Atomic structure and the periodic table Flashcards
Define the word ‘element’ in terms of atoms
An element is made up of atoms of the same type
How many elements are shown in the periodic table?
118
What is a compound and how are they represented?
A compound is a substance that contains 2 or more elements that are chemically combined. It is represented using a formula (symbols)
How are compounds formed and separated? What does this involve?
Compounds are formed by chemical reaction in which bonds are formed and an entirely new substance is created.
To separate a compound, energy must be added in the form or heat or electricity.
What are the group 1 & 7 elements known as?
Group 1 elements are known as alkali metals.
Group 7 are known as the halogens.
How do you balance equations?
Use a table
What is a mixture? Are the properties of each substance in the mixture changes or unchanged?
A mixture is 2 or more elements which have not been chemically bonded, meaning the properties of each substance stay the same.
What are the 5 processes which can be used to separate mixtures? (for each process state the mixtures it can be used to seperate)
The 5 processes are:
filtration - insoluble solids from liquids
crystallisation - solids from solutions
simple distillation - a liquid from a solution
fractional distillation- liquids that have different boiling points
chromatography - separate dyes
What is filtration?
The physical process in which solid particles in a liquid or gaseous fluid are removed by the use of a filter medium that permits the fluid to pass through but retains the solid particles.
What is Crystallisation?
A method for transforming a solution into a solid.
What is Chromatography?
A process for separating components of a mixture
What is simple distillation?
It separates a liquid and soluble solids from a solution or a pure liquid from a mixture of liquids
what is fractional distillation?
It is the separation of a mixture into its component parts (fractions)
What lead to a scientific model being changed or replaced?
the data did not agree with their predictions resulting in the model being changed
How did the model of the atom change as new evidence was discovered?
the plum pudding model suggested that the atom was a ball of positive charge with electrons embedded in it the scattering experiment led to a change of the model of the atom being changed as electrons were discovered to orbit the nucleus
What were the roles of Niels Bohr and James Chadwick in the development of the model of the atom?
James identified the neutron.
Niels proposed the theory for the hydrogen atom
Why did the new evidence from the scattering experiment led to a change in the atomic model?
When firing atoms through foil, some particles passed through and some rebounded. This proved that electrons orbited the nucleus.
What are the relative charges of protons, neutrons and electrons?
Protons - +1
Neutrons - 0
Electrons - -1
Why do atoms have no overall electrical charge?
Because they have an equal amount of protons and neutrons
What does atomic number represent?
number of protons in the nucleus of an atom
How do atoms of different elements differ from each other?
by the number of protons
What is the structure of atoms?
Inside the nucleus there are neutrons and protons and orbiting the nucleus there are electrons