C1-Atomic Structure Flashcards
What is an atom
Atoms are the smallest pieces of an element that can exist.
How many elements have been dicovered
118 and each has its own chemical symbol
What are compounds
Atoms of different elements can be combined together to create compounds. Compounds have formulae that are made by combing the chemical symbols of the elements that make them. Different combinations of atoms result in different compounds. A compound contains at least 2 different elements
What are the key features of a chemical reaction
Compounds are broken up or formed. At least 1 new substance is created. They have a measurable energy change. No atoms are created or destroyed.
What does a chemical equation show
Shows what is happening in a chemical reaction using symbols or words. The reactants (chemicals that are reacting) are on the left hand side, and the products (the chemicals that are forming) are on the right hand size
What are mixtures?
Mixtures are made of 2 or more substances (elements or compounds) that haven’t been chemically combined. Mixtures can be separated. Their chemical properties don’t change because they have been mixed with another substance. Mixtures are common, e.g air is a mixture of gases such as carbon dioxide and oxygen
Explain Chromotography
.Separates solutions with a number of different solutes (solids) in the solvent (liquid)
.Place a drop of the solution to be separated near the bottom of a piece of chromatography paper. Dip the very bottom of the paper into a suitable solvent. The solvent (liquid) moves up the paper and carries the solutes in the solution with it
.Different solutes move at different speeds so they separate on paper
Explain filtration
.Separates mixtures of insoluble solids and liquids
.Done by pouring the mixture through filter paper
-the insoluble solid is trapped
-the liquid runs through the paper and is collected below
Explain crystallisation
Separates solutions into their constituent (different )parts: disolved solids (solutes) and liquid (solvents).
.Heat the mixture so that the solvent evaporates. Eventually crystals ld the solute will form. We can collect the solvent by condensing it as it evaporates
Explain simple distillation
Separates 2 liquids with different different boiling points
.The mixture is heated until the liquid with the lower boiling part starts to boil. The vapour released passes through a condenser where the gas cools back into a liquid
. A thermometer is used to make sure the highest boiling is not exceeded otherwise both liquids would boil and the process would not separate them
Explain fractional distillation
Separates lots of liquids with different boiling points
The mixture is slowly heated until the liquid with the lowest boiling point boils and then condenses
Then the temperature is increased slowly to collect the other fractions through boiling and condensing
Explain Thomson’s plum pudding model
In 1897, an English physicist called J.J Thompson discovered electrons
He modelled the atom as a plum pudding with is a ball of positive charge dough with negatively charged electrons mixed in with the ‘dough’
Explain Rutherford’s nuclear model
.in 1909, Ernest Rutherford discovered that alpha particles could bounce back off atoms. He concluded that an atom’s mass is concentrated in the atom’s centre, this was called the “nucleus” and it contained positively charged particles called protons and negative electrons mixed in
Explain the modern model
Niels Bohr discovered that electrons orbit the nucleus at fixed distances
In 1932 James Chadwick discovered that some particles in the nucleus have no charge at all. He called them neutrons
What is the overall charge of an atom
Atoms have no overall charge as they cancel each other out
