Chapter 2: The Atom Flashcards
What is the specific name for materials?
-matter
What is matter?
-the specific name for materials
The idea that materials are made up of particles is often referred to as what?
-particulate nature of matter
What is particulate nature of matter?
-the idea that materials are made up of particles
What is the spreading of gases called?
-diffusion
What is diffusion?
-the spreading of gases
When can diffusion in a liquid be seen?
2
- if a large crystal of copper sulphate is placed at the bottom of a large graduated cylinder filled with water
- after a few hours the blue colour will have spread throughout the water
Who were the first to propose that matter was composed of small particles?
-Greek philosophers
Greek philosophers were the first to propose what?
-that matter was composed of small particles
Who was the most important of the Greek Philosophers who proposed matter was composed of small particles?
-Democritus
Who was Democritus?
-he was the most important of the Greek Philosophers who proposed matter was composed of small particles
What did the Greek philosophers believe?
-they believed that the tiny particles of which all matter was composed were so small that they could not be broken down into even smaller particles
Who believed that the tiny particles of which all matter was composed were so small that they could not be broken down into even smaller particles?
-Greek philosophers
Where does the word atom come from?
-the Greek word atomos meaning invisible
What word comes from the Greek atomos?
-atom
Who wrote a book in which he put forward an Atomic Theory to explain the results of a number of experiments he had performed with gases?
-John Dalton
What did John Dalton put forward in a book?
-an Atomic Theory
Why did John Dalton put forward an Atomic Theory?
-to explain the results of a number of experiments he had performed with gases
Who was John Dalton?
-he was an English chemist
Who was William Crookes?
-he was an English chemist
What experiment did William Crookes carry out?
-he carried out an experiment to investigate what happens when an electric current is passed through a glass tube containing air at low pressures
Who carried out an experiment to investigate what happens when an electric current is passed through a glass tube containing air at low pressures?
-William Crookes
What is contained in the glass tube during William Crookes’ experiment?
-air at low pressure
What contains the air at low pressure during William Crookes’ experiment?
-a glass tube
What is passed through the glass tube containing air at low pressures during William Crookes’ experiment?
-electric current
What is the electric current passed through during William Crookes’ experiment?
-a glass tube containing air at low pressures
What is the type of glass tube commonly called in William Crookes’ experiment in cathode rays called?
-vacuum tube
Who used a vacuum tube during their experiments?
-William Crookes
What is a vacuum tube?
-a type of glass tube
What did Crookes find was coming from the metal plate inside the tube connected to the negative end of the power supply?
-radiation
Where did Crookes find radiation was coming from during his experiment?
-the metal plate inside the tube connected to the negative end of the power supply
What was the metal plate inside the tube where Crookes found radiation was coming from connected to?
-the negative end of the power supply
What is the negative end of the power supply connected to in Crookes experiment?
-the metal plate inside the tube
How did Crookes show the existence of radiation?
-by placing a Maltese cross inside the tube
What did Crookes prove the existence of by placing a Maltese cross inside the tube?
-radiation
What type of cross did Crookes place inside the vacuum tube?
-a Maltese cross
Where did Crookes place the Maltese cross during his experiment?
-inside the vacuum tube
What did Crookes find happened after the Maltese cross was placed inside the vacuum tube of his experiment?
-he found that a shadow of the Maltese cross was formed at the other end of the tube
What shadow was formed at the other end of the vacuum tube of Crookes’ experiment?
-a shadow of the Maltese cross
Where was the shadow of the Maltese cross formed in Crookes’ experiment?
-at the other end of the tube
What name did Crookes use to describe the rays coming form the cathode?
-cathode rays
What did Crookes call cathode rays?
-the rays coming from the cathode in his experiment
What happens when cathode rays strike the glass of a vacuum tube?
-they cause the glass to glow or fluoresce
What is the shadow of the Maltese caused by?
-it is caused when the cathode rays are stopped by the Maltese cross
Why did Crookes carry out a second experiment?
-to investigate the properties of cathode rays
What did Crookes investigate the properties of during his second experiment?
-the properties of cathode rays
What did Crookes place on mounted rails, in front of the cathode during his second experiment?
-a light paddle wheel
Where did Crookes place the light paddle wheel during his second experiment?
-on mounted rails, in front of the cathode
What happened when the current was switched on during Crookes’ experiment?
-the paddle wheel rotated and travelled down the tube
When did the paddle wheel rotate and travel down the tube during Crookes’ second experiment?
-when the current was switched on
What did Crookes observe happened to the vanes in his second experiment?
