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c2 Flashcards

(90 cards)

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1
Q

who created the periodic table which is close to the modern periodic table

A

Dimitri Mendeleev

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2
Q

what did Mendeleev do to create the periodic table

A

started by arranging elements in increasing atomic weight but altered to make elements with similar properties in the same group. predicted that there was some undiscovered elements which hadn’t been discovered and placed them where they should be.

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3
Q

why did scientists accept Mendeleev’s periodic table

A

as the predictions that he made where correct, making scientists accept his periodic table.

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4
Q

what are the differences between Mendeleev’s periodic table and the modern periodic table

A

the modern periodic table is arranged in atomic number (number of protons) which hadn’t been discovered meaning some elements that where isotopes where in the wrong place however his prediction through properties increased the accuracy of this. Also group 0/ noble gases weren’t fully discovered

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5
Q

do metals and non metals form ions with positive or negative charges

A

metal - ion = positive
non-metal - ion = negative

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6
Q

what is ionic bonding

A

ionic bonding is where each particle form a full outer shell by either losing or gaining an electron, between a metal and a non metal

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7
Q

how is ionic bonding represented

A

dot and cross diagram

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8
Q

what type of structure do ionic compounds have

A

a regular lattice structure

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9
Q

whats a regular lattice structure

A

a regular structure which has very strong electrostatic forces of attraction between oppositely charged ions in all directions

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10
Q

how is an ionic compound represented

A

a ball and stick model

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11
Q

what are the properties of ionic compounds

A

high melting and boiling points due to strong attraction between ions, takes a lot of energy to break these attractions
don’t conduct electricity as the ions are fixed in place and can’t move, but when compound melts or dissolved in water the ions are free to move and will carry electric charge.

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12
Q

whats covalent bonding

A

two atoms (non-metals) share electrons, e.g. H2O, oxygen needs two more atoms and the hydrogen needs 2 electrons. so the hydrogen combines to oxygen each gaining an electron, forming two single covalent bonds

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13
Q

how do you represent covalent bonds
features of covalent bonds

A

dot and cross diagrams and displayed formulas
low melting and boiling points weak intermolecular forces are easy to break between molecules, don’t conduct electricity

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14
Q

strength of bonds for covalent bonding

A

strong because there’s a strong electrostatic attraction between the positive nuclei and the negative of the electrons

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15
Q

whats a simple molecular force

A

substances formed with covalent bonds usually have simple molecular structures. there is the covalent bonded molecules connected with weak intermolecular forces

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16
Q

what are the features of simple molecular substances

A

low melting and boiling points as the weak intermolecular forces are easy to break. most are gases or liquids at room temperature. don’t conduct electricity as they don’t have free electrons or ions

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17
Q

whats a giant covalent structure

A

many covalent bonds bonded together to form a structure

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18
Q

features of giant covalent structure

A

very high melting and boiling points. dont conduct electricity, not even molten. with some exceptions

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19
Q

whats graphite

A

sheets of carbon which are free to slide over each other. slippery layers and can be rubbed off onto paper (pencil).

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20
Q

features of diamonds

A

very hard, ideal cutting tool, strong covalent bonds take a lot of energy to break meaning there’s a very high melting point

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21
Q

features of graphite

A

high melting point as bonds are difficult to break. only 3 of carbons 4 electrons are used, this means there’s lots of delocalised(free) electrons, meaning graphite can conduct electricity

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22
Q

whats graphene and features

A

a single sheet of graphite, very strong covalent bonds sop high m.p, very good at conducting electricity

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23
Q

whats fullerene

A

another form of carbon, arranged in hexagon rings which combine to form a hollow ball

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24
Q

features of fullerene

A

they have delocalised electrons so they conduct electricity, pretty high melting and boiling points however not as high as graphite and graphene

