AS Level Chemistry
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AS Level Chemistry - Details
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| An atom contains dense (1) surrounded by shells of (2) | 1. Nucleus 2. Electrons |
| What two nucleons make up the nucleus? | Protons and Neutrons |
| Describe the charges and relative mass of each subatomic particle present | Electrons have a negative charge , and mass 1/1836 Protons have a positive charge, and mass 1 Neutrons are uncharged , and mass 1 |
| The atomic number can be known as this, and what is the atomic number | Atomic/ Proton number is the number of protons in the nucleus |
| What does every atom of the same element have in common? | Every atom of the same element has the same Atomic number |
| Mass number is also known as this, what is the mass number | Mass number ( nucleon number) is the number of protons plus the number of neutrons in the nucleus of an atom |
| What are isotopes? | Isotopes are atoms of the same element with different mass number. |
| Why do Isotopes of particular elements have same chemical properties, but slightly different physical properties | Isotopes of particular elements have same chemical properties because they have same number of electron. They have slightly different physical properties, because they have different number of neutrons |
| What are radioisotopes used for? | To check leaks in oil or gas pipelines |
| How many protons, neutrons and electron, are there in neutral atoms? | In neutral atom, number of positively charged protons in nucleus equals number of negatively charged electrons outside , nucleus |
| What are ions | Ions are charged particles formed by the loss or gain of electrons from atom of group of covalently bonded atoms |
| When are positive ions formed | When 1 or more electrons are lost |
| When are negative ions formed | When 1 or more electron is gained |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Why does General increase in IE, across a period | -Across a period, nuclear charge increases - Electrons removed comes from the same shell. - Force of attraction between positive nucleus and outer negative electrons increases because |
| Why does General increase in IE, across a period | -Across a period, nuclear charge increases - Electrons removed comes from the same shell. - Force of attraction between positive nucleus and outer negative electrons increases because |
| Why does General increase in IE, across a period | -Across a period, nuclear charge increases - Electrons removed comes from the same shell. - Force of attraction between positive nucleus and outer negative electrons increases because |
| Why does General increase in IE, across a period | -Across a period, nuclear charge increases - Electrons removed comes from the same shell. - Force of attraction between positive nucleus and outer negative electrons increases because |
| Why does General increase in IE, across a period | -Across a period, nuclear charge increases - Electrons removed comes from the same shell. - Force of attraction between positive nucleus and outer negative electrons increases because |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| How are principal quantum shells numbered? | Principle quantum shells (symbol n) are numbered according to how far they are from the nucleus. |
| What is the arrangement of electrons in an atom called? | Electron configuration |
| What is the max number of electrons that each principle quantum shells can hold? Shells 1- 4 | Shell 1 - Up to 2 electrons Shell 2 - Up to 8 electrons Shell 3 - Up to 18 electrons Shell 4 - Up to 32 electrons |
| What is the first ionisation energy? | The first ionisation energy of an element is the energy needed to remove one electron from each atom in one mole of atoms of the element in gaseous state to form one mole of gaseous 1+ ions. |
| What is successive ionisation energies? | We can continue to remove electrons from an atom until only the nucleus is left. Sequence of ionisation energies is known as successive ionisation energies. |
| Explain how and why for each element, successive ionisation energies increases? | For each element, successive ionisation energies increases because net positive charge on ion gets greater as each element is removed. As each electron is removed there is a greater attractive force between positively charged protons in the nucleus and remaining negative charged electrons More energy is needed to overcome these attractive forces. |
| Why Size of the nuclear charge influence ionisation energy? (4) | - As atomic number increases, positive nuclear charge in nucleus increases - Bigger the positive charge the greater the attractive force between nucleus and electrons - More energy is needed to overcome attractive forces if an electron is to be removed - Ionisation energy increases as proton number increases |
| Why distance of outer electrons from the nucleus, Influence ionisation energy (3) | - Forces of attraction between positive and negative charges decreases rapidly as distance between them increases - Electrons in shells further away from nucleus are less attracted to nucleus than those closer to the nucleus - Further outer electrons shell is from nucleus, the lower the ionisation energy. |
