History of the atom KO Flashcards
What is the plum pudding model?
Thompson’s theory that suggested atoms were spheres of positive charges with negative electrons stuck in them
What was the structure of Rutherford’s alpha particle scattering experiment?
A circular detector surrounding an alpha source and gold foil.
What were the three observations and conclusions of the alpha scattering experiment?
Most alpha particles passed straight through as the atom is mostly empty space
Some alpha particles were repelled and deflected at large angles as atoms have a nucleus with a large positive charge
Few alpha particles were deflected straight back as the nucleus is small
Rutherford and Bohr’s models can both be referred to as ‘nuclear’ models. Why?
Both models include a positively charged nucleus surrounded by electrons.
What is the difference between Rutherford and Bohr’s models?
Both models include a positively charged nucleus surrounded by electrons.
What did the following scientist find out?
John Dalton
Ernest Rutherford
Niels Bohr
James Chadwick
Atoms are solid spheres and different spheres made up different elements – early 19th century.
Plum pudding model – atoms contain a tiny positive nucleus in the centre where most of the mass is contained, surrounded by a ‘cloud’ of negative electrons – 1909.
He also found out that the nucleus could be divided into smaller particles which have the same charge as a hydrogen nucleus – called them protons – late 1920s.
He stated that the electrons were contained in shells of fixed energies (which would prevent the electrons from being attracted to the nucleus thus causing the atom to collapse.
He found evidence for neutral particles in the nucleus – known as neutrons.
What is the current model of the atom?
A nuclear model: A small positive nucleus containing positive protons and neutral neutrons, surrounded by negative electrons found in fixed shells.
What is the charge and relative mass of a proton
+1 and 1
What is the charge and relative mass of a neutron
0 and 1
What is the charge and relative mass of an electron
-1 and 1/2000
Why do atoms have no overall charge?
They have the same number of positive protons and negative electrons
What is an isotope?
An element with the same number of protons but a different number of neutrons. The atomic number is the same, but the mass number can vary
How are electrons arranged in atoms?
They are arranged in shells (energy levels) surrounding the nucleus. The first shell can hold a maximum of 2 electrons, the second can hold a maximum of 8 electrons and the 3rd shell holds 8 electrons.
Draw a diagram of an atom of Sulfur – labelled fully.
Diagram must show the nucleus, the numbers of protons and neutrons and where they are found, electrons in outer shell must be shown as pairs or bonding electrons as relevant.
What is the electron structure of Argon? (no diagram)
2,8,8.
Why are the elements in group 0 unreactive?
Elements in group 0 have a full outer shell of electrons.