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25
features of nanoparticles
very very small - bigger than an atom and molecules but smaller than most other things. Have a high surface area to volume ratio.
26
what are nanoparticles used for
nanoscience - they have a high surface area to volume ratio, it means that they are good catalysts. they are also useful for sun-cream and deodorant's as they don't leave a white mark but cover a high area, nanomedicine as the particles are so small that they can deliver medical drugs inside the cell
27
whats a negative about nanoparticles
the way they affect the body isn't fully understood, some people are worried that it affects human health negatively for cosmetics, also unknown impact on the environment when nanoparticles enter the sea
28
what are nanotubes
a type of fullerene arranged in tubes,
29
what are polymers and how are they formed (reaction)
formed when lots of monomers join together in a chain. This reaction is called polymerisation which requires high pressure and a catalyst.
30
whats an example of a polymer
plastic
31
what do the properties depend on for polymers
forces determine the properties, depending on how strong the covalent bonds between the chains are.
32
what are the properties of a polymer if there is weak forces
will be able to stretch easily and will have a low melting point
33
what are the properties of a polymer if there is strong forces
higher melting points, rigid ans cant be stretched
34
what do the properties of materials depend on
the structure and bonding of the atoms, how they are arranged and the strength of bonds to other particles
35
what are the features of metals/ metallic bonding
high melting and boiling points and high density. strong attraction between delocalised electrons and closely packed positive ions causing lots of energy required to break these bonds. strong, bendy and malleable (can be hammered into different shapes) conduct heat and electricity due to the delocalised electrons able to carry the energy through the metal they react with oxygen to form metal oxides can be mixed with other elements to make alloys which adapt for certain jobs. For example they can be stronger, more malleable or more corrosion resistant
36
whats an alloy
two or more elements with at least one being a metal
37
whats metallic bonding
bonding between two metals which share electrons in a sea of delocalised electrons which can carry charge and thermal energy
38
what affects the melting and boiling points of a element
type of structure and bonding. the stronger the attraction between a bond requires more heat energy to break these bonds.
39
b.p for simple covalent bond
low
40
b.p for metallic bond
high
41
b.p for ionic bond
high
42
b.p for giant covalent bond
high
43
what does it mean if a substance is pure
means it is only made up of one element
44
what is a substance called if it is made up of more than one element
a mixture or that its chemically impure
45
how can you test weather a element is pure or not
you can base something being pure from expected melting and boiling point. If a substance is impure the melting point will be too low - e.g. ice -2 and a boiling point being too high - e.g. water 101. You can also tell if an elements impure by heating a substance up. the different components will melt or boil at different temperatures, the mixture will melt over a range of temperatures
46
what is distillation used for
to separate mixtures that contain liquids
47
what are the two types of distillation
simple and fractional distillation
48
whats simple distillation used for with example
used to separate out different solutions with very different boiling points (e.g. a solid and a liquid - saltwater)
49
how do you use simple distillation using saltwater as an example
water has a lower boiling point than salt. This means you can heat the water which goes into a condenser once boiled, cooling down the water vapour and turning it back into water as a pure liquid form. You will be left with salt in the flask and pure water in the beaker
50
whats the problem with simple distillation and how do you overcome this problem
you can only use simple distillation when you have two elements with two very different boiling points. when you have multiple elements with similar boiling points you use fractional distillation.
51
how do you use fractional distillation
put mixture in flask, attaching a fractioning column above the flask. Gradually heat the flask. the first solution with the lowest boiling point will evaporate first and will reach the top of the column and diffuse into the condenser. Other solutions might also evaporate but the top of the column is the coolest part so it will just run back down into the flask. Raise the temperature for the next temperature and collect the solution and repeat until all solution is gone from the flask
52
when is filtration used
to separate a liquid from an insoluble solid
53
how do you do filtration
place filter paper above a flask and let the liquid drip into the flask, you will be left with liquid in the flask and the solid left in the filter paper.
54
when is crystallisation used
to separate a soluble solid from a solution
55
how do you use crystallisation
pour solution into dish and place dish above heat source. when some of liquid solution has evaporated remove dish and let it cool, will start to form crystals as it becomes insoluble and you will be left with the solid
56
what is paper chromatography used for
to test weather a substance is pure or impure, used to separate mixtures of soluble substances in a liquid
57
what are the two phases of chromatography
the mobile (what moves, e.g. liquid) and stationary phase (what remains stationary, e.g. paper)
58
why use pencil to mark the line
pencil is insoluble, if you use ink the ink might raise with the solvent
59
how is paper chromatography performed with ink
you draw a pencil line towards the bottom of the chromatography paper. mark the ink on the pencil line and place the solvent up to the pencil line. the solvent will raise and so will the ink, if multiple dots are produced means that more than one ink was produced if not there's only one type of ink for that colour
60
whats the stationary and mobile phase for paper chromatography
the paper is the stationary phase and the solvent is the mobile phase
61
how do you work out the Rf value
distance traveled by solute (from pencil line) / distance travelled by solvent (from pencil line)
62
why does rf value need to be calculated
to be able to identify the substance
63
whats relative atomic mass
the bigger number of the two numbers represented on the periodic table average mass of all the isotopes of that element
64
whats relative formula mass and how is it represented
all the relative atomic mass of a compound added together, its represented by Mr
65
whats relative formula mass of MgCl2 mg = 24.3 cl = 35.5
95.3
66
whats molecular formula and empirical formula
molecular formula is the actual number of atoms in an element empirical formula is the simplest ratio of atoms in an element
67
whats the empirical formula for C6,H12,O6
CH20
68
whats the molecular formula of CH3 which has an mr of 30
C2H6
69
whats empirical formula of of sulfur and oxygen make sure you prove it sulfur = 50.05% oxygen = 49.5%
sulfur:oxygen 1:2
70
which number is the mass number and what does it represent
total no. of protons and neutrons in an atom
71
whats the atomic number and what does it represent
smaller number, no. of protons
72
what do elements in the same period have
the same number of shells
73
what do elements in the same group have
the same amount of electrons in the outer shell
74
whats more reactive, metals or non-metals
metals
75
an oxygen atom has 6 electrons and gains 2 electrons, what will the charge now be
2-
76
whats the electron structure of nitrogen ( atomic number of 7 and mass number of 14)
2,5
77
whats an ion
an element which gains or loses electrons is an ion
78
formula for hydroxide ion
OH-
79
formula for sulfate ion
SO4 2-
80
formula for nitrate ion
NO3-
81
formula for carbonate ion
CO3 2-
82
formula for ammonium ion
NH4 +
83
what are the features of an alloy
different sized atoms mean the alloy is no longer in a regular structure. This means that the layers of atoms are no longer able to slide past each other and are no longer malleable
84
whats a molecule with example
something made from 2 or more atoms that are chemically bonded e.g. O2
85
whats a compound with example
something with 2 or more elements that are chemically bonded e.g. NaCl
86
whats a mixture with example
a mixture contains 2 or more substances that aren't chemically bonded e.g. air contains many different compounds/molecules
87
whats chemical analysis
instruments and methods used to separate, identify and quantify different substances e.g. paper chromatography, filtration etc.
88
whats a pure substance
a substance which only contains one type of compound/ element
89
how can you tell a pure and impure substance
a pure substance boils and melts over a specific temperature an impure substance melts and boils over a range of temperatures e.g. starts melting at 36 degrees and finishes at 43 degrees
90
whats a formulation
mixtures that have been prepared using a specific formula with a precise amount of different components with the overall mixture performing a particular function

Chem revision (7 decks)

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