| Why does shielding effect of inner electrons , influence ionisation energy (5) | - Electrons are negatively charged, so they repel each other - Electrons in full inner shells repel electrons in outershells - Full inner shells of electrons prevent outer electrons prevent outer electrons from feeling full nuclear charge, this is called shielding - Greater the shielding of outer electrons by the inner electrons shells, the lower the attractive force between the nucleus and the outer electrons. - Ionisation energy is lower as the number of full electron shells between outer electrons and nucleus increases |
| How does Spin-pair repulsion, influence ionisation energy? | - Electron in same atomic orbital in a sub-shell repel each other more than electrons in different atomic orbitals - Increased repulsion makes it easier to remove on electrons - First ionisation energy is decreased. |
| How can we use successive ionisation energies ? | - Predict / confirm the simple electron configuration of elements - Confirm number of electrons in outer shell of an element and hence the group to which the element belongs - Deduce which group an element belongs to in Periodic table |
| What are atomic orbitals? | An atomic orbital is a region of space around the nucleus of an atom that can be occupied by 1 or 2 electrons |
| Atomic Orbitals can only hold max 2 electrons, number of orbitals in each sub-shell must be : | S - 1 orbital p - 3 orbitals d- 5 orbitals |
| The first principle quantum level can hold max number (1) of electrons in what sub-shell (2) | First principle quantum shell can hold max 2 electrons in s sub-shell |
| The third principle quantum level can have max of (1) electron, in all the sub-shells. How are they distributed | 2 electrons in s sub-shell 6 Electrons in p sub-shell 10 Electrons in d sub-shell |
| The second principle quantum level can hold max number of (1) electrons, and how are they distributed | 2 electrons in s sub-shell 6 electrons in p sub-shell |
| What is the electronic configuration of potassium? | 1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 |
| What is Spin-pair repulsion | Electrons in same region of space repel each other because they have same charge |
| What is free radical? | A free radical is a species with one or more unpaired electrons |
| Why are Stable metal ions smaller than atoms? | Stable metal ions are smaller than metal atoms because the atoms have lost their outer shell electrons, so the attractive forces between the nucleus and outer electrons are larger. |
| Why do Stable non-metal ions larger than metal atoms? | Stable non-metal ions are larger than metal atoms because the atoms have gained electrons to complete their outer shells, so attractive forces between nucleus and outer electrons is smaller. |
| Why does the atomic radius increases down any group? | Because each successive elements have one more shell of electrons which is further from the nucleus. |
| Why does the atomic radius decrease across any period | - Because of the proton number - The nuclear charge increases by 1, extra electron added goes into same (outer) energy level. - Shielding does not change |
| Why does General increase in IE, across a period influence ionisation energies? | -Across a period, nuclear charge increases - Electrons removed comes from the same shell. - Force of attraction between positive nucleus and outer negative electrons increases. |
| Why does Rapid decrease in ionisation energy between last element in one period and the first element in next period influence ionisation energies? | - Forces of attraction between positive nucleus and outer negative electrons because distance between the nucleus and the outer electrons increases, and shielding of inner shells increases. |
| Why does slight decrease in IE1 between beryllium and boron influence ionisation energies? | - Boron has 1 more proton than beryllium, there is slight decrease in IE1 on removal of outer electrons - beryllium has electron structure 1s^2 2s^2 and boron has electron structure 1s^2 2s^2 2p^1 - Less attractive between 5th electron in boron and nucleus because, distance between nucleus and outer electron increases slightly, shielding by inner shells increases slightly |
| Why does Slightly decrease in EI2 between nitrogen and oxygen influence ionisation energies? | - Oxygen has 1 more proton than nitrogen, electron removed is in 2p sub shell - Electrons removed from nitrogen is from orbital that contains an unpaired electrons - Electrons removed from oxygen is from orbital that contains a pair of electrons - Extra repulsion between pair of electrons in this orbitals results in less energy being needed to remove an electron. - IE1 for oxygen is lower because of spin pair repulsion |
| Nuclear charge is increasing down the group there is less attraction between outer electrons and the nucleus, because : | - Distance between nucleus and outer electrons increases - Shielding by complete inner shells increases |
