GCSE Chemistry C4 (OCR)

Questão	Responda
Atoms of each element have different ______ numbers.	Proton.
Why is arranging elements based on their proton number beneficial?	...because it gives repeating patterns in the properties of elements.
What were the significant stages in the history of the development of the periodic table?	- Chemists compared the masses of atoms with the mass of the lightest, hydrogen. This is called the relative formula mass. -Dobereiner: Groups of 3 had similar properties. RAM of element 2 = Mean of RAM of 1 + 3. Newlands: In order of RAM, every 8th element had similarities. Only worked for 1-16. Mendeleev: RAM, leaving gaps for undiscovered elements.
How did Mendeleev use his Periodic Table to predict the existence of unknown elements?	He looked for gaps within the expected similarities.
How can you use the Periodic Table to identify the names, symbols, relative atomic masses and proton numbers of elements?	Top No. = Relative Atomic Mass Letter = Symbol Word = Name Bottom No. = Proton Number
What is each vertical column of the Periodic Table?	A group.
What are the chemical symbols for Lithium, Sodium, and Potassium? What are these known as?	Lithium = Li Sodium = Na Potassium = K These are the Alkali Metals. They react with water to form alkaline compounds.
What happens to a freshly cut alkali metal?	They are shiny when freshly cut, but tarnish rapidly in most air due to a reaction with oxygen.
How do Lithium, Sodium, and Potassium react with cold water?	Lithium: Floats, fizzes gently, disappears. Sodium: Skids, fizzes, disappears. Potassium: Catches fire, moves quickly, disappears.
When the alkali metals react with water, what do they form?	They form their hydroxides (eg. Sodium hydroxide) and hydrogen. The formula is MOH
When the alkali metals react with chlorine, what do they form?	They form their chlorides (salts), (eg. Sodium chloride). The formula is MCl
Do the alkali metals become more or less reactive as the group is descended? What is the evidence for this?	More reactive. Melting points and boiling points decrease as the group is descended.
What are the main hazard symbols?	Explosive, harmful, toxic, corrosive, oxidising, highly flammable.
What precautions should be taken when working with Group 1 metals and alkalis?	Use forceps and wear goggles.
What are the chemical symbols for the Group ___ elements chlorine, bromine, and iodine?	7 Chlorine = Cl2 Bromine = Br2 Iodine - I2
What state are the Halogens in at room temperature and pressure?	Chlorine: Gas Bromine: Liquid (+ Vapour) Iodine: Solid (+ Vapour)
What colour are the Halogens at room temperature and pressure? And as gasses?	Chlorine: Green, Green Bromine: Red, Red-Brown Iodine: Grey, Purple
What do the Halogens consist of?	Diatomic molecules, so the atoms are joined in pairs.
Do the Halogens become more or less reactive as the group is descended? What is the evidence for this?	Less reactive. The boiling and melting points increase as the group descends.
How can a trend in reactivity be shown by the Halogens?	Iodine solution can be used to treat infections, but chlorine solution is much too reactive to do this. Iron glows strongly in chlorine gas, but doesn't glow in iodine vapour. Displacement reaction shows that Chlorine solution will displace bromine from its solution, so bromine will form and the solution will turn red.
What safety precautions need to be taken when working with Halogens?	Wear eye protection, wear chemical resistant gloves, make the reactions in a fume cupboard.
What are the formulae of hydrogen, water, and halogen molecules?	Hydrogen = H2 Water = H20 Halogens = Cl2, Br2, I2
What are the formulae of the chlorides, bromides, and iodides (halides) of Group 1 metals?	Chlorides = LiCl, NaCl, KCl Bromides = LiBr, NaBr, KBr Iodides = LiI, NaI, KI
How do you write word equations for reactions of alkali metals and halogens?	Eg. Cl2 + Br ---> BrCl2
What is the structure of an atom?	The protons and neutrons are in the nucleus, with the electrons arranged in shells around the nucleus.
What are the relative masses and charges of protons, neutrons, and electrons?	Neutron = 1, 0 Proton = 1, +1 Electron = Negligible, -1
In any atom, the number of _______ equals the number of ________.	Electrons Protons
How are the elements in the Periodic Table arranged	In order of proton number.
When heated, what do some elements emit? (Eg. Lithium, Sodium, Potassium).	Distinctive flame colours.
What does the light emitted from each element give?	A characteristic line spectrum.
What has the study of spectra helped chemists to do?	Discover new elements.
What did the discovery of some elements depend upon?	The development of new practical techniques, such as spectroscopy.
How can you use the Periodic Table to identify the number of protons, neutrons, and electrons in an atom?	Proton No. = No. of protons Top No. = No. of electrons in each shell No. of protons = No. of neutrons
How can you represent the arrangements of atoms?	2.8.1 2 full shells of electrons, 1 electron on the outer shell.
What does each shell fill with?	Electrons
What do the outer shells of elements in the same group have in common?	They have the same number of electrons.
What are the chemical properties of an element determined by?	The number of electrons in the outer shell. Eg. One or two = Metal. Two + = Non-Metal
Molten compounds of metals with non-metals ______ _______. What is this evidence for?	Conduct Electricity. They are made up of charged particles called ions. In a solid, the particles cannot move towards the electrode, so the compound cannot conduct electricity.
What happens during electrolysis?	The negative electrode attracts the positive ions. The positive electrode attracts the negative ions. The ions lose their charges and turn back into atoms.
What is an ion?	An atom that has gained or lost electrons, and so has an overall charge.
How can you account for the charge on the ions of Group 1 and Group 7 elements?	The ions of group 1 elements are positive, because they lose an electron. The ions of group 7 elements are negative, because they gain an electron.
How can you work out the formulae of ionic compounds given the charges of the ions?	The charges have to cancel each other out.
How can you work out the charge on one ion given the formula of a salt and the charge on another ion?	The charges have to cancel each other out.
Compounds of Group 1 metals with Group 7 elements are _____.	Ionic.
What do solid ionic compounds form? Why?	Crystals, because the ions are arranged in a regular lattice.
What happens to the ions when an ionic crystal melts or dissolves in water?	-
When and why do ionic compounds conduct electricity?	-

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