Flashcards
Atomic Structure and the Periodic Table
Cards in this deck (75)
- 1Atoms contain protons, neutrons and electrons.
- 2The nucleus- In the middle of the atom
- Has a positive charge because of the protons
- Almost the whole mass of the atom is concentrated in the nucleus. - 3The electrons- Move around the nucleus in electron shells
- They're negatively charged and tiny, but they cover a lot of space
- Virtually no mass - 4Number of protons =Number of electrons
- 5Atoms are neutral, they have no charge overall.This is because they have the same number of protons as electrons
- 6The charge on the electrons is the same size as the charge on the protons.Only opposite - so they cancel each other out (neutral)
- 7In an Ion the number of protons DOESN'T equal the number of electrons.This means that it has an overall charge
An ion with a 2- charge has two more electrons than protons. - 8The atomic number tells you how many PROTONS there areThe mass number tells you the total number of protons and neutrons in the atom.
- 9To get the number of electronsJust subtract the atomic number from the mass number
- 10Mass number is on the Atomic number is on theMass = top
Atomic = bottom
- 11Elements consist of atoms with the SAME atomic number.Atoms can have different numbers of protons, neutrons and electrons. It's the number of protons in the nucleus that decides what type of atom it is.
- 12All the atoms of a particular element havethe SAME NUMBER OF PROTONS.
- 13Isotopes areThe same element except for extra NEUTRONS
- 14They still have the same number or protons, just different number of neutrons.Isotopes have the same ATOMIC NUMBER but different MASS NUMBERS
- 15—
- 16Because many elements can exist as a number of different isotopes, relative atomic mass (Ar) is used instead of a mass # when referring to the element as a whole.This is an AVERAGE mass taking into account the different masses and abundances (amounts) of all the isotopes that make up the element.
- 17You can use this formula to work out the Ar of an element
- 18Example:
- 19Atoms join together to makeCompounds
- 20All the elements in a compound are held together byChemical Bonds
- 21Making bonds involvesAtoms giving away, taking in or sharing electrons. ONLY the ELECTRONS are involved - the nuclei of the atoms aren't affected.
- 22Metal atoms _________ to form _________ ionsLose
Positive - 23Non-Metal atoms ________ to form _________ ionsGain
Negative - 24The opposite charges of the ions mean that they arestrongly attracted to each other.
- 25This is calledIonic Bonding
- 26A compound formed from non-metals consists ofmolecules.
- 27Each atom SHARES an electron with another atom - this is calledCOVALENT BONDING
- 28The properties of the compound are usually totally different from the properties of the original elements
- 29Just as elements can be represented by symbols, compounds can be represented by formulas.The formulas are made up of elemental symbols in the same proportions that the element can be found in the compound.
- 30e.g Carbon Dioxide is a compound formed from a chem reaction between carbon and oxygen. It contains 1 CARBON ATOM and 2 OXYGEN ATOMS
- 31There might be brackets in the formula. E.g calcium hydroxide is Ca(OH)2The little number outside the brackets applies to everything in the brackets.
So this is:
1 calcium, 2 oxygen and 2 hydrogen - 32Chemical changes are shown using chemical equations
- 33Symbol equations show the atoms on both sides.There is a '2' in front of the Mg and the MgO - this is explained next.
- 34Symbol equations may need to be balanced.Example:
- 35The formulas are correct, but some of the numbers of atoms don't match up on both sides.The only thing you can do is make it a 2H²O instead of H²O
- 36But now there are too many H ant O atoms on the R side.So to balance that you would put 2NaOH on the left.
- 37Mixtures are easily separated, unlike compounds.Unlike in a compound, there are no chemical bonds between the different parts of a mixture.
- 38The parts of the mixture can be either elements or compounds and they can be seperated out by physical methods such asfiltration, crystallisation, simple distillation, fractional distillation.
- 39The properties of a mixture are just a mixture ofthe properties of the separate part - the chemical properties of a substance aren't affected by it being part of a mixture.
- 40The theory of the atom structure has changed over time.The plum pudding model showed the atom as a ball of positive charge with electrons stuck in it.
- 41The model was tested by firing positively charged alpha particles at an extremely thin sheet of gold.From the model they were expecting the particles to pass straight through the gold or be slightly deflected at most. This was because the + charge of each atom was thought to be very spread out through the pudding.
- 42But whilst most of the atoms did go straight through the gold, some were deflected more than expected.This meant the model couldn't be right.
- 43They then came up with an idea to explain this new evidence - the nuclear model of the atom.In this, a tiny + charge nucleus at the centre where most of the mass is concentrated and a 'cloud' of - electrons surrounds this nucleus
- 44This meant most of the atom was empty space. When alpha particles are near the concentrated, + charge of the nucleus, they were deflected.If they were fired directly at the nucleus, they were deflected backwards. Otherwise they passed through the empty space.
- 45The nuclear model explains a lot. Scientists realised that the electrons in a 'cloud' around the nucleus would be attracted to the atom and cause it to collapse.The new nuclear model of the atom suggested that the electrons were contained in shells.