-they always turned away from the cathode
What always turned away from the cathode in Crookes’ experiment?
-the vanes
What did Crookes’ conclude from the vanes always turning away from the cathode?
-he concluded that these vanes were being struck by particles coming from the cathode
What did the particles coming from the cathode strike in Crookes’ second experiment?
-the vanes
What were the properties of cathode rays that Crookes was able to deduce from his two experiments?
(3)
- cathode rays travel in straight lines
- cathode rays cause glass to fluoresce when they strike it
- cathode rays possess enough energy to move a paddle wheel
In what way do cathode rays travel?
-in straight lines
What rays travel in straight lines?
-cathode rays
How did Crookes deduce that cathode rays travel in straight lines?
-since the shadow of the Maltese cross was sharp
What do cathode rays cause glass to do?
-fluoresce when they strike it
When does glass fluoresce?
-when cathode rays strike it
What do cathode rays possess enough energy to move?
-a paddle wheel
What rays possess enough energy to move a paddle wheel?
-cathode rays
Where was J.J Thomson working?
-Cavendish Laboratory at Cambridge University
What famous English scientist worked at Cavendish Laboratory at Cambridge University?
-J.J Thomson
What did J.J Thomson devise an experiment to investigate?
-if the cathode rays discovered by Crookes consisted of charged particles
Who devised an experiment to investigate if the cathode rays discovered by Crookes consisted of charged particles?
-J.J Thomson
How did J.J Thomson obtain a narrow beam of cathode rays?
-by passing them through a small hole in the positive electrode
Why did J.J Thomson pass the cathode rays through a small hole in the positive electrode in his experiment?
-to obtain a narrow beam of cathode rays
What did J.J Thomson pass through a small hole in the positive electrode?
-a narrow beam of cathode rays
What did J.J Thomson put a hole in during his experiment?
-the positive electrode
What did J.J Thomson do to the positive electrode in his experiment?
-he put a small hole in it
What does the narrow beam of cathode rays pass between in J.J Thompsons’ experiment?
-two parallel metal plates
What is passed between two parallel metal plates in J.J Thompson?
-the narrow beam of cathode rays
Where are the two parallel metal plates located in J.J Thompsons’ experiment?
-half way along the tube
What was located half way along the tube in J.J Thompsons’ experiment?
-the two parallel metal plates
What happened to the narrow beam of cathode rays after it passed through the two parallel metal plates in J.J Thompsons’ experiment?
-they then struck a fluorescent screen at the far end of the tube
What was located at the far end of the tube in J.J Thompsons’ experiment?
-a fluorescent screen
Where was the fluorescent screen located in J.J Thompsons’ experiment?
-at the far end of the tube
What struck a fluorescent screen at the far end of the tube in J.J Thompsons’ experiment?
-a narrow beam of cathode rays
What happened to the fluorescent screen when it was struck by the narrow beam of electrons in J.J Thompsons experiment?
-it glowed
What did J.J Thompson found happened if there was no charge on the parallel plates during his experiment?
-the beam of cathode rays passed straight down the tube and struck the fluorescent screen
When did the cathode rays pass straight down the tube and strike the fluorescent screen in J.J Thompsons’ experiment?
-when there was no charge on the parallel plates
What happens when a positive charge was put on the top plate in J.J Thompsons’ experiment?
-the spot where the fluorescent screen was struck moved upwards
When did the spot where the fluorescent screen was struck move upwards in J.J Thompsons’ experiment?
-when a positive charge was put on the top plate
What did Thomson conclude when the cathode rays were attracted up towards the positive plate in his experiment?
-that they consisted of negatively charged particles
Why did J.J Thompson conclude that the cathode rays consisted of negatively charged particles?
-as they were attracted up towards the positive plate and unlike charges always attract each other
What is the name given to negatively charged particles?
-electrons
What are electrons?
-the name given to negatively charged particles
Who is recognised as the person who discovered the electron?
-J.J Thompson
What is J.J Thompson recognised for discovering?
-the electron
In J.J Thompsons’ second experiment where did he place the large electromagnet?
-outside the glass tube
What was placed outside the glass tube in J.J Thompsons’ second experiment?
-a large electromagnet
What did J.J Thompson do to the magnetic field in his second experiment?
-he adjusted the strength of it
What did J.J Thompson adjust the strength of in his second experiment?
-the magnetic field
What did J.J Thompson find happened to the electrons in his second experiment?
-he found they were deflected by the magnetic field
What was deflected by the magnetic field in J.J Thompsons’ second experiment?
