Atomic theory 3 Flashcards
What is an alpha particle (L.C)?
Particle consisting of two protons and tow neutrons
Why did Mendeleev place tellurium before iodine in his periodic table of elements? (L.C)
Chemical properties matched (fitted) better in that order
On the basis of the plum pudding model of atomic structure, what results were expected by Rutherford when thin gold foil was first bombarded with alpha particles in 1909? (L.C)
Alpha particles were expected too pass straight through
How did the actual result of Rutherford’s experiment differ from the expected result? (L.C)
- Some alpha particles were deflected at large angles
- A few alpha particles were reflected along original path
How was the model of atomic structure changed as a result of Rutherford’s experiment? (L.C)
- Atoms are mostly made up of empty space with small nucleus
What was the purpose of Millikan’s oil drop experiment of 1908 to 1913? (L.C)
To measure the magnitude of charge on electron
Describe the plum-pudding model of the atom proposed by Thomson around 1897? (L.C)
Electrons in positive sphere (diagram needed)
Give one way of detecting the presence of cathode rays in a vacuum tube. (L.C)
Coloured light/glow
Name the scientist who around 1897 identified cathode rays as subatomic particles and, using a vacuum tube, measured their charge-to-mass ratio. (L.C)
J.J Thomson
What name was given to the subatomic particle that Thomson identified? (L.C)
Electron
State three observations made by Rutherford’s team when they bombarded gold foil with alpha-particles. (L.C)
- Most alpha particles passed straight through
- Some alpha particles were deflected at large angles
- A few alpha particles were reflected along original path
Explain how Rutherford deduced from his results that the nucleus is positive? (L.C)
Repulsion of positive alpha-particles
Explain how Rutherford deduced from his results that the nucleus is small and dense? (L.C)
Statistical analysis of angles of deflection
Describe the structure of Thomson’s ‘plum pudding’ model. (L.C)
Positively charged sphere with electrons embedded in it
What are alpha particles? (L.C)
Particles containing two protons and two neutrons
Explain why some of the alpha particles were deflected at large angles as they passed through the gold foil.
Repelled when passing near the nucleus
Why were some alpha particles reflected back along their original paths? Why did this only happen to a very small number of alpha particles? (Rutherford’s ‘gold foil’ experiment) (L.C)
Some - Collided with nucleus
Why - Nucleus is very small
Draw a labelled diagram to show the new structure of the atom proposed by Rutherford. (L.C)
- Draw
- Nucleus shown and labelled with one shell of electrons shown and labelled
Give two properties of cathode ray (L.C)
- Negatively charged
- High-speed
- Negligible mass
What was the basis used by Mendeleev in arranging the elements in his periodic table? (L.C)
- When arranging according to increasing atomic weight there is a periodic occurrence of similar elements
Why did Mendeleev leave spaces in his periodic table? (L.C)
So that similar elements were in the same group
Explain why Mendeleev reversed the order of elements required by his periodic law. (L.C)
To suit properties to groups
State three assumptions of Dalton’s atomic theory of 1808. (L.C)
- Small
- Indivisible
- Identical atomic mass for particular element
Name the scientist who about 1897, measured the ratio of charge to mass of the electron, e/m. (L.C)
Thomson
Name the scientist who about 1910, proved that the electrons in an atom reside in an electron cloud surrounding a small dense positive central nucleus. (L.C)
Rutherford
Name the scientist who, about 1911, measured the charge on the electron, e. (L.C)
Millikan
State two differences between Mendeleev’s table and the modern periodic table of elements. (L.C)
- Left gaps for undiscovered elements
- Reversed some pairs of elements
Name the scientists who used charged oil drops to determine the size of the charge on a sub-atomic particle, and name the sub-atomic particle. (L.C)
- Robert Millikan
- Electron
What two contributions did Henry Mosely make to the systematic arrangement of the element in the periodic table? (L.C)
- Atomic number
- Characteristic positive charge for element
Describe the model of atomic structure which existed immediately prior to Rutherford’s ‘gold foil’ experiment. (L.C)
Positively charged sphere with electrons embedded at random (diagram required for full marks)
In Rutherford’s experiment it was observed that most of the alpha particles went straight through the gold foil. Two other observations were made. State these two observations and explain how each helped Rutherford deduce that the atom has a nucleus. (L.C)
1st observation : deflection of alpha particles
2nd observation : alpha particles reflected
Explain 1st : particles passed close to small, positive mass
Explain 2nd : particles collided with small, very dense mass
Name the scientist who identified cathode rays as subatomic particles (L.C)
J.J Thomson
What contribution did Newlands make to the systematic arrangement of the elements known to him? (L.C)
- Identified periodicity of properties
- Arranged in increasing relative atomic mass
What contribution did Dobereiner make to the systematic arrangement of the elements? (L.C)
- Triads
- Grouped elements of similar properties in groups of three
Name the scientist who identified cathode rays as subatomic particles. (L.C)
J.J Thomson
What contribution did Newlands make to the systematic arrangement of the elements known to him? (L.C)
- Identified periodicity of properties
- Arranged in increasing relative atomic mass
Explain how Rutherford interpreted the results of his experiment to conclude that the atom has a nucleus. (L.C)
- Mass concentrated
- atom is mostly empty space
Describe an experiment carried out by Rutherford and his co-workers that led to the discovery of the nucleus. (L.C)
- He bombarded gold foil with alpha particles
- used zinc sulfide detector
- Most passed straight through
- Some deflected at large angles
- Some reflected
What is an isotope?
Atoms with the same atomic number (Z) but different mass numbers (A)
Complete and balance the following reaction:
HCl + Ca →
x
Complete and balance the following reaction:
Sulfuric acid + potassium oxide →
x
Complete and balance the following reaction:
Nitric acid + Lithium carbonate →
xx
What is a ‘salt’?
x
How many (i) electrons and (ii) neutrons in 35S2-?
x
What are metals?
x
What does every element in a group have in common?
x
Write a balanced equation between an alkaline metal and oxygen.
x
Are mass numbers always whole numbers? Explain your answer.
x
