Atomic Structure and the Periodic table
- Created by: Jmsmcn
- Created on: 18-09-17 16:50
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- Atomic Structure and the Periodic Table
- Atoms
- Atoms contain protons, neutrons and electrons
- The radius of an atom is about 0.1 nanometers
- The nucleus is in the middle
- It contains protons and neutrons
- It has a positive charge
- Almost all of the mass is here
- The elctrons move around the sphere in shells
- The volume of the shells determines the size of the atom
- Protons have 1 relative mass and +1 charge, netruons have 1 relative mass and no chrage, electrons have no mass and -1 charge
- The humber of electrons equalls the number of protons so atoms have no charge
- Ions have charge as protons to do not equal electrons
- Atomic number = number of electrons
- Atomic mass = number of protons + number of electrons
- Atoms contain protons, neutrons and electrons
- Elements
- Elements consist of atoms with the same number of protons
- Atoms can be represented by one or two letter symbols
- Isotopes are the same but they have different numbers of neutrons
- Carbon-12 has 6 netrons but carbon-13 has 7 neutrons
- Because elements can be different isotopes the relative atomic mass on the periodic table is an average which takes into account the different masses and their abundance
- Compounds
- Atoms join together to make compounds
- Compounds formed of two or more elements held together by chemical bonds
- Making bonds involves giving, taking, or sharing electrons
- The reactions are difficult to undo
- Metals and non-metals form ions and because they become oppositely charged they are strongly attracted to each other
- Compounds formed from nonmetals consist of molecules, they share electrons
- The properties of compounds are different from the individual atoms
- A formula shows what atoms are in a compound
- The letters represent the elements
- The numbers represent the number of those elements
- Atoms join together to make compounds
- Chemical Equations
- Chemical changes are shown using chemical (word) equations
- Left hand side shows rectanats
- Right hand side shows products
- Symbol equations show the reaction using the element symbols
- Symbol equations need to be balanced
- There mest be the same number of atoms on both sides
- You balance equations by putting numbers before elements/ compounds
- You CANNOT change the small numbers only add big numbers until the atoms are equal on both sides
- Chemical changes are shown using chemical (word) equations
- Mixtures and Chromato-graphy
- there are no bonds in mixtures so they are easily separated
- Parts of a mixture can be elements or compounds
- The chemical properties of a compound are not affected by being in a mixture
- Air is a mixture of gases
- Chromato-graphy is a way is separating substances in a mixture
- Put the mixture on a piece of filter paper
- Put it in water (but not the mixture)
- the water will seep up the paper pulling the micture
- You end up with a series of spots called a chromato-gram
- More Separation Techniques
- Filtration separates insoluble solids from liquids
- It can also be used for purification
- To separate soluble solids from a liquid:
- Evaporation: heat the liquid until all you have left is dry crystals
- Crystallization put the liquid in a dish and gently heat.
- Then when cyrtsalls start to form remove the dish from the heat
- The crystals should start to form in the cold highly concentrated liquid
- Fiklter the crysals out and leave to dry
- The crystals should start to form in the cold highly concentrated liquid
- Then when cyrtsalls start to form remove the dish from the heat
- Filtration and crystallization can be used to seperate a soluble and insoluble solid
- Filter to remove the insoluble solid
- Crystallize to remove the soluble solid
- Filtration separates insoluble solids from liquids
- Distillation
- Simple distillation is used to separate a liquid from a solution
- The solution is heated and the substance with the lowest boiling point becomes a vapor
- It is the condensed and collected
- It can only be used for things that have very different boiling points
- The solution is heated and the substance with the lowest boiling point becomes a vapor
- Fraction distillation is used to separate a mixture of liquids.
