Atomic Structure And The Periodic Table (C1) Flashcards
What is the radius of an atom?
0.1nm
1X10^-10m
What is the Nucleus?
The Nucleus is the centre of an atom. The Nucleus... - has protons - has neutrons - has an overall positive charge - contains (most) of an atom's mass - has a radius of 1X10^-14m (1/10,000th of an atom) (See Figure 1, Page 1)
What are Electrons?
Electrons are negatively charged sub atomic particles.
Electrons…
- move around the nucleus in orbiting electron shells
- are negatively charged
- are extremely small but cover a lot of space
- volume of their orbits are defined by the size of the atom
- have virtually no mass
What are the 3 subatomic particles and their relative charges and mass.
Particle - Relative Mass - Relative Charge
Proton = 1 = +1
Neutron = 1 = 0
Electron = (>0) = -1
What is the charge of an atom?
Neutral as they have equal protons (+1) as electrons (-1)
What is an ion?
An atom which has gained or lost electrons (often to obtain a full outer shell)
What is the charge of an ion?
It is the amount of protons - the amount if electrons on the ion.
If it has 2 more electrons than the original atom, it has a charge of 2-
If it has 3 less electrons than the original atom, it has a charge of 3+
What is the Mass Number?
Mass of the atom - protons + neutrons
See Figure 2, Page 1
What is the Atomic Number?
Number of protons in an atom
See Figure 2, Page 1
What defines what element an atom is?
Atomic Number defines the element of an atom. This never changes.
What is an element symbol and what is it good for?
Every element has their own unique symbol. This consists of 1 or 2 letters usually derived from Latin.
The first letter is always capital (and if there is a second it is always lower case)
These symbols are shorthand and universal.
(See Figure 2, Page 1)
Roughly how many different elements exist?
Around 100
What is an isotope?
An isotope is an atom of a specific element that has the ‘wrong’ number of neutrons.
(For example if a carbon atom (that typically has 6 protons, 6 neutrons and 6 electron) has instead 6 protons 7 neutrons and 6 electrons. It is still the same element as the number of protons hasn’t changed and it is still a neutral atom as there are still equal protons and electrons.)
Why do some periodic tables have mass numbers with decimal places?
Isotopes occur naturally and we can calculate their abundance. This is why on more specific periodic tables may have decimal places on their mass numbers.
How do you calculate the relative atomic mass of an isotope?
Relative Atomic Mass (Ar) = sum of (isotope abundance X isotope mass number / sum of abundances of all the isotopes
What is a Compound?
When two or more particles react and chemically join together, they form compounds. They are usually difficult to separate.
What do we call the bond made by a metal and non-metal?
This is called an ionic bonding.
The metal loses electrons to form a positive ion and the non-metal gains some electrons. The opposite forces attract.
What do we call the bond made by a metal and metal?
This is called metallic bonding. The metals form positive ions by loosing electrons. These electrons form a sea of delocalised electrons around the ions, holding the metals together.
What do we call the bond made by a non-metal and non-metal?
This is called covalent bonding. Each atom shares an electron with another as both nuclei are pulling the electron.
What is a Chemical Formula?
Th Chemical Formula is the letters used to symbolise a compound. For example 1 Sodium Atom (Na) plus 1 Chlorine Atoms (Cl) creates Sodium Chloride. The formula for this is NaCl. If there is more than one of either atom, there will be a small number symbolising it to the left corner of the symbol. If there is more than one molecule, there will be a large number in front of the formula.
What are the two types of ways of showing Chemical Equations?
Word Equations
Symbol Equations
What is a Word Equation?
This is when you write the name of the elements reacting (on the left), then an arrow (showing the reaction) and finally the written name of the product(s).
What is a Symbol Equation?
This is when you write the symbols of the elements reacting (on the left), then an arrow (showing the reaction) and finally the symbols of the product(s). These must be balanced.
What does it mean if a Symbol Equation is balanced?
Balancing is important for all symbol equations, this is due to the law of conservation of mass. If an equation is balanced it means there is an equal amount of each element on either side of the equation. For example if there is 1 carbon atom reacting to make 1 carbon dioxide molecule, there must also be 2 oxygen molecules reacting.
