S2 - The periodic table and bonding Flashcards
arrangement of elements in the Periodic Table:
-elements are arranged in order of atomic (proton) number (bottom number) and so that elements with similar properties are in columns, known as groups
-elements in the same period group have the same amount of electrons in their outer shell, which gives them similar chemical properties
-elements with the same number of shells of electrons are arranged in rows called periods
-group 1: 1+ ions, 2: 2+ ions, 3: 3+ ions, 5: 3- ions, 6: 2- ions, 7: 1- ions
electronic configuration of the first 20 elements from their positions in the p.t.:
-the electronic configuration of an element tells you how many electrons are in each shell
-for example, sodium has 11 electrons: 2 in its most inner shell, then 8, then 1 in its outermost shell -> you can represent sodium’s electronic configuration as: 2.8.1
-remember-electrons fill the shells closer to the nucleus before filling any further out. 1st shell holds 2 electrons, 2nd and 3rd hold 8
electrical conductivity and the acid-base character of oxides to classify elements as metals or non-metals:
-metals are generally conductive (of electricity)
-non-metals (excluding graphite) are not conductive
-if an element is conductive and its oxide is basic then the element is a metal
-if an element is not conductive and its oxide is acidic then it’s non metal
identify an element as a metal or non-metal according to its position in the p.t:
-metals: elements that react to form positive ions -> majority of elements are metals + found to the left and towards the bottom of the periodic table
-non-metals: elements that do not form positive ions -> found towards the right and top of the periodic table
the electronic configuration of a main group element is related to its positions in the p.t:
-group number: gives number of electrons in outer shell e.g. group 3 has 3 electrons in outer shell
-period number: gives number of electrons shells e.g. period 1 has 1 shell of electrons
why elements in the same group of the p.t. have similar chemical properties:
-number of electrons in outer shell is responsible for the way different elements react
-this means elements with the same number of electrons in the outer shell will undergo similar reactions
-therefore elements in the same group have similar chemical properties
why do noble gases (group 0) not readily react?
-they have 8 electrons in their outer shell (except helium, which has 2)
-they are unreactive and do not easily form molecules, because they have a stable arrangement of electrons
how are ions formed?
-ions: atoms that have lost or gained electron/electrons
-metal reacting with non-metal: electrons in the outer shell of the metal atom are transferred -> metal atoms lose electrons to become positively charged ions + nonmetal atoms gain electrons to become negatively charged ions
-cation: positive ion (+)
-anion: negative ion (-)
charges of ions: metals in Groups 1,2,3 and nonmetals in groups 5,6, and 7 (12)
-Ag+(+ at the top)
-Cu2+
-Fe2+
-Fe3+
-Pb2+
-Zn2+
-H+
-OH-
-NH4+
-CO32-
-NO3-
-SO42-
write formulae of charged ions:
-compound have no overall charge, therefore charges of ions must cancel out
how are ionic compounds formed?
-ionic compounds are formed when a metal and nonmetal react
-ionic bonds are formed by the transfer of electrons from the outer shell of the metal to the outer shell of the nonmetal
-the metal therefore forms a positive ions and the nonmetal forms a negative ion
ionic bonding in terms of electrostatic attractions:
-a giant structure of ions = ionic compound
-held together by strong electrostatic forces of attraction between oppositely charged ions
-the forces act in all directions in the lattice, and this is called ionic bonding
an example is sodium chloride (salt): Na+ (small blue particles) and Cl- (larger green ones)
understand why compounds with giant ionic lattices have high melting and boiling points:
-strong electrostatic forces of attraction between oppositely charged ions
-requires a lot of energy to overcome these forces of attraction
-therefore, compounds with giant ionic lattices have high melting and boiling points
ionic compounds and conductivity:
-ionic compounds do not conduct electricity when solid, but do conduct electricity when molten and in aqueous solution
-as a solid, the ions are in fixed positions so can’t conduct electricity
-when molten or in aqueous solution the ions are free to move carrying charge and conducting electricity
covalent bond formation: occurs in…
-covalent bonding occurs in most non-metallic elements and in compounds of nonmetals
-when atoms share pairs of electrons, they form covalent bonds, these bonds between atoms are strong
covalent bonds in terms of electrostatic attractions: strong bonds…
-strong bonds between atoms that are covalently bonded are the result of electrostatic attraction between the positive nuclei of the atoms and the pairs of negative electrons that are shared between them
dot and cross diagrams to represent covalent bonds:
-hydrogen: 2 hydrogen with one dot and one cross in the middle between them HH
-hydrogen chloride: 1 hydrogen and one chlorine, chlorine has 6 crosses and in between them there is a dot and a cross HCl
-water: 2 hydrogen and 1 oxygen, the oxygen has 4 dots and shares one cross and one dot with both of the hydrogen HOH
-methane: 4 hydrogens surrounding 1 carbon each of them sharing one dot and one cross H
HHCHH
-oxygen: 2 oxygen, one having 4 dots and the other 4 crosses and sharing 2 dots and 2 crosses in the middle OO
-carbon dioxide: 2 oxygens, each having 4 dots surrounding 1 carbon, and two dots and two crosses in between both OCO
explain why substances with giant covalent structures are solids with high melting and boiling points:
-substances that consist of giant covalent structures are solids with very high melting points
-all of the atoms in these structures are linked to other atoms by strong covalent bonds
-these bonds must be overcome to melt or boil these substances
structure diamond: how it influences physical properties, including electrical conductivity and hardness
diamond:
-in diamond, each carbon is joined to 4 other carbons covalently
-it’s very hard, has a very high melting point and does not conduct electricity
structure graphite: how it influences physical properties, including electrical conductivity and hardness + graphene
graphite + graphene:
-in graphite, each carbon is covalently bonded to 3 other carbons, forming layers of hexagonal rings, which have no covalent bonds between the layers -> the layers can slide over each other due to no covalent bonds between the layers, but weak intermolecular forces meaning that graphite is soft and slippery
-one electron from each carbon is delocalised
-> this makes graphite similar to metals, because of its delocalised electrons + it can conduct electricity-unlike a diamond
graphene:
-single layer of graphite
-has properties that make it useful in electronics and composites
structure C60 fullerenes: how it influences physical properties, including electrical conductivity and hardness + carbon nanotubes
C60 fullerene + carbon nanotubes:
-molecules of carbon atoms with hollow shapes
-they are based on hexagonal rings of carbon atoms, but they may also contain rings with five or seven carbon atoms
carbon nanotubes:
-cylindrical fullerenes with very high length to diameter ratios
-their properties make them useful for nanotechnology, electronics and materials
know that covalent compounds do not usually conduct electricity:
-exceptions include: graphite and graphene