- Hot crude oil is pumed into the column
- Most things evaporate and move to the colder top
- Fractions that have a low boiling point move very far up before they condense - when they condense they are extracted down a pipe
- Fractions that have a high boiling pint condense quicker, and bitumen does not boil at all but it goes down a pipe at the bottom
- LPG does not condense and goes out as a gas at the top of the tower
- Fractions that have a low boiling point move very far up before they condense - when they condense they are extracted down a pipe
- Most things evaporate and move to the colder top
- Hot crude oil is pumed into the column
- Simple distillation is used to separate a liquid from a solution
- History of the Atom
- J J Thomson can up with the plum pudding model - there is a ball of positive charge and electrons stuck in it
- Rutherford did an experiment - he shot alpha particles through a thin sheet of gold
- He expected them to pass through because the positive charge was very spread out
- But some where deflected back
- He concluded that there was a tiny positive mass with electrons floating around it
- He expected them to pass through because the positive charge was very spread out
- Scientists realized that a cloud of electrons would be attracted to the nucleus and it would collapse
- Bohr presented the idea of shells so electrons have fixed orbits. The theory was supported by experiments and observations
- Experiments showed that proton and neutrons existed separately
- Bohr presented the idea of shells so electrons have fixed orbits. The theory was supported by experiments and observations
- Electronic Structure
- Electrons occupy shells (sometimes called energy levels)
- The lowest energy levels are filled first - these are closet to the nucleus
- Only a certain number of electrons are allowed in each shell
- 1st shell = 2
- 2nd shells = 8
- 3rd shell = 8
- Atoms want a full outer shell - like the noble gases in group 0
- They react to do this
- Electronic Structure
- Electrons occupy shells (sometimes called energy levels)
- The lowest energy levels are filled first - these are closet to the nucleus
- Only a certain number of electrons are allowed in each shell
- 1st shell = 2
- 2nd shells = 8
- 3rd shell = 8
- Atoms want a full outer shell - like the noble gases in group 0
- They react to do this
- They react to do this
- Electronic Structure
- They react to do this
- Development of the Periodic Table
- In the early 1800s elements were placed in order of relative atomic mass as scientists did not know about protons
- However they were not complete and therefore some elements were placed into the wrong group
- Mendeleev put elements mainly in order of relative atomic mass but also the properties
- For example Te and I were swapped because they had similar properties to the groups they were switched to
- Gaps were left so elements had similar patterns to their groups
- When the missing elements were found to fit the pattern it helped prove his theory
- Because of the existence of isotopes Mendeleev was right not to put them in order of relative atomic mass only
- In the early 1800s elements were placed in order of relative atomic mass as scientists did not know about protons
- Modern Periodic Table
- The peridoic table shows all of the elements listed in order of proton number
- Because they are orderd like this there are repating patterns
- Metals are to the left and non-metals are to the right
- Elements with similar properties form columns these are called groups
- The group number is the number of electrons in the outer shell
- But in group 8/0 helium only has two in its outer shell
- This is useful as the way atoms react depends on the number of electrons in the outer shell so groups have the dame properties
- In group one as you go down reactivity increases
- In group 7 reactivity goes down as you go down the group
- Each period represents a new full shell of electrons
- The peridoic table shows all of the elements listed in order of proton number
- Group 1 Elements
- The alkali metals are reactive and soft
- They each have one electron in their outer shells which makes them reactive and similar.
- As you go down they get more reactive as the electron is further from the nucleus (less attraction)
- As you do down the group the soling points and melting points lower
- They form ionic compounds
- They don't need much energy to form an 1+ ion
- They genarlly form white solids that dissolve in water to form a colourless liquid
- When put in water the produce hydrogen gas and metal hydroxides (a base)
- The further you go down the more energy given out (potassium gives out enough energy to ignite hydrogen)
- When heated in chlorine gas it forms metal chloride salts
- Different types of oxide will form depending on the element
- Lithium forms lithium oxide
- Sodium forms sodium oxide, and sodium peroxide
- Potassium form potassium peroxide and potassium superoxide
- Group 1 metals have different properties to transition metals
- They are more reactive than transition metals
- They are less dense, strong, and hard than transition metals
- They have lower boiling points than transition metals
- The alkali metals are reactive and soft
- Group 7 Elements
- They are non-metals with coloured vapors
- Fluorine is a very reactive, poisonous yellow gas
- Chlorine is a fairly reactive, poisonous, green gas
- Bromine is a dense poisonous, red/brown, volatile liquid
- Iodine is dark grey crystals, or a purple vapour
- As you go down it: becomes less reactive (harder to gain and electron, less attraction), has higher melting and boiling points
- From -1 ions called halides to bond with metals
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- They are non-metals with coloured vapors
- Group 0 Elements
- They are all colourless intert gases
- They have a full outer shell so they are stable and therefore they do not need to react (inert)
- As they are inert they do not burn
- They are monatomic gases (they are not bonded)
- The boiling points increase as you move down
- This is because there are more electrons so there is a greater inter-molecular force
- They are all colourless intert gases
- Metals and Non-Metals
- Most element are metals - they are towards the left and bottom of the periodic table. They are elements that form positive ions when they react
- Non-metals are at the far tight and top of the periodic table and generally form negative ions
- Metals only have a few electrons on the outer shell so it is easy and does not require much energy to lose them and from a positive ion
- Non-metals have lots of electrons on the outer shell so they cannot lose them. This means they gain or share electrons to form a full outer shell - this causes negative ions
- Metals have metallic bonding which means they are strong, can conduct heat and electricity, malleable, and they have high melting and boiling point
- Non-metals are dull, brittle, and generally do not conduct heat and electricity
- Transition meatls are in the middle section and they can form more than one ion, are coloured, they make good catalysts
- Atoms
- Chlorine is a fairly reactive, poisonous, green gas
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