Atoms Flashcards
Particles
Everything in and around us made up of matter.
Matter consists of small particles that cannot be seen, viz atoms.
Atoms
Atoms are the smallest particles of which all matter consists.
Atoms are made up of different small particles called sub-atomic particles.
Atoms are neutral because the number of electrons (negatively charged particles) is equal to the number of protons (positively charged particles).
Nucleus
The central region of the atom is called the nucleus. It gives an atom mass.
The nucleus is made up of:
• Positively-charged particles called protons;
• Electrically neutral particles called neutrons.
Nucleons are responsible for the mass of the atom.
Proton
Protons are positive particles that are found in the nucleus of the atom.
Electron
Electrons are negative particles that are found around the nucleus of the atom. These are negatively charged particles.
Electrons have a lot of energy and move around the nucleus.
Electrons are attracted to the positive protons in the nucleus. (opposite charges attract each other.)
Electrons are responsible for the volume of the atom.
Neutrons
Neutrons are neutral particles that are found of the nucleus of the atom.
Elements
Elements consist of one kind of atom.
Elements are found on the periodic table.
An element is a substance that cannot be broken down into two or more materials by chemical means.
Some atoms do not occur alone. Two atoms bond to each other to form a molecule. e.g. two oxygen atoms bond to each other to form an oxygen molecule (O2) which is still an element.
All molecules consisting of two identical atoms are called diatomic elements.
There are also diatomic molecules that do not necessarily consist of identical atoms. These molecules are known as diatomic compounds. An example is HCℓ.
Compounds
A compound is a material that consists of atoms of two or more different elements chemically bonded together.
Compounds can be broken down into simpler materials again by heating or electrolysis. The simpler materials are the original elements of which it was made.
Are not found on the periodic table.
Compounds are pure because the particles are all the same. The elements that the bond consists of always bond in the same ratio.
The pieces can only fit together in a certain way.
e.g water, it consists of two hydrogen atoms (H) and an oxygen atom (O) that have bonded together. The formula is H2O
Forces between particles
→ When atoms are close to each other, attractive forces exist between the atoms.
→ The attractive forces keep the atoms together so a compound can form.
→ The attractive forces are very strong.
Attractive forces also exist between molecules. These attractive forces are weak. We only become aware of water vapour when millions of molecules come together to form a drop of water. Sugar is a crystal, but when dissolved we can still taste it.
Repelling forces also exist between particles when it is pushed too close together.
Decomposition
Compounds can be broken down (decomposed) into simpler products.
They can be separated by chemical means.
For a compound to decompose, energy must be added.
A chemical reaction which breaks down a compound into simpler products, is called a decomposition reaction.
Mixtures are separated by physical means (hand sorting, separating funnel, etc.). While compounds can be separated by chemical means.
