OCR 21st Century Science C4
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| Relative atomic mass is the comparison of an atom's mass to []'s (the []est) | hydrogen's--lightest--. |
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| In a periodic table, a [] of elements is a vertical column | group--. |
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| The elements in a group in the periodic table have similar | properties. For example, group 1 contains sodium and other very reactive []s while group 7 contains lithium and other very reactive []-[]s | metals-- non-metals--. |
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| A row of element in the periodic table is called a | period. |
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| Chemical symbol for lithium: | Li |
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| Chemical symbol for sodium: | Na. |
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| Chemical symbol for potassium: | K. |
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| When alkali metals are freshly cut they are | shiny, but they tarnish rapidly in []t []r due to reaction with [] | moist air--oxygen--. |
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| Lithium, sodium and potassium all react vigorously with [] and [] | air and water. |
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| Alkali metals react with water to form [] gas and an [] solution of a [] | hydrogen--alkaline--hydroxide--; the formula is given as H+M[] where M represents a group [] metal | OH--1--. |
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| The group 1 metals are refered to as | alkali metals |
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| A[] []s vigorously react with chlorine to form []less, []ine s[]s with the formula [] | Alkali metals--colourless, crystalline salts--MCl--. |
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| The shiny surface of sodium tarnishes []er than that of lithium, while sodium tarnishes [] than potassium; | quicker--slower; this shows the increasing []ty of the metals as we go down the group | reactivity--. |
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| Because, the alkali metals are so []e, care has to be taken when using them | reactive--. They must not be t[]ed as they will react with [] in [] on the [] | touched--water--sweat--skin--. G[]es may be used and g[]s should be worn | gloves--goggles--.
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| The group 7 elements are also known as the | halogens. |
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| Chemical symbol of chlorine: | Cl. |
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| Chemical symbol of bromine: | Br. |
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| Chemical symbol of iodine: | I. |
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| The halogens consist of []c molecules | diatomic--. |
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| As you go down the group, halogens become [] reactive | less. Flourine, at the top of the group, is the most reactive halogen. It is very dangerous and can cause severe chemical b[]s on contact with skin. | burns--. |
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| The relative reactivity of halogens can be shown by looking at [] reactions | displacement--. |
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| |Displacement Reactions| When chorine (gas or dissolved in water) is added to sodium bromide solution, the [] takes the place of the [] because its more [] and displaces [] from the [] []. | chlorine--bromine--reactive--bromine--sodium bromide--. The solution turns brown, the brown colour being the []d []. The chlorine has gone to form [] [] | displace bromine--sodium chloride--. chlorine + sodium bromide --> | sodium chloride + bromine.
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| Halogens are very []e and p[], hence care must be taken | reactive--poisonous--. Chlorine is used only in a []e []d, iodine should not be handled as it wil damage the []; g[]s may be used, and g[]s should be worn | fume cupboard--skin--gloves--goggles--. |
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| The state symbol (s) means | solid. |
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| The state symbol (l) means | liquid. |
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| The state symbol (g) means | gas. |
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| The state symbol (aq) means | aqueous (dissolved in water). |
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| An atom is a composition of protons and neutrons in a very small central [] and electrons arranged in []s around the nucleus | nucleus--shells--. |
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| Protons and neutrons have the same m[], which is about [] times larger than an electron's. | mass--2000--. An electron's mass is generally taken as 0 for being neglible. |
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| The elements in the periodic table are arranged according to the their [] number | atomic--. |
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| All the atoms of the same element have the same number of p[] | protons. The number of protons will be equal to the number of []s | electrons--. |
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| Some elements emit distinctive []e colours when []ed | flame--heated--, e.g. l[]um, s[]um and p[]um | lithium, sodium and potassium. |
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| The light emitted from a particular element gives a characteristic [] s[] | line spectrum. |
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| Scientists have used line spectra to discover new e[]ts. In fact the discovery of some elements, such as the r[]dium and c[]ium, owuld not have been possible if not of spectroscopy | elements--rubidium--caesium--. The element helium was discovered by studying line spectra emitted by the [] | Sun. |
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| The discovery of some elements depended on the development of new []cal t[]s | practical techniques-- e.g. s[]opy | spectroscopy--. |
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| Electrons are contained in s[]s around the []s, also called []y l[]s | shells--nucleus--energy levels. A shell (or [] level) fills with electrons across a [] | energy--period-- (thus elements in the same group have the same number of electrons in their outer shell, this number being the group number). |
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| Elements in the same [] have the same number of electrons in their outer shell and this number is the [] number | group--group--. |
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| When lithium is added to water it []s, f[]ing steadily and becomes []er until it eventually d[]rs | floats--fizzing--smaller--dissappears--. |
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| Protons has a relative mass of [] unit(s), while neutrons have one of [] unit(s) | 1--1--. The relative atomic mass is thus the number of [] + number of [] | protons--neutrons--. |
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| The relative atomic mass - number of protons = | number of neutrons. Atomic number = number of []s = number of []s | protons--electrons--. |
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| Molten (i.e. melted) compounds of metals with non-metals c[] electricity, which is eevidence that they are mde up of []ed particles called []s | conduct--charged--ions--. |
