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67 Cards in this Set
- Front
- Back
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Greek philosophers atomic model |
Matter was made up of a single continuous substance that produced the 4 elements -earth,fire,water and air. |
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Robert Boyle atomic theory |
Proposed that there were some some substances that could not be made simpler.these were the chemical elements as we now know them. |
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John Dalton atomic idea |
Suggested that the elements were composed of indivisible atoms.all the atoms of a particular elements had the same mass and atoms of different elements had different masses. Atoms could not be broken down. |
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Waht did Henri becquerel do? |
He discovered radioactivity. |
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What did radioactivity show? |
Showed that particles could come from inside the atoms . |
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The result of radioactivity? |
Therfore the atom was not indivisible. |
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Who discovered electron? |
J J Thomson |
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......... was the first subatomic particle to be discovered |
Electron |
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What did Thomson show? |
That electrons were negativley charged and the electrons from all elements were the same |
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As electrons were negativley charged there had to be .... |
Some source of positive charge inside the atoms |
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As electrons were much lighter than than whole atom , there had to be.... |
Sth to account for the rest of the mass of the atom |
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What did Thomson suggest? |
Electrons were located within the atom in circular arrays , like plums in a pudding of positive charge |
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What did Ernest Rutherford and his team find? |
That most of the mass and all positive charge of the atom was in a tiny central nucleus |
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For many years it has been known that atoms are made up of particles called.....1..... and the complete picture is still being built up in ..2....such as the one in CERN , near Geneva |
1. subatomic particles 2. Atom smashers |
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Smasher |
در هم شکننده خرد کننده |
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...... is the instrument used to take photos of xenon atoms |
Scanning tunnelling electron microscope |
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Mass of proton/kg |
1.673×10 -27 |
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Mass of electron/kg |
0.911×10 -31 ( very nearly 0) |
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Mass of neutron/kg |
1.675×10 -27 |
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Relative mass of p , n , and e |
P = 1 n=1 e=1÷1840 |
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Charge / C for p n e |
P= + 1.602×10 -19 e= - 1.602×10 -19 n=0 |
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What is strong nuclear force? |
the force that holds protons and neutrons together whitin the nucleus of the atom and is much stronger than electrostatic forces and it overcomes the repulsion between protons in the nucleus and it acts only over very short distances that is within the nucleus. |
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What is electrostatic forces? |
The forces of attraction and repulsion between electrically charged particles |
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Electron are found in the series of levels , sometimes referred to as ? |
Orbits or shells which get further and further away from the nucleus |
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*Why we assume that there are the same number of protons and electrons in an atom? |
In a neutral atom it must be same because their charge is equal in size and opposite in sign |
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The diameter of the nucleus of a hydrogen atom is..1..... while the diameter of the atom itself is....2... which is about 50000 time larger |
1. 2×10 -15 2. 1× 10 -10 If the nucleus were the size of a fly , the whole atom would be roughly a size of a cathedral |
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The number of protons in the nucleus is called ........ or ...... |
Atomic number or proton number Z |
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The numbers of electrons in the outer sell of an atom determines the ........ |
Chemical properties of an element ( how it reacts ) and what sort of elements it is |
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The ........ number defines the chemical identity of an element |
Atomic number |
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All atoms of the same element have the same ..... number |
Atomic |
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Mass number? |
The total number of protons plus neutrons in the nucleus or the total number of nucleons is A |
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What 's isotope? |
Atoms with the same number of protons and different numbers of neutrons are called isotopes |
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Different isotopes of the same element react chemically in exactly the same way as they have the same...... |
Electron configuration |
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The superscript represents .1.... number and subscript represents ..2.. number |
1 mass number 2 atomic number |
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The mass number of an isotope must always be ..... than the atomic number |
Bigger except H or hydrogen Typically it is around twice as big |
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Carbon-14 abundance is |
Trace مقدار کم ناچیز رد پا اثر گذاشتن |
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Carbon -12 has the .... abundance |
The most abundance 98.89% And carbon-13 is 1.11% |
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What's the cause of radioactivity? |
Sometimes isotopes are unstable and the nucleus of the atom itself breaks down giving off bits of the nucleus or energetic rays. |
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What is a half- life ? |
