The Atom Flashcards
What is the atomic number?
Number of protons = number of electrons
What is the mass number/atomic mass?
Number of protons + number of neutrons
Name the contributors to the atomic model
Dalton Thomson Rutherford Bohr Chadwick
What was John Dalton’s contribution to the atomic model?
- Billiard ball model: an atom is a sold sphere
- An atom cannot be created or destroyed, therefore cannot be divided further
What was Joseph J. Thomson’s contribution to the atomic model?
- Atoms contain oppositely charged particles.
- Electrons (-)
- Protons (+)
- Plum pudding model
What was Ernest Rutherford’s contribution to the atomic model?
The atom consists of a small positive atomic nucleus with electrons orbiting around it
What was Niels Bohr’s contribution to the atomic model?
- Gold foil experiment
- Electrons move around the nucleus in fixed energy levels with particular energies.
What was James Chadwick contribution to the atomic model?
Discovery of the neutron
Describe Rutherford’s atomic model?
- Positively charged atomic nucleus, very small volume.
- Surrounded by an empty space containing negatively charged electrons (electron cloud) of a very small mass, far from the nucleus.
- The electrons move randomly around the nucleus.
Describe Bohr’s atomic model
- Electrons only move around the atomic nucleus in assigned orbits/energy levels.
- Energy level closest to nucleus has the lowest energy .
- An electron can move from one energy level to another
What are isotopes?
Atoms of the same element that have the same atomic number but different atomic masses
How to calculate the average atomic mass
(percentage x isotope) + (percentage x isotope) divided by 100
How do electrons move between energy levels?
By absorbing fixed amounts of energy during the excitation to a higher level or emitting energy with the return to a lower level.
Electron configuration definition
The arrangement of electrons (within the orbitals of energy levels) in an atom.
What are the two types of orbitals
S-orbitals
P-orbitals
Describe s-orbitals
Spherical shape
Nucleus is in the centre
Only one s-orbital per energy level
Describe p-orbitals
- Consists of 2 teardrop-shaped halves
- First energy level doesn’t have any p-orbitals
- Three types of p-orbitals (x, y, z)
Orbital definition
The region in space in which an electron in an atom is usually found.
What do you use to represent orbitals?
Circles or squares
How are electrons represented in orbitals
Arrows
What is the order of filling the orbitals (for electron configuration)?
1s; 2s; 2p; 3s; 3p; 4s
Definition of Valence Electrons
Electrons in the highest energy level.
Can be both s-orbitals and p-orbitals.
Valency
Number of unpaired electrons
How to work out the valency for Groups 1 to 3
= the group number
How to work out the valency for Groups 4 to 8
=8 - group number
No to be confused with finding the ionic charge
What does SP notation stand for?
Spectroscopic notion
What is SP notation?
Used to show the allocation of electrons to the orbitals.
How do you give the Shorthand SP Notation?
Use the preceding noble gas, followed by the configuration of valence electrons in its top energy level .
What is Shorthand SP Notation?
Shorter version of SP notation that uses noble gases.
How to write the electron configuration for positive ions?
When writing the electron configuration you take away one of the electrons.
OR
Use the same electron configuration of the preceding noble gas.
How to write the electron configuration for negative ions?
When writing the electron configuration add an electron.
OR
Use the same electron configuration of the subsequent (same) noble gas.
State Hund’s rule
No pairing in p orbitals before there is not at least one electron in each of them.
State Pauli’s Exclusion Principle
Maximum of two electrons per orbital provided that they spin in opposite directions.
What does Z represent?
Atomic Number (protons=electrons)
What does A represent?
Atomic Mass (protons+neutrons)