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| An ion is an [] (or group of []s) which has gained or lost []s and thus has an overall []e | atom--atoms--electrons--charge. |
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| The alkali metals (group 1) form ionic compounds when they react with []-[]s; their ions have a []ive charge of [] | non-metals --positive--1--. For example, sodium forms sodium ions, Na^[] (M^n+ has n electrons [] than an a[] its type) | +--less--atom--. |
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| The halogens (group 7) form ionic compounds when they react with []s; their ions have a []ive charge of [] | metals --negative--1--. For example, chlorine forms chlorine ions, Cl^[] (M^n- has n electrons [] than an a[] its type) | - --more--atom--. |
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| If one knows the charges on the ions in an []ic c[]d, one can work out its formula | ionic--compound--. To do so, simply balance b[]e the positive and negative []es: e.g. calcium has ion Ca^2+ while chlorine has ion Cl^-, meaning the formula is [] | balance--charges--CaCl2[ss]--. |
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| If one has the formula of an []ic c[]d and the charge of one of the two ions, one can work out the charge of the other ion | ionic--compound--. To do so, simply look at what b[]es the c[]es: eg. take Na2O, knowing a sodium ion is Na^+ - the oxygen ion must be [] | balaces--charges-- O^2- --. |
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| As group 7 elements are non-metals, the compounds of halogens with alkali metals are []ic | ionic--. |
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| Solid ionic compounds form c[]s because ions are arrange in a r[]r l[]e | crystals--regular--lattice--. |
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| [] ionic compounds do not conduct electricity as the ions are held firmly in []ce; they cannot [] to conduct the electric current | solid--place--move--. |
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| When an ionic compound melts, the charged ions are free to [] independently in the liquid, meaning that []en ions do [] electricity | move--molten--conduct--. |
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| When a crystal of an ionic compound dissolves, the ions s[]e, meaning that the ions are free to [] inependently in the liquid, so a solution of an ionic compound in water []s electricity | separate-moves--conducts--. |
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| =Line spectra= All atoms give off []t when heated, although sometimes this light is not visible to the human eye. | light--.A p[]sm is used to s[]t the light to form a s[], and each element has a distinctive l[] s[] [#b4#] |
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| The innermost (first) shell can hold up to [] electron while the second shell can hold up to [] | 2--8--; for the first 20 elements, the third shell can hold up to [] | 8--. |
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| An electron configuration of 2 electrons then 8 then 8 would be shown as: 2[]8[]8 | 2.8.8 -- or through dots in circles. [#C6#] |
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| At room temperature and pressure, chlorine's state is [] and is y[]-[] in colour | gas--yellow-green--. At room temperature and pressure, bromine's state is [] and it's []-b[] in colour | liquid--red-brown--. At room temperature and pressure, iodine's state is as a [] and it's colour is a d[] []e | solid--dark--purple--.
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| At room temperature and pressure, Bromine, unlike gas chlorine, is a liquid -- coloured red-brown. When it's a gas, it's []wish-b[] in colour | yellowish-brown--. |
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| At room temperature and pressure, iodine is a dark purple solid, while as a gas it is [] []e | dark purple--. |
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| Group 1 elements are also known as [] me[]s | alkali metals. |
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| Lithium, Sodium, Potassium, Rubidium and Caesium are all in group [] of the Periodic table | 1. |
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| All the alkali metals react v[]ly with cold water. In each reaction [] gas is given off and the metal []de is produced | vigorously--hydrogen--hydroxide--. The state of the alkali metals is obviously [] while the metal hydroxide's are a[] al[]ne []tions | solid--aqueous--alkaline--solutions--. |
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| All the alkali metals react vigorously with cold water. The s[] and vi[] of the reaction increases as you go 1 the group | speed--violence--. This shows the []ty of the alkali metals increases as you go down Group 1 | reactivity--. |
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| When Sodium is added to water, the sodium []s to form a [] that moves around on the s[] | melts--ball--surface--. It []es []ly, and the hydrogen produced may b[] with an []e []e before the sodium d[]s | fizzes rapidly--burn--orange flame--disappears--. |
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| When potassium is added to water, the metals []s and []s--it moves around []ly on the []e of the water--the hydrogen []es []tly | melts--floats--quickly--surface--ignites instantly--. The metal is also set on []e, with s[]s and a l[] flame; there is sometimes a small e[] at the end of the reaction | fire--sparks--lilac--explosion--. |
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| lithiu + water → | lithium hydroxide + hydrogen, or as a chemical equation: | 2Li(s) + 2H₂O(l) → 2LiOH(aq) + H₂(g) |
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| sodium + water → | sodium hydroxide + hydrogen, or as a chemical equation: | 2Na(s) + 2H₂O(l)→ 2NaOH(aq) + H₂(g) |
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| potassium + water → | potassium hydroxide + hydrogen, or as a chemical equation: | 2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g). |
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| The trend in reactivity for halogens (decreasing as you descend) can be shown in []ment reactions where the [] reactive element displaces the [] reactive one | displacement--more--less--, and is evident in their reactions with [] m[]s and with i[] | alkali metals--iron--. |
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| Because the halogens are very []e and []us, care must be taken when using them | reactive--poisonous--. Chlorine is used only in a f[] c[]. Iodine should not be h[]ed (it will damage the []n) | fume cupboard--handled--skin--. G[]s may be used and g[]s must be worn | gloves--goggles--.
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| The chemical formua for Hydrogen: | H₂. |
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| The chemical formula for chloride is [] as it's an []n | C⁻ as it's an anion-- (though it may not always be shown as such, e.g. 2NaCl). The chemical formula for bromide is [] while the chemical formula for iodide is [] | anion-- Br⁻ -- I⁻ --. Chlorides, bromides and iodides made up the group known as the | halides.
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| Atoms of each element have a different [] number (i.e. number of []s), | proton--protons--; also called [] number | atomic--. |
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| Arranging the elements according to their atomic number gives []g patterns in the []s of elements | repeating--properties--; each element in the periodic table is placed in a [] with those of similar properties | column |
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