What is the Law of Conservation of Mass?
Conservation of mass states that mass can neither be created nor destroyed.
What is Chromatography used to separate?
Dyes in an ink
Describe the process of Chromatography.
1) Draw a pencil line near the bottom of filter paper
2) Add a spot of ink along the line and place the sheet in a solvent (e.g water) without the ink entering the liquid
3) Place a lid on the top to prevent evaporation
4) Any insoluble dyes will stay at the line and the colours will separate up the paper depending on how soluble that are.
5) The end result is called a chromatogram
(See Figure 4)
What is Filtration used to separate?
Separate an insoluble solid from a liquid.
Describe the process of Filtration.
1) Fold paper into a triangle and place it in a funnel
2) Place the funnel in a beaker
3) Pour in your solution
4) The insoluble solid will be left in the filter paper and the liquid in the beaker
(See Figure 5)
What is Evaporation used to separate?
To separate a soluble solid from a set solution.
Describe the process of Evaporation.
1) Pour the solution into an evaporating dish
2) Slowly heat the solution, the solvent will evaporate and become more concentrated
3) Crystals will begin to form
4) Keep evaporating until dry crystals are left
(See Figure 6)
What is Crystallisation used to separate?
To separate a soluble solid from a set solution.
Describe the process of Crystallisation.
1) Pour the solution into an evaporating dish and heat gently
2) When crystals start form, remove and allow to cool
3) Filter the crystals out of the solution and leave in a warm place to dry. You could also use a drying oven or a desiccator
(See Figure 7)
What is Simple Distillation used to separate?
Separate a mixture of two (+) liquids with different boiling points.
Describe the process of Simple Distillation.
1) Heat the solution, the liquid with the lower boiling point will thus evaporate
2) The evaporated liquid will enter a condenser with cold water and condense
3) When the thermometer shows you have reached a high enough temperature for the first to have fully evaporated, switch of the heat and allow to cool.
4) The liquid with a higher boiling point will be left in the flask with the other in a beaker at the end of the condenser.
(See Figure 8)
What is Fractional Distillation used to separate?
Separate a mixture of two (+) liquids with more similar boiling points. (too close for simple distillation)
Describe the process of Fractional Distillation.
1) Heat the solution, the liquid(s) with the lowest boiling point will evaporate up through the fractional column
2) This column gets colder the higher up it is and thus if a liquid with a slightly higher melting point has evaporated it will condense here
3) The liquid with the lowest melting point will condense in the condenser and fat into a beaker/ test tube below
4) When the thermometer indicates that the liquid with the lowest melting point should have fully evaporated, put a different test tube under the condenser and increase the heat.
(See Figure 9)
What did John Dalton believe was the structure of an atom?
Start of the 19th Century?
Solid spheres.
Different spheres made up different elements.
What did JJ Thomson believe was the structure of an atom?
1897
Plum pudding model -
a ball of positive charge with negative electrons stuck in it
(pudding with plums studded in it)
What did Ernest Rutherford believe was the structure of an atom?
1909
Mostly empty space with a dense positive nucleus, with a cloud of negative electrons surrounding it
What did Niels Bohr believe was the structure of an atom?
1913
Electrons orbit the nucleus at specific energy levels (shells)
What did James Chadwick believe was the structure of an atom?
1932
Discovered evidence of a neutral sub atomic particle which provides mass
How did Rutherford prove his theory?
Alpha Particle Scattering Experiment
Describe what occurred during the Alpha Scattering Experiment and what happened
Alpha particles were shot at gold foil which was only (theoretically) 1 atom thick
Most particles went right through
Some particles deflected of at angles
A few particles were shot straight back
What did the Alpha Particle Scattering Experiment prove?
- Atoms are mostly space
(most particles went right through the foil) - Atoms have a very dense nucleus
(some particles were deflected off at angles - this was like shooting a bullet at paper and it bouncing off) - Atoms have a positive nucleus
(alpha particles are positively charged and thus would have been attracted to negative sub atomic particles but reflected off of positive ones)
How many electrons fit in each shell?