-electrons
What was J.J Thompson able to do to the electrons using the magnetic field in his second experiment?
-he was able to bring the beam of electrons back down to its original position
From the results of his second experiment what was J.J Thompson able to calculate?
-the ratio of the charge of the electron to its mass
How did J.J Thompson calculate the ratio of the charge of the electron to its mass?
-from the results of his second experiment
What was J.J Thompson not able to calculate from his second experiment?
-he was not able to measure separately either the quantity of negative charge on the electron or the mass of the electron
Who was able to measure the ratio of the charge of the electron to its mass?
-J.J Thompson
Who set up an experiment to determine the size of the charge on the electron?
-Robert Millikan
What did Robert Millikan determine?
-the size of the charge on the electron
Who was Robert Millikan?
-an American physicist
In Robert Millikan’s experiment what was sprayed between two charged metal plates?
-tiny droplets of oil
In Robert Millikan’s experiment where were the tiny droplets of oil sprayed?
-between two charged metal plates
What did Millikan use to ionise the air between the plates?
-x rays
What did Millikan use x-rays for in his experiment?
-to ionise the air between the plates
What happens to the molecules in the air when they are ionised in Millikan’s experiment?
-they lose electrons and forms ions
What did the oil droplets pick up as they fell through the air in Robert Millikan’s experiment?
-electrons which came from the molecules in the air when they were ionised
What picked up the electrons which were lost by the molecules in the air when they were ionised during Millikan’s experiment?
-oil droplets
What happened to the oil droplets after they picked up the electrons which were lost by the molecules in the air when they were ionised during Millikan’s experiment?
-they became negatively charged
Why did the oil droplets become negatively charged in Millikan’s experiment?
-they had picked up electrons
What did Millikan do to observe the oil droplet when he placed a positive charge on the top plate during his experiment?
-he used a microscope to focus on a particular oil droplet as it fell through the air
What did Millikan observed through a microscope focus on an oil droplet falling through the air when a positive charge was placed on the top plate during his experiment?
-the negatively charged oil droplet was attracted up towards the positive plate
What did Millikan adjust the charge of during his experiment?
-the positive charge of the top plate
Until what occurred did Millikan adjust the positive charge on the top plate during his experiment?
-until the oil droplet was stationary
From various measurements that Millikan took what was he able to calculate?
-the size of the charge on the electron
How was Millikan able to calculate the size of the charge on the electron?
-from various measurements
Who was able to calculate the size of the charge on an electron?
-Robert Millikan
What did Millikan calculate the mass of?
-the electron
What did Millikan calculate of an electron?
-its mass
What did J.J Thompson propose in 1898?
-a very simple model of the structure of an atom
Who proposed a very simple model of the structure of an atom in 1898?
-J.J Thompson
Summarise J.J Thompson’s model of the structure of an atom?
2
- an atom is like a sphere of positive charge
- electrons are embedded in the sphere at random
In J.J Thompson’s model of the structure of an atom what did he say an atom was like?
-a sphere of positive charge
In J.J Thompson’s model of the structure of an atom what did he saw was like a sphere of positive charge?
-an atom
In J.J Thompson’s model of the structure of an atom what type of charge did he say an atom was like a sphere of?
-positive charge
In J.J Thompson’s model of the structure of an atom what did he say was embedded in the atom at random?
-electrons
In J.J Thompson’s model of the structure of an atom where did he say electrons were embedded?
-in the atom at random
What did J.J Thompson’s model of the structure of an atom become known as?
-the ‘Plum Pudding’ model
Why did J.J Thompson’s model of the structure of an atom become known as the ‘Plum Pudding’ model?
-it was something like a pudding with raisins in it
What did J.J Thompson’s model explain?
-why atoms were neutral
Who was Ernest Rutherford?
-a scientist from New Zealand
Who was a scientist from New Zealand who studied the scattering of particles called alpha particles?
-Ernest Rutherford
Who studied the scattering of alpha particles by a very thin sheet of gold foil?
-Ernest Rutherford
What did Ernest Rutherford study?
-the scattering of alpha particles by a very thin sheet of gold foil
What did Ernest Rutherford use to scatter aloha particles?
-a very thin sheet of gold foil
What did Rutherford use a very thin sheet of gold foil to do?
-scatter alpha particles
What are alpha particles?
-positively charged particles produced by certain radioactive substances
What are positively charged particles produced by certain radioactive substances?
-alpha particles
What are alpha particles produced by?
-certain radioactive substances
What are produced by certain radioactive substances?
