Chemistry test 2025

31/3/2025

Alpha radiation properties

Composed of (α) alpha particles (two protons and neutrons), positive charge (+2), low penetrating power with a strong ionizing power.

Beta radiation properties

Composed of (β) beta particles (electrons) with a negative charge (-1), a medium penetrating power, and a medium ionizing power.

Gamma radiation propertis

Composed of high-energy radiation (photons) with no charge, a high penetrating power, and a very weak ionizing power.

Democritus’ discovery

All substances are made up of atoms

John Dalton

Atoms are solid spheres and cannot be divided
Atoms of different atoms combine to form compounds

JJ thompson

Discovered electrons.

Made the plum pudding model. An atom is a positively charged sphere with negatively charged particles (electrons) embedded on it

Ernest Rutherford

Nuclei are made up of positively charged particles called protons

Most of the space in an atom is empty

Niels Bohr

Electrons are distributed in energy shells. Use magic numbers to distribute electrons in energy shells in an atom.

Molecule

When two or more atoms join together.

Nucleus

The core of an atom, where most of the mass is located, containing protons and neutrons.

Element

A pure substance with its own properties

Atoms

Atoms are the basic building blocks of everything around us, which are indivisible.

Ionise

To add or remove an electron from an atom, making it electrically charged

Compound

Two or more seperate elements; a mixture

Radio isotope

A radioactive isotope is an unstable form of an element that emits radiation to transform into a more stable form. (Decay)

Electron shell

A specific energy level or area around the nucleus where electrons are likely to be found.
(look like rings)

Half life

The time it takes for half of a radioactive element to decay. (carbon-14)

Isotopes

Atoms of the same element that have the same number of protons but a different number of neutrons.

Ionising radiation

Energy or matter that knocks electrons off atoms. (like DNA breaking)

Atomic number

The number of protons in the nucleus of an atom.

Isotope Uranium-238 and their use

Used in nuclear power plants and weapons.

Isotope Carbon-14 and their use

Used to determine the age of ancient materials.

What is the neutron formula?

Mass number - Atomic number = Neutrons

What is the proton formula?

Atomic number = Protons

What is the electron formula?

Atomic number = Electron

What is the mass number formula?

Proton + Neutron = Mass number