The Atom Flashcards
What is matter?
the scientific name for materials
What is meant by the particulate nature of matter?
all matter is made up of tiny particles-atoms,moleucules and ions
Name the 3 states of matter
solid, liquid,gas
What is the motion of a solid?
particles vibrates around a fixed point
What is the motion of a liquid?
particles slide over eachother
What is the motion of a gas?
particles are completely free in movement and will spread by diffusion to fill the container they are in
What are the properties of a solid?
- fixed volume
- fixed shape
- cannot flow
- cannot be compressed
What are the properties of a liquid?
- no fixed shaped
- fixed volume
- can flow
- cannot be compressed
What are the properties of a gas?
- no fixed shaped
- no fixed volume
- cannot be compressed
- can flow
What is the evidence for the existence of small particles?
-put ammonia and hydrogen chloride soaked in cotton wool in a gas tube. a white cloud of ammonium chloride will form as they spread out by diffusion and meet
What is diffusion?
the spontaneous spreading out of a substance due to the natural movement of its particles
Who were the first to propose the idea of an atom?
greek philosophers
State 2 assumptions of John daltons atomic theory
- all matter is made up of tiny particles called atoms
- atoms are indivisible. they cannot be broken down into simpler particles
What is a vacuums tube?
it is a glass tube use to passed an electric current through air at a low presser
Why is the ammonia chloride closer to HCL?
ammonia’s particles move quicker than hydrogen chloride gas’
Describe the contribution of William crooks discovery of the electron
- he place a negative electrode called a cathode at one end of the tube and placed a positive electrode , an anode . this was a Maltese cross in the middle of the vacuums tube
- when he switched on the current the tube glowed/floureced and a shadow of the cross was seen at the end of the tube
- when he put a pedal wheelmounted on a rail in front of the cathode and turned on the current it moved from the cathode to the anode
What did William Crookes conclude from his experiment?
-invisable rays called cathode rays travelled in straight lines from the cathode to the anode (the shadow was sharp)
-invisable rays caused the tube to flourense when they struck the side of the tube
cathode rays had enough energy to move a pedal wheel
Describe the contribution of JJ Thomson tot he discovery of the electron
- he obtain a narrow beam cathode rays by passing them through a hole in the anode.
- the ray of cathode rays passed between two metal plates
- when there was no charge on the plates the cathode rays traveled in a striaght light and struck the screen at the end creating a dot of light
- when a positive charge was placed on the top metal plate the dot on the screen move upwards
- from this jjthomson concluding that cathode rays were streams of negatively charged particles called electrons as they were attracted by the positive charge
Describe the contribution of geoegre stoney
was the first to propose the smallest amount of electric charge would be called an electron
Describe the e/m of the electron
jjthomson also found out that cathode rays were deflected in a magnetic field
- from this experiment he calculated the ratio of charge of the electron (e) to mass of the electron (m)
- this was called the e/m of the electron
Who found the e/m of the electron?
jjhonson
What are cathode rays?
streams of negatively charged particles called electrons
Describe the contributation of Robert Milikan
milkman used oil droplets to calculate the size of the charge of the electron. from this he subbed his value into the e/m of the electron and found its mass.
What are the properties of cathode rays?
- travel in straight lines from the cathode to the anode
- have enough energy to move a paddle wheel
- deflected by an electric field
Describe JJThomsons plum pudding model of the atom
atom is a ball of positive charge with electrons embedded in it at random like raisons in a pudding. seeing as an atom is neutral it must of had some positive charge to neutralise the negatively charged electrons
Draw the structure of JJThomson atom
electrons embedded at random
sphere of positive charge
Describe the discovery of the nucleus
rutherford, geiger and marsden studied the scattering of alpha particle by very thin sheet of gold foil
- they bombarded alpha particles at very thin sheet of gold foil with a flourensent screen at the other side of it.
- they expected most to a particles to go right through and some to be deflected at small angles when they meet a positive charge
- most went right through as they did not come into contact with the nucleus
- somewere deflected at large angles as they came near the nucleus
- some were reflected back along their own path as they came directly in contact (collided) with the nucleus
-conclusion; the positive charge and mass of the atoms of the gold foil were condensed into a small dense core called the nucleus. the rest of the atom was empty space where the electrons were
Which 3 scientist discovered the nucleus?
rutherford geiger and marsden
Describe the discovery of the proton
rutherford started bombarding alpha particles at other atoms. when they were bombarded into lighter atoms light like oxygen and nitrogen it broke up the nuclei to release positively charged particles called protons
Draw the structure of the atom described by Rutherford
protons of atom in nucleus with cloud of electrons surrounding it
Describe the discovery of the neutron
Chadwick bombarded a particles at beryllium which broke up the nuclei to release neutral particles called neutrons
Recall the properties of the sub-atomic particles
PROTON relative charge +1 relative mass 1 location nucleus NEUTRON relative charge 0 relative mass 1 location nucleus ELECTRON relative charge -1 relative mass 1/1838 location outside the nucleus
What are alpha particles?
positively charged particles consisting of 2 neutrons and 2 protons produced by certain radioactive substances.