| What is meant by term stoichiometry? | Stoichiometry is the proportions of reactants and products. A balanced chemical equation can be used to find the stoichiometry of a reaction. |
| What is meant by term stoichiometry? | Stoichiometry is the proportions of reactants and products. A balanced chemical equation can be used to find the stoichiometry of a reaction. |
| What is meant by term stoichiometry? | Stoichiometry is the proportions of reactants and products. A balanced chemical equation can be used to find the stoichiometry of a reaction. |
| What is meant by term stoichiometry? | Stoichiometry is the proportions of reactants and products. A balanced chemical equation can be used to find the stoichiometry of a reaction. |
| What is meant by term relative atomic mass? | The weighted mean mass of an atom of an element relative to an atom of carbon-12 having a mass of exactly 12 units |
| What is meant by term molecular mass? | The weighted average of the mass of a molecule relative to an atom of carbon-12 having a mass of exactly 12 units |
| What is meant by the term relative isotopic mass? | The mass of an atom of an isotope on a scale relative to an atom of carbon-12 having a mass of exactly 12 units |
| What is meant by the term relative formula mass? | The weighted average of the masses of the formula units relative to an atom of carbon-12 having mass of exactly 12 units |
| What is meant by term amount of substance ? | - measured in moles - Based upon the standard count of atoms called Avogadro Constant. - Measured the number of atoms in a substance. |
| What is the Avogadro constant (NA)? | - The number of atoms per mole of substance - Na= 6.02 x 10^23 mol^-1 |
| Define the mole | The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of carbon-12. |
| How can a mass spectrum be used to deduce the relative molecular mass? | The peak with the highest m/z value (The molecular ion peak or M^+ Peak) is caused by the whole molecule after one electron has been knocked off. m/z value of M^+ peak = molecular mass |
| What is meant by the term empirical formula? | The simplest whole number ratio of atoms of each element present in a compound. |
| What is meant by the term molecular formula? | The actual number of atoms of each element present in a compound. |
| What is meant by the term concentration? What equation links concentration and number of moles? | Concentration is the amount of solute (usually in moles) dissolved per dm^3 of solution. C=n/v |
| How do you calculate the amount of a given substance (in moles) using mass and molecular mass? | Number of moles = mass / molecular mass n=m/Mr |
| What equation links volume and number of gaseous moles at room temperature and pressure? | Number of moles = Volume (dm^3) / 24 n=V/24 |
| How many significant figures should calculated results be given to? | Unless stated differently, 3 significant figures. |
| What is meant by term stoichiometry? | Stoichiometry is the proportions of reactants and products. A balanced chemical equation can be used to find the stoichiometry of a reaction. |
| Unified atomic mass | One twelfth of the mass of a carbon-12 |
| Relative atomic mass | Ratio of the average mass of the atoms of an element to the unified atomic mass units |
| Values of the relative atomic mass in the Periodic Table are determined by what... | Determined by using the weighted average mass of the atoms of a particular elements |
| What term do we use for the mass of a particular isotope of an element which has the Avogadros number of atoms (6.02 x 10^23) | Relative isotopic mass |
| How do we find the relative molecular mass | By adding up the relative atomic masses of all the atoms present in one molecule |
| What term do we use compounds containing ions | Relative formula mass |
| Compounds can form crystals which have water as part of their structure. What is this water called? | Water of crystallisation |
| A compound containing water of crystallisation is called? | Hydrated compounds |
| A compound which does not contain water of crystallisation is called? | Anhydrous compounds |
| What is the main use of mass Spectrometry? | Main use of mass spectrometry is in the identification of organic compounds. |
| What is fingerprinting? | Other form of spectroscopy, a substance can be identified by matching its spectrum against the spectra of known substances stored in a database. |
| How is a molecular ion formed? | A molecular ion is formed when 1 electron is removed from a molecule to form an ion with a single positive charge. |
| Fragmentation of a compound in a mass spectrometer causes what? | Fragmentations of a compound in a mass spectrometer causes certain bonds to break |
| The breaking of single bonds such as C-C , C-O or C-N is the most common cause of what? | Fragmentation |
| What does the formula of a compound show us? | Formula of a compound shows us the number of atoms of each element present in one formula unit or one molecule of the compound |
| Explain Avogadro constant | Number of particles equivalent to the relative atomic mass or relative molecular mass of a substance in grams. |
| Define term mole, in terms of Avogardros constant. | A mole is the amount of substance which contains 6.02 x 10^23 specified particles |