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22 Cards in this Set
- Front
- Back
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Mendeleev - 1871
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Constructed periodic table according to: RAM Similarity between elements (Groups) |
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Building Atoms
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Electrons have a negative charge and almost no mass - electrons whiz around the nucleus in shells Protons are positively charged and have the same mass as a hydrogen atom (1) Neutrons have no charge and the same mass as a proton |
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Nucleus
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Protons and neutrons are found in a bundle at the centre of each atom. Nucleus diameter is about 1/1000th of the whole atom but contains almost all the mass of the atom. |
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RAM (Relative Atomic Mass)
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Number of protons + Number of neutrons
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Electron arrangement
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2,8,8...
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Shells and levels
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The shell that an electron is in represents the energy level of the electron (also determines the colour in a line spectrum) THE CLOSER THE ELECTRON IS TO THE NUCLEUS, THE LOWER THE ENERGY LEVEL OF THE ELECTRON. |
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Inert element
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An element that does not react with any other elements e.g. Argon
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Trends
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Changes in properties across a period
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Groups
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Elements with 1,2 or 3 electrons in their outer shell are metals Elements with 5,6, or 7 electrons in their outer shell are non-metals Elements with 8 electrons in their outer shell are inert gases |
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Group 1
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THE ALKALI METALS - soft - can be cut easily with a knife - conduct electricity - malleable - shiny and silver when cut - corrode/tarnish when reacting with oxygen - metals burn with brightly coloured flames - melting points decrease doing down - no. of atoms decrease going down - energy level increases going down |
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Group 1 Reactions
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Alkali + Water = Hydrogen + Alkali Hydroxide - there can also be violent reactions e.g. Potassium - purple flame |
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Reactivity
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The further the single outer electron is from the nucleus, the easier the atoms find it to combine with other elements to form a compound SO it's reactivity increases.
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Group 7
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THE HALOGENS - Fluorine (F)very pale yellow - Chlorine (Cl) pale green - Bromine (Br) reddish brown gas and dark-red brown liquid - Iodine (I) purple gas and dark grey solid - Astatine (As) most rare element on Earth. Never been seen in enough quantities to describe its appearance. |
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The Halogens
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They are diatomic molecules Melting point increases as you go down All have 7 electrons in their outer shells Make salts |
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Patterns in group 7
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All very reactive React with most elements and compounds Their vapours are very hazardous, corrosive and toxic React violently with alkali metals and other metals to form compounds called halides. Halogens become less reactive going down. |
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Displacement reactions
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One halogen will take down the place of another of its compounds.
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Non-metals
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The smaller atoms that combine most readily with other elements Going down the halogen group, the number of shells increases and the outer shell gets further from the nucleus. Therefore, the reactivity of the halogens decreases down the group |
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Ionic Compounds
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Group 1 and Group 7 elements are all ionic compounds as they are all made up of ions (charged particles) Ionic compounds are made up of positively charged and negatively charged ions Positive ions are atoms that have lost electrons |
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Group 1 and Group 7
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- colourless - crystalline solids - high melting points - conduct electricity when liquids Electric current is produced when charged particles move through a substance. |
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Forming ions
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When a metal atom forms a positive ion, it loses the electrons from its outer shell. When a non-metal atom forms a negative ion, it gains an electron in its outer shell. |
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Lattice
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Ionic compounds (e.g. sodium chloride) form crystals which have a regular shape. In the crystals the ions pack together in a regular pattern repeated over and over called a crystal lattice. |
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Breaking the lattice
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As a solid, ions are fixed in the lattice. When the substance is melted, the ions become free to move. When an ionic compound dissolves in water, the ions leave the lattice. They are separated by water molecules and can move freely. When an electric current is passed into a liquid ionic compound/solution, the charged ions move to the electrodes and complete the circuit. This is why ionic compounds conduct electricity when it is liquid/in a solution. |
