Atomic structure&models Flashcards
What two sub atomic particles make up the nucleus?
Protons
Neutrons
What is the relative mass of both protons and neutrons?
1
What is the relative mass of an electron?
1/2000
How do electrons move around the nucleus?
They whizz around on orbitals
What is the mass number?
Total number of protons and neutrons in the nucleus of an atom
What is the atomic number?
The total number of protons, which also tells you the number of electrons
What is an ion?
When an atom loses of gains electrons, an ion is formed.
This causes a positive or negative charge
When forming an ion, how can you tell what the charge of the ion will become?
The group that the element is in will tell you how many electrons it must lose or gain to form a full outer shell
What is an isotope?
A variation of an element with the same number of protons but a different number of neutrons, resulting in a different mass but the same atomic number
Why do isotopes have the same chemical properties?
They have the same configuration of electrons
What was Daltons model of the atom?
He described atoms as solid spheres and said that different spheres made up the different elements
What was Thompsons model of the atom called?
The plum pudding model
What did Thompson conclude from his experiments?
That an atom must contain even smaller, negatively charged particles called electrons
What did the plum pudding model look like?
Electrons surrounded by a positively charged ‘pudding’
In the Rutherford experiment, what did they fire at a thin sheet of gold?
alpha particles
What charge do alpha particles have
positive
What happened to the alpha particles in the Rutherford experiment?
Most of the particles passed straight through the gold atoms and a very small number were deflected backwards
What did Rutherford call his model of the atom?
the nuclear model
What is the design of the nuclear model?
There is a tiny positively charged nucleus at the centre, surrounded by a ‘cloud’ of negative electrons
Most of it is empty space
What were Bohr’s 4 basic principles of the atom?
1) electrons only exist in fixed orbits and not anywhere between
2) each shell has a fixed energy
3) when an electron moves between shells electromagnetic radiation is emitted or absorbed
4) because the energy of shells is fixed, the radiation will have a fixed frequency
Which model do we mainly use today?
Niels Bohr
Whats different about the model we use today and how has it been altered? What is its name?
The model now includes sub-shells
Refined Bohr model