-alpha particles
What did Rutherford bombard with alpha particles in his experiment?
-a thin piece of gold foil
What did Rutherford do to the thin piece of gold foil in his experiment?
-bombard it with alpha particles
What do alpha particles consist of?
-groups of two neutrons and two protons stuck together
What consist of groups of two neutrons and two protons stuck together?
-alpha particles
What did Rutherford use to detect the alpha particles in his experiment?
-a phosphorescent screen made of zinc sulphide to detect alpha particles
What did Rutherford use a phosphorescent screen made of zinc sulphide for in his experiment?
-to detect alpha particles
What was the phosphorescent screen that Rutherford used to detect alpha particles made of?
-zinc sulphide
What was made of zinc sulphide and used to detect alpha particles in Rutherford’s experiment?
-a phosphorescent screen
What happens when an alpha particle strikes a phosphorescent screen?
-a little flash of light appears on the screen
What did Rutherford use to observe the flashes of light which appeared on the phosphorescent screen during his experiment?
-a microscope
What did Rutherford use a microscope to observe during his experiment?
-the flashes of light which appeared on the screen when struck by alpha particles
What did Rutherford find happened to some alpha particles during his experiment?
(2)
- they were deflected at large angles as they passed through the gold foil
- some were deflected back along their own path
What did Rutherford conclude from his experiment?
-that the positive charge and the mass of the atoms of the metal foil were concentrated in a small dense core called the nucleus of the atom
Where did Rutherford say the positive charge and the mass of the atoms of the metal foil were concentrated in?
-a small dense core called the nucleus of the atom
What did Rutherford say was concentrated in a small dense core called the nucleus of the atom?
-the positive charge and the mass of the atoms of the metal foil
Who is responsible for the discovery of the nucleus?
-Ernest Rutherford
What is Ernest Rutherford responsible for the discovery of?
-the nucleus
What does the positively charged alpha particles repel in Rutherford’s experiment?
-the positively charged nucleus
What does the positively charged nucleus repel in Rutherford’s experiment?
-the positively charged alpha particles
When were the alpha particles deflected along their original paths during Rutherford’s experiment?
-when they collided head on with the nucleus
What happened when the alpha particles collided head on with the nucleus during Rutherford’s experiment?
-they were deflected along their original paths
What caused the alpha particles to be deflected at large angles during Rutherford’s experiment?
-it was caused by the alpha particles coming very close to the high concentration of positive charge in the nucleus and being repelled by this high concentration of positive charge
What happens when alpha particles come close to the high concentration of positive charge in the nucleus of gold atoms in Rutherford’s experiment?
-they are repelled by this high concentration of positive charge causing them to be deflected at large angles
Why were only a small number of alpha particles reflected back along their original paths during Rutherford’s experiment?
-because the positive charge and the mass of the atoms of the metal foil were concentrated in such a small dense core (nucleus)
What three observations did Rutherford make from his experiment?
(3)
- most alpha particles pass straight through the gold foil
- some alpha particles are deflected at large angles
- a small number of alpha particles are reflected back along their own paths
What three conclusions did Rutherford make from his experiment?
(3)
- most of the atom is empty space
- the alpha particles are repelled when they pass near the small positive nucleus
- a small number of alpha particles collide head on with the nucleus
What did Rutherford conclude from his observation that most alpha particles pass straight through the gold foil?
-most of the atom is empty space
What did Rutherford observe to conclude that most of the atom is empty space?
-most alpha particles pass straight through the gold foil
What did Rutherford conclude from his observation that some alpha particles are deflected at large angles?
-the alpha particles are repelled when they pass near the small positive nucleus
What did Rutherford observe to conclude that the alpha particles are repelled when they pass near the small positive nucleus?
-some alpha particles are deflected at large angles
What did Rutherford conclude from his observation that a small number of alpha particles are reflected back along their own paths?
-a small number of alpha particles collide head on with the nucleus
What did Rutherford observe to conclude that a small number of alpha particles collide head on with the nucleus?
-a small number of alpha particles are reflected back along their own paths
What did Rutherford find when he bombarded light atoms such as oxygen and nitrogen with alpha particles?
-small positively charged particles were given off
What were small positively charged particles given off in Rutherford’s experiments?
-light atoms such as oxygen and nitrogen that had been bombarded with alpha particles
With what elements were positively charged particles not given off when bombarded with alpha particles during Rutherford’s experiments?
-heavier metals such as gold
How did Rutherford explain why positively charged particles were given off of light atoms such as oxygen and nitrogen when bombarded with alpha particles?
