flashcards

Card 1 of 130 of 13 known

Question

What are the relative mass and relative charge of a proton?

Tap or press Space to reveal

Tap card or press Space to flip

See all 13 cards

What are the relative mass and relative charge of a proton?: Relative mass 1, relative charge +1.
What are the relative mass and relative charge of a neutron?: Relative mass 1, relative charge 0.
What are the relative mass and relative charge of an electron?: Relative mass 1/1836 (about 0.0005), relative charge −1.
Define atomic (proton) number.: The number of protons in the nucleus of an atom.
Define mass number.: The total number of protons and neutrons in the nucleus of an atom.
How do you calculate the number of neutrons in an atom?: Mass number − atomic number.
Why does a neutral atom have no overall charge?: It has equal numbers of protons (+1) and electrons (−1), so the charges cancel.
How many protons, neutrons and electrons are in ²⁷Al³⁺ (Z = 13)?: 13 protons, 14 neutrons and 10 electrons (three electrons lost).
How many electrons are in ⁸¹Br⁻ (Z = 35)?: 36 electrons (one electron gained).
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 electronic configuration.
Why do isotopes differ in some physical properties?: They have different numbers of neutrons, so different masses; properties such as density and rate of diffusion depend on mass.
Where is most of the mass of an atom found, and why?: In the nucleus, because protons and neutrons each have relative mass 1 whereas electrons have a negligible mass.

Exam questions on Atomic structure and isotopes

A thyroid clinic uses iodine-131, a radioactive isotope, to treat an overactive thyroid gland. Naturally occurring iodine is entirely stable iodine-127. Iodine has atomic number 53.
Explain why iodine-131 and iodine-127 have the same chemical properties but different masses.2 marks
A physics demonstration passes separate beams of protons, neutrons and electrons between two electrically charged metal plates. The beams are deflected by different amounts, or not at all.
Explain why a neutral atom has no overall charge, and why almost all of its mass is in the nucleus.2 marks
Magnesium (atomic number 12) occurs naturally as three isotopes: ²⁴Mg, ²⁵Mg and ²⁶Mg.
Explain what is meant by the term isotopes, using ²⁴Mg and ²⁶Mg as examples.3 marks

See the full worksheet

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).