- 46Bohr (2nd version) proposed that the electrons orbit the nucleus in fixed shells and aren't anywhere in between.Each shell is a FIXED distance from the nucleus.
- 47Further experiments by Rutherford (1st version) and others showed that the nucleus can be divided into smaller particles, which each have the same charge as a hydrogen nucleus. These particles were namedProtons
- 48About 20 years after scientists had accepted that atoms have a nuclei, an experiment which provided evidence for neutral particles in the nucleus (neutrons) was conducted.The discovery of neutrons resulted in a model of the atom which is pretty close to the modern day accepted version.
- 49Electron shell rules:- Electrons always occupy shells
- The lowest energy levels (shells) are always filled first
- 1st=2 2nd=8 3rd=8
- Atoms are much happier when they have full electron shells - like the N/gases in G0 - 50In most atoms, the outer shells are not full, and this makes the atom want toreact to fill it
- 51Some examples of electronic structures
- 52In the early 1800s elements were arranged by atomic massAs a result of this, some elements were placed in the wrong group. This is because elements were placed in order or their Ar and did not take into account their properties.
- 53Dmitri Mendeleev left gaps and predicted new elements.He put the elements mainly in order of atomic mass, but did switch the order if the properties meant that it should be changed.
- 54Gaps were left in the table to make sure that elements with similar properties stayed in the same groups. Some of these gaps indicated the existence of undiscovered elements.This also allowed him to predict what their properties may be. When they were found, and they fitted the pattern, it helped confirm his ideas.
- 55—
- 56Modern periodic tableMetals are found to the left
Non metals to the right
- 57Elements with similar properties formColumns.
These vertical columns are called groups - 58The group number (1-7(-0)) tells you how many electrons there are in the outer shell.If you know the properties of one element, you can predict the properties of other elements in that group. For example, group 1 are all metals and all react in a similar way.
- 59You can also make predictions in trends in reactivity. As you go DOWN group 1, reactivity INCREASES. As you go DOWN group 7 the reactivity DECREASESThe rows are called periods.
- 60- Metals are elements which form ___ ions when they react - They're towards the bottom and left of the periodic table.A: Positive.
- Non-Metals are at the far right and top of the p/table
- Non-Metals don't generally form + ions when they react - 61Atoms generally react to form a full outer shell. They do this via losing, gaining or sharing electronsMetals to the left of the p/table don't have many electrons to remove and metals towards the bottom of the p/table have outer electrons which are a long way from the nucleus so feel a weaker attraction.
- 62Both these effects mean that not much energy is needed to remove the electrons so it's feasible for the elements to react to form + ions with a f/outer shell.For non-metals forming + ions is much more difficult. This is as they are either to the right of the p/table where they have lots of electrons to remove to get a full outer shell, or towards the top where the outer electrons are close to the nucleus and feel a stronger attraction.
- 63It's far more feasible for them to either ____ or ____ electrons to get a full outer shell.Share
Gain - 64All metals have metallic bonding which causes them to have similar basic physical properties.They're:
- Strong (hard to brake) but are malleable
- Great at conducting heat and electricity
- High boiling and melting points - 65As non-metals don't have metallic bonding they don't tend to exhibit the same properties as metals.They tend to be dull looking, more brittle, aren't always solid at room temp, generally don't conduct electricity and often have a lower density.
- 66Transition metals are found in the middle of the p/table. They are typical metals and have properties you would expect of a 'proper' metalDense
Strong
Shiny
Good conductors of heat and electricity - 67They also have some special properties- Can have more than 1 ion.
- Often coloured and so compounds containing them are colourful.
- Often make good catalysts. - 68Group 1 elements are reactive, soft elements.All have 1 electron in outer shell which makes them very reactive.
All soft and have a low density - 69As you go down group 1:- Increasing reactivity - the outer electron is more easily lost as it is further from nucleus
- Lower melting and boiling points
- Higher relative atomic mass. - 70G1 metals form ionic compounds with non-metals.When G1 metals are put in water they react vigorously to produce Hydrogen gas and metal hydroxides. The further down G1, the more violent the reaction. The amount of energy given out increases as you go down G1.
- 71G1 metals react vigorously when heated in chlorine gas to form white metal chloride salts.The further down G1, the more violent the reaction.
- 72G1 metals can react with oxygen to form metal oxide. Different types of oxide will form depending on the G1 metal:Lithium = Lithium oxide
Sodium = Sodium Oxide + Sodium Peroxide
Potassium = Potassium Peroxide + Potassium Superoxide - 73G1 metals have different properties to transition metals. G1 metals are much more reactive.They are also much less dense, strong and hard than the transition metals and have a much lower melting point (the exception is the transition metal mercury)
- 74G7 elements (Halogens) are all non-metals with coloured vapours
- 75As you go down G7- Less reactive (harder to gain an extra electron because further from the nucleus)
- Higher melting and boiling points
- Higher Ar
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- Year 10 Chemistry (1- Atomic Structure and the Periodic Table) Flashcards on Atomic Structure and the Periodic Table, created by Callum Corrigan on 16/06/2017.
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- Callum Corrigan
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