Year 9 chemistry topics 1 and 2

What is an isotope?

Atoms of the same element that differ in the number of neutrons.

How do isotopes of the same element compare chemically?

They have the same chemical properties but different masses.

Provide an example of isotopes of carbon.

Carbon-12, Carbon-13, and Carbon-14.

What is the atomic mass of Carbon-12?

12.

What is the atomic mass of Carbon-14?

14.

What is the atomic mass of Carbon-13?

13.

What defines stable atoms?

In stable atoms, protons and neutrons are held together strongly.

What characterizes unstable atoms?

In unstable atoms, protons and neutrons are not held together strongly.

What happens to unstable isotopes?

They decay and emit radiation, becoming radioactive isotopes.

What is natural radioactivity?

Radioactivity emitted from matter without energy being supplied, occurring spontaneously.

What is artificial radioactivity?

Radioactivity created by bombarding isotopes with subatomic particles.

What is nuclear radiation?

The energy emitted by radioactive substances from the nucleus.

Name the three types of nuclear radiation.

Alpha particles, beta particles, and gamma rays.

What is half-life?

The time it takes for half of a sample of a radioactive isotope to decay.

How can decay rates vary?

Decay may occur quickly (microseconds) or over long periods (billions of years).

What is a parent isotope?

The original radioactive isotope before decay.

What is a daughter isotope?

The product of the decay of a parent isotope.

How is the age of a fossil estimated using isotopes?

By calculating the remaining percentage of Carbon-14 and its half-life.

What is the significance of the atomic number?

It identifies an element and is equal to the number of protons.

What is nuclide notation?

A way to represent isotopes, showing the element's symbol, atomic number, and mass number.

Define a radioactive isotope.

An isotope that is unstable and emits radiation as it decays.

What is the difference between alpha and beta particles?

Alpha particles are helium nuclei, while beta particles are high-energy electrons.

What is a stable atom?

An atom with a balanced ratio of protons and neutrons, not undergoing decay.

What is an unstable atom?

An atom with an imbalanced ratio of protons and neutrons, undergoing decay.

What are the three groups of substances that matter can be placed into?

Elements, compounds, and mixtures.

Which group contains substances made up of only one type of atom?

Elements.

What is the difference between a compound and a mixture?

Compounds are elements chemically bound together in a fixed ratio, while mixtures are a blend of substances not chemically bound.

How is an atom different from a molecule?

Atoms are pure substances made up of a single element, while molecules are two or more atoms chemically bound together.

Who first suggested that all substances are made up of particles called atoms?

Democritus, a Greek philosopher, in 400 BC.

What did John Dalton propose about atoms in 1808?

All matter is made of tiny particles called atoms, which cannot be divided, and atoms of the same element are identical.

What model did J.J. Thompson propose in 1897?

That atoms are positively charged spheres with negatively charged electrons embedded in them, like fruit in a plum pudding.

What did Lord Rutherford propose about atomic structure in 1911?

Atoms are mostly empty space, with a dense nucleus containing positively charged protons and electrons orbiting the nucleus.

What modification did Niels Bohr make to Rutherford's model in 1913?

He proposed that electrons travel on different orbitals with different energy levels and do not spiral into the nucleus.

What did Sir James Chadwick discover in 1932?

That the nucleus of an atom contains neutrons, which have no charge and a similar mass to protons.

What is the current model of an atom based on?

The Niels Bohr model, which includes a tiny, dense nucleus surrounded by electrons.

What is the relationship between the number of protons and electrons in an atom?

In a neutral atom, the number of protons equals the number of electrons, resulting in no overall electric charge.

What information does the periodic table provide for each element?

Name, symbol, atomic number, and atomic mass.

What is the atomic number of an element?

The number of protons within the nucleus.

What is the atomic mass of an element?

The total number of protons and neutrons within the nucleus.

What are the atomic elements for Oxygen, Hydrogen, Gold, and Sodium?

Oxygen (O, 8), Hydrogen (H, 1), Gold (Au, 79), Sodium (Na, 11).

Define 'atom'.

The smallest unit of a chemical element, consisting of a nucleus surrounded by electrons.

Define 'electron'.

A subatomic particle with a negative charge that orbits the nucleus of an atom.

Define 'element'.

A pure substance made up of only one type of atom.

Define 'mixture'.

A combination of two or more substances that are not chemically bonded.

Define 'molecule'.

A group of two or more atoms chemically bonded together.

Define 'neutron'.

A subatomic particle found in the nucleus of an atom that has no electric charge.

Define 'nucleus'.

The dense center of an atom, containing protons and neutrons.

Define 'orbital'.

The region around the nucleus of an atom where electrons are likely to be found.

Define 'proton'.

A positively charged subatomic particle found in the nucleus of an atom.

Define 'substance'.

A form of matter that has a definite composition and distinct properties.