Shell 1 - 2 Shell 2 - 8 Shell 3 - 8 Shell 4 - 8 etc...
In which order are shells filled?
From nearest to furthest from the nucleus
What is a shell?
An energy level around an atom
What happens when the outer shell is not full?
The atom is more reactive because it does not have the stable ‘noble gas structure’
What were elements in the early periodic table arranged by?
Physical and Chemical properties
Relative comic mass
Why did Dimitri Mendeleev leave gaps on his periodic table?
For undiscovered elements he predicted exist
By what did Mendeleev organise his periodic table?
Atomic mass but with some elements slightly switched depending on their properties
What confirmed that elements do not need to be in strict order of atomic mass on the periodic table?
The discovery of isotopes in the early 20th centruary
When did Dimitri Mendeleev exist?
Early 1800s
What is the modern periodic table arranged in?
Increasing proton number
What is similar in each group
Properties
number of electrons in the outer shell
Where are the noble gasses?
Group 0/8
Where are halogens?
Group 7
Where are alkali metals?
Group 1
Where are earth metals?
Group 2
Most elements are…?
Metals
What type of ions do metals form?
Positive Cations
Where are metals on the periodic table
All elements in Groups 1 and 2 as well as the transitional metals are metals There are also: 4 metals at the bottom of group 3 3 metals at the bottom of group 4 2 metals at the bottom of group 5 1 metal at the bottom of group 6
What type of ions do non-metals form?
Negative Anions
Are elements in groups that form cations more or less reactive going down the group?
More reactive as they are trying to lose an electron
This is easier if they are further from the positive nucleus
Are elements in groups that form anions more or less reactive going down the group?
Less reactive as they are trying to gain an electron
This is easier if they are near the positive nucleus
Describe 5 general properties of metals
Strong Malleable Conduct heat Conduct Electricity Have high melting/ boiling points
Describe 5 general properties of non-metals
Brittle Dull looking Lower Density Do not conduct electricity Not always solid at RTM (room temperature)
Where can transitional metals be found?
Between Group 2 and 3
Describe some ‘special’ properties of transition metals
Colourful
Good Catalysts
Can form multiple ions
Which are the generally most reactive metals?
Group 1
Alkali Metals
How many electrons do alkali metals have in their outer shell?
1
Describe the properties of alkali metals
Soft
Low Density
What is the trend of reactivity of alkali metals?
Alkali Metals (Grp 1) Increase in reactivity down the group
Why do alkali metals increase in reactivity down the group?
As the electron that they want to loose is further from the nucleus, the strength of attraction is lesser and thus less energy is needed to break the bond
What decreases down the group of alkali metals?
Melting and boiling point
How do Group 1 metals react in water and what do they produce?
Vigorously
Produce hydrogen gas and metal hydroxides (salts which dissolve in water to produce an alkaline solution)
(2Na+2H2O -> 2NaOH+H2)
How do Group 1 metals react with chlorine and what do they produce?
Vigorously when heated with chlorine gas
Form white metal chloride salts
(2Na+Cl2 -> 2NaCl)
How do Group 1 metals react with oxygen and what do they produce?
Not a vigorous reaction
Form Metal Oxides
(can form oxides, peroxides and superoxides)
What are Halogens
Group 7 Non-Metals
At RTM, most halogens are…?
Gas or Liquids
What is the trend of reactivity of halogens?
Decrease down the group
What decreases down the group of halogens?
Melting and boiling point
Why do alkali metals increase in reactivity down the group?
As they only want to gain one electron into their outer shell, this is easiest when the positive nucleus is newest the outer shell as the force of attraction is strongest. As the outer shell becomes further away, more energy is needed to attract the electron.
What is a displacement reaction?
When a more reactive element takes the place of a less reactive one in a compound
Halogens often do this
(Cl2+2KI -> I2+2KCl)
What are Noble Gasses?
Group 0/8 Non-Metals
Describe the trend in reactivity of Noble Gasses
None
They have full outer shells and thus do not react
How do Noble Gasses exist at RTM?
Monatomic, colourless gasses
How flammable are Noble Gasses?
Not
What increases down Group 0
Boiling point
