C1.2 Atomic structure Flashcards
What is a molecule?
Two or more atoms joined by attractive forces called CHEMICAL BONDS
Size of an atom:
given by atomic radius
Typically around 10^-10
Size of bond length:
Distance between the centres of two joined atoms
Typically 10^-10
What 3 subatomic particles are inside of an atom?
Proton
Neutron
Electron
What is the radius of a nucleus?
Approx 100,000x less than radius of an atom
Mass and charges of the subatomic particles:
Proton: 1 , +1
Neutron: 1 , 0
Electron: 0.0005 , -1
What does the chemical symbol show?
atomic Number - amount of protons in the nucleus
Atomic Mass - Total number of protons and neutrons
What is an isotope?
Same element with different number of neutrons
Same atomic number but different atomic mass
What is an ion?
Charge particles formed when atoms lose or gain electrons.
What is Daltons Model - The Billiard Ball?
Atoms are solid spheres
Atoms of a given element are the same
Atoms of different elements are different to each other
What research did Dalton do?
No experiments to investigate atoms
Therefore he had no evidence to support his ideas
What is Thompsons Model - The Plumb Pudding?
An atom is a solid sphere of positive charge
Electrons are tiny, neg charged particles embedded in the atom
Atoms have no net charge because total positive charges in the atom cancel out the total neg charges
What did Thompson do?
Placed electrodes in glass tubes
Applied a high voltage across the electrodes
Produced cathode rays
Problem with Thompsons Model
Geiger & Marsden’s gold foil experiment obtained results that Thompson’s model could not explain
As a result the atomic model had to be revised
What did Rutherford do?
His pupils Geiger and Marsden fired pos-charged Alpha particles at gold foil
A Zinc Sulfide screen was placed around the foil to detect where the particles would end up
Results of Rutherford’s experiment
Most alpha particles went straight through
Rest of alpha particles either went through the foil and deflected at large angles or bounced off the foil
What was Rutherford’s Model of the atom? - the planetary/nuclear model
The atom is mostly empty space
Containing a concentration of mass in the centre
the centre must be pos charged
With electrons randomly orbiting the nucleus like planets around a sun
Problems with Rutherford’s model
Bohr went over his data and did calculations:
If Rutherford’s was true, the electrons should eventually crash into the nucleus because the pos charge of the nucleus would attract the neg charged electrons
What was Bohr’s Model? - The orbital model
The atom is mostly empty space
Containing a concentration of mass in the centre
the centre must be pos charged
With electrons orbiting the nucleus on fixed electron shells
To be on a certain shell, an electron had to have a certain amount of energy
DaTe RnBo
Dalton, atom
Thompson, electron
Rutherford, nucleus
Bohr, orbitals