Each radioactive isotope decays at a rate measured by its half life , this is the time taken for half of its reactivity to decay. |
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Carbon-14 is a well known radioactive isotope which has a half life of..1.. and is produced by .....2.. in the atmosphere |
5730 years Cosmic ray activities |
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Explain carbon dating? |
There is always a tiny fixed proportion of C-14 in all living matter . All living matter takes.in and gives out C in the form of food and co2 respectively. As a result the level of C-14 stays the same .once the living material dies this stops happening and the radioactive c breaks down and the level of radioactivity slowly falls, knowing the half life of c14 scientists work backwards. How long it has taken for a level of radioactivity to fall from what it is in a living organism to what it is in the sample.so a sample with a half level of radioactivity expected in a living organism would have been dead for 5730 years. |
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Radiocarbon dating was introduced in 1949 by |
The American Willard Libby |
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How does carbon 14 producem |
Is produced in the atmosphere a nuclear reaction in which a neutron (from cosmic ray)hits a nitrogen atom and ejects a proton |
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Beta decay |
A neutron turns in to a proton + beta particle ( a superfast electron) so the number of neutron decreases and the number of protons increases and the atomic mass number won't change |
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Alfa decay |
The number of protons decrease by 2 and number of neutrons by 2 and atomic mass number by 4 |
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What happens if an element gains beta particle |
Beta means n-p so it gains a neutron therfore the number of neutron increases by 1 but simultaneously looses 1 proton and the atomic mass number won't change at all |
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Niels Bohr put forward the idea that...... |
The atom consisted of a tiny positive nucleus orbited by negativley charged electrons to form an atom like a tiny solar system. The electrons orbited in sells of fixed size and the movement of e from one shell to the next explained how atoms absorbed and gave out light this was the the beginning of waht is called quantum theory |
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Erwin schrodinger a mathematical physicist worked out .... |
An equation that used the idea that electrons had some of the properties of waves as well as of those of particles.this led to a theory called quantum mechanics which can be used to predict the behaviour of subatomic particles. |
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James chadwick discovered..... |
Neutron |
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Gilbert Lewis Put forward the ideas that: |
1. The inertness of the noble gases was related to their having full outer shells of electrons 2.ions were formed by atoms losing or gaining electrons to attain their full outer shells 3.atoms could also bond by sharing electron to form full outer shells |
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.......... theories are the base of modern ideas of chemical bonding and explains the formulae of many simple compounds using the idea that atoms tend to gain the stable electronic structure of the nearest Nobel gas |
Lewis 's |
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Early theories model the electrons as a .......... |
Minute solid particle |
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Later theories suggest you can think of electrons as |
Smeared out clouds of charge so you can never say exactly where an e is at any moment. You can merely state the probability that it can be found in a particular volume of space that has a particular shape |
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Dalton's model can still be used to explain the .... |
Geometries of crystals |
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Bohr's model can be used for a simple model of ..... |
Ionic and covalent bonding |
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The charge cloud idea is used for ... |
More sophisticated explanation of bonding and the shape of molecules |
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The simple model of electrons orbiting in shells is useful for many purposes , particularly for .... |
Working out bonding between atoms |
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Electron diagrams can still be useful in .... |
Predicting and explaining the formulae of simple compounds and the shapes of molecules |
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The number of electrons in each shell is |
2n squar |
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Electron diagrams in shorthand? |
Write the number of electrons in each shell , starting with inner shell and working outwards Seperate each number by comma |
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Empirical formula |
That represents the simplest whole number ratio of atoms of each element that present in a compound |
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How to find empirical formula |
1.find the mass of each element present in the compound 2.find the number of moles of atoms of each element 3.convert the number of moles into a whole number ratio |
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Molecular formula |
Gives us the actual number of atoms of each element in one molecule of the compound.(it applies only to substances that exists as molecules) |
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Empirical formula is not always the same as molecular formula why? |
Because there may be several units of empirical formula in the molecular formula |
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How to find the number of units of the empirical formula in the molecular formula? |
Divide the relative molecular mass over relative mass of empirical formula |
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What is the Stoichiometriy of the reaction ? |
The ratio in which reactants react and products are produced in simple whole numbers is called the Stoichiometriy of the reaction |
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Some ions do not really take part in the reaction so we call them..... |
Spectator ions |
