Chemistry Unit 5 Flashcards
Describe the Bohr model
Nucleus orbited by electrons in different energy levels
When did the atomic model start?
in 400 BC
What did Democritus think
he believed that the atom was indivisible and the smallest piece of matter
named it “atomos” - not to be cut
Describe the billard ball model?
Just a ball like structure
Who created the billard ball model?
John dalton in 1804
What was the first atomic theory and who wrote it?
John Dalton wrote it
1) every element is made of atoms
2) he thought atoms of the same element are identical and different from other elements ** incorrect we have isotopes
3) In order to form compounds atoms of different elements combine in whole # ratios
4) In chemical reactions atoms are combine, separated, or rearranged but can never be turned into atoms of a different element
Describe the plum pudding model
Electrons scattered within a positively charged ball
Who created the plum pudding model and when
J.J Thomson in 1897
What did J.J thomson do and what was his atomic theory
JJ thomson experimented with cathode ray tubes and discovered the ELECTRON!
Describe the nuclear model
positively charged nucleus with negative electrons surrounding it
Who discovered the nuclear model and when?
Ernest Rutherford in 1911
What did Ernest Rutherford discover and how?
Through the gold foil experiment (bombarding alpha particles at a thin gold foil) he fouhnd that:
1) atom has mostly empty space
2) most of mass located in the positive NUCLEUS of the atom
3) electrons orbit around nucleus
describe the planetary model
Positive nucleus with protons and neutrons
electrons in specific energy levels can jump between them
Who created the planetary model and when?
niels bohr in 1913
What was niels bohr’s atomic theory
1) electrons exist in distinct orbits
2) electrons cant exist between energy levels
3) electrons can jump to higher orbit when energy is added
4) energy is released when electrons fall to lower orbit
Who discovered the neutron and when?
James Chadwick in 1932
Who came up with the quantum mecanical model?
Schrodinger and heisenberg
What was schrodinger’s atomic theory?
Wave mechanics – the idea that electrons are in clouds and not distinct orbitals
What was heisenbergs atomic theory?
Uncertainty principle – electron location cant be predicted
electrons are both particles and waves
Mass of the three sub atomic particles
P+ and N = mass of 1
E- = mass neglidgable
What is the diamiter of an average atom?
10^-10 m
what is the diamiter of an averge nucleus?
10^-15 m
What is an isotope
They are atoms that have the same # of protons however the number of neutrons differs
How does ratio of neutrons to protons affect nuclear stability
isotopes outside a certain ratio are considered radioactive
how is mass and abundance of each isotope determined?
By using a mass spectrometer
how is average mass # calculated?
(abundence/100 * Relative mass) +(abundence/100 * Relative mass) = average mass
How is energy released when an electron moves from one energy level to the next?
In the form of light
what does schrodinger’s equation determine?
the location of electrons in an atom
Why does looking at an electron change its positiion
The act of looking at it alters its velocity and position
What are the four quantum numbers?
n, l, ml, and m8
What does the quantum number n describe?
Describes the shell (1-7)
The energy level
and the distance from nucleus
example the 1 in 1S shell
what does l describe
Describes the subshell
- the shape and type of orbital
- 4 shapes: s, p, d, f
ex: the S in 1S
what does ml describe
it describes the orbital
- the orientation in space and holds a max of 2 electrons
Ex: subshell S has 1 place for 2 electrons electrons and P has 3 places for 6 electrons
what does m8 describe
describes the electron spin
either counter clockwise or clockwise
What are the three Electron configuration rules?
1) pauli exclusion principle:
- no two e- in same atom can be describe by the same 4 quantum numbers
2) aufbau principle
- when filling orbitals the lowest energy orbitals are filled FIRST
3) Hunds rule
- whe orbitals of equal energy are filled the most stable is the one with the max number of unpaired electrons with the same spin
what is ground state
it is the lowest energy of an electron
what is an orbital?
it is the volume and shape of the place where an electron is likely found
what does the term electron configuration mean?
it is the way that electrons are positioned outside the atom