-the alpha particles were breaking up the nuclei of the lighter atoms to release positively charged particles
Why were positively charged particles not given off of heavier atoms when bombarded with alpha particles?
-the large positive nuclear charge repelled the alpha particles before they had a chance to break up the nucleus
What did Rutherford call the positively charged particles which were given of by light atoms when bombarded by alpha particles?
-protons
Summarise Rutherford’s work
3
- he discovered that the atom consists of a small dense positive core called the nucleus
- he discovered that positive particles called protons were located in the nucleus
- the new structure of the atom proposed by Rutherford was that it consisted of a nucleus and that the electrons were in some sort of ‘electron cloud’ surrounding the nucleus
What did Rutherford propose the structure of an atom was?
-it consisted of a nucleus and that the electrons were in some sort of ‘electron cloud’ surrounding the nucleus
Who is responsible for the discovery of the neutron?
-James Chadwick
What is James Chadwick responsible for the discovery of?
-the neutron
What did James Chadwick bombard a sample of with alpha particles during his experiment?
-a sample of beryllium
What did James Chadwick bombard a sample of beryllium with during his experiment?
-alpha particles
What did Chadwick discover came from the beryllium during his experiment?
-some type of radiation consisting of particles with no charge
What did Chadwick discover some type of radiation consisting of particles with no charge was coming from during his experiment?
-the sample of beryllium bombarded with alpha particles
Why were these particles coming from the beryllium in Chadwick’s experiment difficult to detect?
-they were neutral
What did Chadwick discover about the neutral particles radiating from the beryllium sample during his experiment?
-they were penetrating enough to knock protons out of paraffin was
What did Chadwick discover the neutral particles radiating from the beryllium sample were penetrating enough to do during his experiment?
-knock protons out of paraffin wax
What did Chadwick discover the neutral particles radiating from the beryllium sample were penetrating enough to knock protons from during his experiment?
-paraffin wax
What did Chadwick discover the neutral particles radiating from the beryllium sample were penetrating enough to knock what from paraffin wax during his experiment?
-protons
What did Chadwick conclude the alpha particles were knocking out of the nucleus of the beryllium atom during his experiment?
-neutral particles
What did Chadwick conclude were knocking neutral particles out of the nucleus of the beryllium atom during his experiment?
-alpha particles
What did Chadwick conclude the alpha particles were knocking neutral particles out of the what of the beryllium atom during his experiment?
-the nucleus
What did Chadwick conclude the alpha particles were knocking neutral particles out of the nucleus of during his experiment?
-beryllium atoms
What did Chadwick find the neutral particles discovered in his experiments had about the same mass?
-the proton
What did Chadwick discover had about the same mass as a proton?
-the neutral particles discovered in his experiments
What were neutrons subsequently used to bring about?
-the splitting of atoms of uranium to release nuclear energy in the atomic bomb and in nuclear reactors
What were subsequently used to bring about the splitting of atoms of uranium to release nuclear energy in the atomic bomb and in nuclear reactors?
-neutrons
What would happen if only protons existed in the nucleus?
-it would fall apart
Why would the nucleus of an atom fall apart if it only consisted of protons?
-because of the repulsive forces of the protons for each other
What do neutrons help to do to protons in the nucleus?
-‘cement’ the positively charged protons together
What are the three sub-atomic particles?
3
- protons
- neutrons
- electrons
What does sub-atomic mean?
-inside the atom
What word means ‘inside the atom’?
-sub-atomic
What two particles are found inside the nucleus?
2
- protons
- neutrons
What particles are located somewhere in the space outside the nucleus?
-electrons
What is the relative charge of a proton?
- +1
What sub-atomic particle has a relative charge of +1?
-proton
What is the relative charge of a neutron?
- 0
What sub-atomic particle has a relative charge of 0?
-neutron
What is the relative charge of an electron?
- -1
What subatomic particle has a relative charge of -1?
-electron
What is the relative mass of a proton?
- 1
What is the relative mass of a neutron?
- 1
What sub-atomic particles have a relative mass of 1?
2
- proton
- neutron
What is the relative mass of an electron?
- 1 divided by 1838
What has a relative mass of 1 divided by 1838?
-electron
Where in an atom is a proton located?
-nucleus
Where in an atom is a neutron located?
-nucleus
What two sub-atomic particles are located in the nucleus?
2
- proton
- nucleus
Where in an atom is an electron located?
-outside the nucleus
What sub-atomic particle is located outside the nucleus?
-electron
