Atoms, Elements, Molecules and

Compounds

Science 1st ESO

By Ainhoa Aporta

Atoms and elements

• Everything is made up of atoms.

• There are over hundred different types of atom. And each type is called an ELEMENT like iron, oxygen or carbon.

A model of an atom

• Atoms themselves are divided into even smaller parts called sub-atomic particles.

Sub-atomic particles• Protons and neutrons are the sub-atomic particles

that make up the nucleus of the atom (the centre).

• Protons have a positiv electric charge

• Neutrons have no electric charge.

● Electrons are the sub-atomic particles that are orbiting around the nucleus. ● They are negatively

charged. That’s way they are attracted by the positive charges in the protons, being held in place.

Atomic number• Atomic number: number of protons in the nucleus of an

atom.

• A normal atom has the same number of electrons as protons. Therefor you can know the number of electrons in an element looking at its atomic number..

Atomic mass• The atomic mass of an atom depends on

the number of protons and neutrons in the nucleus.

Carbon atomic mass = 6 neutrons + 6 protons = 12

Periodic table

• There are 116 known elements, which are organized and classified in the Periodic Table.

• Each element has its own chemical symbol that is used all over the world, for example for Oxygen the chemical symbol is O.

• According to their properties elements can be grouped into:

• Metals

• Non-metals

• Each column contains elements which are similar to each other and is called a group with its number indicated on the top.

• The rows across are called periods.

• http://education.jlab.org/itselemental/ele001.html

• http://www.bbc.co.uk/worldservice/sci_tech/features/elementary/statcon/element2a.shtml

PROPERTIES METALS NON-METALS

Appaerence    

Density    

Conducts

electricity

   

Conducts heat    

Malleable    

Magnetic    

Molecules• Atoms bond together to form larger

particles called MOLECULES, and molecules join together in different ways to produce the matter and the different SUBSTANCES.

Elements and compounds• Those molecules which are made from only

one type of atom are called ELEMENTS.

• Those molecules which are made up of different types of atoms are called COMPOUNDS, such as the molecule of water.

Oxygen (O2), element made up of 2 atoms of oxygen.

Water (H2O), compound made up of 2 atoms of hydrogen and one atom of oxygen.

Investigating compounds

• We can identify which elements are in a compound by flame testing.

• When you burn metallic elements they make flames of different colours.

• Scientists put a sample of the compound on the end of a

wire loop (previously cleaned).

• The wire is then placed in the flame of a Bunsen Burner.

• The flame changes color depending on the element.

Describing molecules- formulae

• When we describe molecules we use formulae.

• When working with formulae:

• We use the chemical symbols to indicate the elements that form the molecule.

• We add numbers to show how many atoms of each element are found in the molecule.

Chemical reactions• Compounds are new substances which get

formed from two or more different elements through a chemical reaction.

• Their properties are different to the properties of the elements that make them.

• Example: hydrogen and oxygen react to form water.

• Rusting is also an example of a combination reaction (oxidation):

• Iron (Fe) + Oxygen (O) iron oxide

• When in the combination reaction only two substances are involved, joining together to form a new compound, the name of the compound will always end in “ide”.

• https://www.youtube.com/watch?v=kRUbVm21L_U

• https://www.youtube.com/watch?v=cJ7rzo1wirs

• https://www.youtube.com/watch?v=FofPjj7v414