The Atom Flashcards
(41 cards)
Heisenberg’s Uncertainty Principle
It’s impossible to measure both the velocity and position of an electron at the same time
An orbital
A region in space where there’s a high probability of finding an electron
Sublevel
A subdivision of a main energy level and consists of one or more orbitals of the same energy
Energy level
The fixed energy value an electron in an atom may have
Ground state of an atom
When the electrons in the atom occupy the lowest available energy levels
Excited state of an atom
When the electrons in the atom occupy higher energy levels than those available in the ground state
Dalton’s Atomic Theory
All matter is made up of tiny particles called atoms. Atoms are indivisible, can’t be broken down into smaller particles
Cathode rays
- Streams of electrons
- That travel in straight lines from the cathode to the anode
- Are deflected by electric/magnetic fields
- Have enough energy to move a paddle wheel
Diffusion?
The spreading of gases
What did Greek philosophers propose about the atom?
Matter is composed of small particles, called atoms
Atoms are indivisible
How did Crookes discover cathode rays?
He passed an electric current through air at a low pressure in a vacuum tube
He showed the rays were coming from the cathode (negative electrode)
The cathode rays cast a shadow of a cross at the other end
Cathode rays causes glass..?
To glow when they strike it
How did Crookes investigate the properties of cathode rays?
Paddle wheel experiment, he put a paddle wheel in front of a cathode
when the current was switched on the wheel spun
Conclusion: the wheel was being struck by particles coming from the cathode
Alpha particles
Groups of 2 protons+ 2 neutrons stuck together
Positively charged
Describe the plum pudding model proposed by JJ Thomson
The atom is like a sphere of positive charge with electrons embedded in the sphere at random
Pros and cons of JJ Thomson’s Plum pudding model?
Pro: explains why atoms are neutral
Con: no experimental evidence
Why are Relative Atomic masses rarely whole numbers?
They’re an average of all an element’s naturally occurring isotopes
How can you detect the presence of cathode rays in a vacuum tube?
The paddle wheel spins (tiny particles strike it)
Glass glows at the other end
Who discovered the electron?
JJ Thomson
3 observations made by Rutherford when he bombarded gold foil with alpha particles…
- some reflected back on their own paths
- Some deflected at large angles
- Most didn’t deflect at all
How did Rutherford prove that alpha particles are small and dense?
Only a small amount of alpha particles were deflected, because only a small amount came into contact with the (+) charged nucleus
Mass number
The sum of protons+neutrons in the nucleus of an atom
Relative Atomic Mass
The average of the mass numbers of all the naturally occurring isotopes of an element, taking their abundances into account and expressed on a scale where the atoms of the carbon-12 isotope have a mass number of 12 units
Heterogenous catalysis
Catalysis where the reactant and the catalyst are in different stages, there’s a boundary between them
