practice questions Flashcards
what shape is buckminsterfullerene molecule?
spherical
give one use of a fullerene
- drug delivery (around the body)
- lubricants
- catalysts
- anti-oxidants
why does propanone have a low boiling point?
the intermolecular forces are weak
explain why graphite is a good electrical conductor; soft and slippery
- in graphite, each carbon atom is covalently bonded to three other carbon atoms
- this leaves one free electron per each carbon atom
- these form a sea of delocalised electrons which can move around the structure and carry the charge
- so graphite conducts electricity
- layered structure of hexagonal rings
- there are no covalent bonds between the layers
- so they can slide over each other, so graphite is soft and slippery
give the meaning of isotopes
atoms with the same number of protons but different number of neutrons
give two reasons why the discovery of gallium helped Mendeleev’s periodic table to become accepted
- gallium fitted in a gap that Mendeleev had left
- gallium’s properties were predicted correctly by Mendeleev
give two observations you could make when a small piece of potassium is added to water
- lilac flame
- effervescence
- potassium melts
- potassium becomes smaller
explain why the reactivity of elements changes going down group 1
- going down the group, reactivity increases
- this is because the size of the atom increases going down the group
- and the shielding effect increases
- this means that the attraction between the positively charged nucleus and negatively electron is weaker
- so it is easier for atoms to lose an electron going down the group
why is oxygen described as being reduced in the reaction between sodium and oxygen?
oxygen gains electrons
explain why sodium oxide has a high melting point
- giant structure
- with strong electrostatic forces of attraction between oppositely charged ions
- so large amounts of energy are needed to break the bonds
name the salt produced by the neutralisation of hydrochloric acid with potassium hydroxide
potassium chloride
explain why alloys are harder than pure metals
- the atoms are different sizes
- so the layers are distorted
- and slide over each other less easily than in pure metals
what are the differences between covalent and ionic bonding?
- in covalent electrons are shared, in ionic electrons are transferred
- in covalent there are intermolecular forces, in ionic there are electrostatic forces of attraction
what did Niels Bohr discover?
electrons exist in shells and orbit the nucleus at specific distances
what is the order of discovery of the sub-atomic particles?
electrons, protons, neutrons
what is the relative mass of a proton?
1
what is the relative mass of a neutron?
1
what is the relative mass of an electron?
very small, close to 0
what is a compound?
different atoms chemically bonded in a fixed ratio
explain why argon does not react with tungsten
- argon is unreactive
- because it has a full outer shell of electrons
why does iodine have a higher boiling point than chlorine?
the forces between iodine molecules are stronger
why does potassium iodide solution conduct electricity?
it contains ions which can move
what are the products of electrolysing potassium iodide solution?
cathode: hydrogen
anode: iodine
what are the physical properties of transition elements?
- high melting points
- high densities
- strong
- hard
what are the chemical properties of transition elements?
- used as catalysts
- form ions with different charges
- form colourless compounds
- low reactivity, react slowly with water
what are the physical properties of group 1 elements?
- low melting points
- low densities
- soft
what are the chemical properties of group 1 elements?
- only from ions with 1+ charge
- very reactive
- form white/colourless compounds
what is meant by a strong acid?
- completely ionises
- when dissolved in water
explain how a covalent bond holds two atoms together
- electrostatic force of attraction between shared pair of negatively charged electrons
- and both positively charged nuclei
what is a compound?
two or more elements that are chemically bonded together
what is the main differences between metals and non-metals?
- metals conduct electricity, whereas, non-metals are generally electrical insulators
- metals also have higher boiling and melting points
- metals are ductile and malleable whereas non-metals are brittle
what does ductile mean?
can be drawn out into wires
what does malleable mean?
can be hammered into shapes without smashing it
what is the name of the elements in Group 0 of the periodic table?
noble gases
describe three other differences between the plum pudding model and the nuclear model of the atom
in the nuclear model:
- the positive charge is all in the nucleus
- the mass is all concentrated in the nucleus
- the electrons and the nucleus are separated
- the atom is mostly empty space
describe the change that Bohr made to the nuclear model
- electrons orbit the nucleus
- at specific distances from the nucleus
why did Mendeleev reverse the order of some pairs of elements?
so their properties matched the rest of the group
which sub-atomic particle has the lowest mass?
electron
describe how the process of distillation shown in figure 2 produces pure water from salt solution
- salt solution is heated
- solution evaporates
- the vapour condenses inside the condenser
- pure water is collected inside the beaker
define mass number
the sum of protons and neutrons
why is the mass number different in the two isotopes?
different numbers of neutrons
explain how evidence from the alpha scattering experiment led to a change in the model of the atom from the plum pudding model
- most alpha particles passed straight through the foil
- so the mass of the atom is concentrated in the nucleus//most empty space
- some alpha particles were deflected
- so the atom has a positively charged nucleus
explain how Chadwick’s work led to a better understanding of isotopes
- Chadwick proved the existence of the neutron
- which was necessary because isotopes have the same number of protons
- but different number of neutrons
explain why sodium oxide has a high melting point
- sodium oxide is arranged in a giant ionic lattice
- strong electrostatic forces of attraction between oppositely charged ions
- requires a lot of energy to overcome these bonds
