Atomic Structure & Periodic Table Flashcards
What was John Dalton’s theory about the development of the atom? (4 marks)
Matter is made of atoms which are tiny particles that cannot be created, destroyed, or divided
Atoms of the same element are identical, and atoms of different elements are different
Different atoms combine together to form new substances
What did J.J Thompson’s plum pudding model suggest about the atom?
Atoms have no overall charge. There must be a positive charge to balance out the negative charge.
The plum pudding model contains electrons within a positively charged ball. The electrons are arranged randomly within a positive charge and the mass is spread evenly throughout the atom.
How did Rutherford explain the scattering of alpha particles by gold atoms?
A positive charge is concentrated in the centre of the atom, so like charges will repel.
What does Rutherford’s nuclear model suggest?
Most of the atom’s mass is concentrated in the nucleus, which contains positively charged particles. The atom consists mainly of empty space and the electrons orbit around the nucleus (cloud).
What was Rutherford’s experiment?
Rutherford shot a beam of positively charged particles (alpha particles) at a thin sheet of gold foil
What were the expected results in Rutherford’s experiment?
He expected the particles to pass through the foil because the positive charge of the nucleus was thought to be evenly spread out.
What were the actual results of Rutherford’s experiment
Some particles were scattered, however, a few were deflected directly back.
What was John Dalton’s suggestion for the periodic table?
He arranged the elements in order of their atomic weights.
How did John Newland build on John Dalton’s ideas?
He arranged the known elements in order of mass but noticed that the properties of every eighth element seemed similar. Hence he produced a table showing the ‘Law of Octaves’.
What was the problem with John Newland’s ‘Law of Octaves?’
He assumed all the elements have been found, even though chemists were still discovering new ones.
He filled in his octaves even if the elements weren’t similar.
The table only worked for known elements up to calcium (16) before the pattern broke down.
How did Mendeleev set up the modern periodic table?
He placed the elements in the order of their atomic weights.
He then arranged the elements so that a periodic (regularly occurring)
pattern in their properties could be seen.
How is the periodic table based on atomic structure?
The atomic number gives the number of electrons
The elements are ordered by the number of protons they have
The elements are put in groups where the number of shells increases as you go down the group.
Why were some elements not placed in the order of increasing atomic weight in Mendeleev’s periodic table?
So that the elements could fit into the proper groups (similar elements have similar chemical properties)
What did the Bohr Model suggest about electrons? (4 marks)
That electrons orbit the nucleus in fixed shells located at set distances from the nucleus. Each shell has a different energy associated with it, with the higher energy shells being located further away from the nucleus.
How did the Bohr Model prevent the atom from collapsing and why?
The orbiting of the electrons prevents the atom from collapsing inwards due to the attraction between the positive nucleus and negative electrons circling the nucleus.
What did James Chadwick’s experiment provide evidence for?
The neutron, which must have no charge and the same mass as a proton
Why is the ending of -ide used in ionic compounds?
-ide is used if the compound contains just two elements
Why is the ending of -ate used for ionic compounds?
-ate is used if the compound contains three or more elements, one of which is oxygen
Why are group 1 metals known as alkali metals?
They form alkaline solutions when they react with water. An alkaline solution is formed when a base solid dissolves in water.
What are the properties of group 1 metals? (3 marks)
They are all soft metals that can be easily cut with a knife.
They are very reactive (as they only need to lose one electron in order to become stable)
They have relatively low densities and low melting points.
Why do alkali metals have similar chemical properties?
They have 1 electron in their outer shell which determines their reactivity.
Why do the melting points of the alkali metals decrease as you go down the group?
The increase of shells decreases the attractive forces between outer electrons and positive ions
What compunds are formed when a group 1 metal reacts with a non-metal?
When a group 1 element reacts its atoms only need to lose one electron, as there is only 1 electron in the outer shell. Hence they form ionic compounds with 1+ ions.
Why do alkali metals get more reactive as you go down the group? (6 marks)
The atoms of each element get larger
going down the group, this causes an increase of shells.
This means that the outermost electron gets further away from the nucleus, so there are weaker forces of attraction between the outermost electron and the nucleus.
Therefore, less energy is required to overcome the force of attraction so the outer electron is lost more easily in reactions.
Group 1 metal reaction with water
lithium + water —> ………. + ……….
lithium + water —> lithium hydroxide + hydrogen
Group 1 metal reaction with water
Li + H₂O —> …. + …..
Li + 2H₂O —> 2LiOH + H₂
How does lithium react when placed in water?
It’s a relatively low reaction. There is some fizzing.
How does sodium react when place in water?
A large amount of heat is released which causes the sodium to melt and form a ball.
Hydrogen released catches fire and causes the ball of sodium to dash across the surface.
How does potassium react when placed in water?
There is enough heat released so the hydrogen burns with a lilac flame
The potassium melts into a shiny ball that dashes across the surface.
Group 1 metal reaction with oxygen
Sodium + Oxygen —> ………
Sodium + Oxygen —> Sodium Oxide
Group 1 metal reaction with oxygen
Na + O₂ —> ……
4Na + O₂ —> 2Na₂O
Why do alkali metals tarnish when exposed to air?
Because they form thin layer of oxide on their surface, which in turn react with moisture to form hydroxides.
Group 1 metals with chlorine
Potassium + chlorine —> …..
Potassium + chlorine —> Potassium Chloride
Group 1 metals with chlorine
2K + Cl₂ —> ….
2K + Cl₂ —> 2KCl
What do group 1 metals react with chlorine to form?
the same for iodine, bromine, fluorine
They produce metal chlorides.
What are the physical properties of the transition metals?
They are very lustrous (shiny), they are hard and strong, and they are good conductors of both heat and electricity.
Transition metals have a high density and high melting points.
What are ions?
They are charged particles.
