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Slide 1

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Chemistry (C2) revision
Yr. 11 mocks…read more

Slide 2

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Structure and bonding…read more

Slide 3

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Chemical bonding
· When two or more elements react together compounds are formed. Atoms of element join together
by sharing electrons or by transferring electrons to achieve stable electronic structures ­ atoms of
noble gases have stable electronic structure
· When atoms of non-metallic elements join together by sharing electrons it is COVALENT
BONDING
· When metallic elements react with non-metallic elements they produce ionic compounds ­ metal
atoms lose electrons to form positive ions, the atoms and the non-metals gain electrons to form
negative ions. Ions had stable electronic structure of noble gas ­ oppositely charged ions attract
one another in ionic compound ­ this is called IONIC BONDING
· Elements in group 1 of periodic table have atoms with 1 electron in their outer shell ­ e.g. sodium
atoms, Na, (electronic structure 2,8,1) form sodium ions Na^+, electronic structure 2,8
· Elements in group 7 of periodic table have atoms with seven electrons in the outer shell ­ e.g.
chlorine atoms (2,8,7) form chlorine ions Cl^- (2,8,8)
· Compound sodium chloride has equal numbers of sodium ions and chlorine ions so we write the
formula as NaCl…read more

Slide 4

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Ionic bonding
· Ionic bonding holds oppositely charged ions together in GAINT STRUCTURES - giant
structures of ionic compounds = very regular because ions all packed together neatly
· Strong electrostatic forces of attraction act in all directions - each ion in giant structure or
lattice is surrounded by ions with the opposite charged and so is held firmly in place
· Sodium chloride contains equal numbers of sodium ions and chlorid3e ions as shown by
formula NaCl - sodium and chloride ions alternate to form a cubic lattice
· Ratio of ions in structure of ionic compound depends on charges on ions - e.g. calcium ions
= Ca^2+ and chloride ions = Cl^- - so calcium chloride contains twice as many chloride ions
as calcium ions and its formula is CaCl2
· Use dot and cross diagrams to represent atoms and ions involved in forming ionic bonds -
in these diagrams only show electrons in outer shell of each atom / ion
· Get diagram…read more

Slide 5

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Formulae of ionic compounds
· Ionic compounds = neutral. If charge of each ion is known in
compound can work out formula by balancing the charges ­ sodium
chloride NaCl (one Na+ for every one Cl^-) but calcium chloride is
CaCl2 (one Ca^+2 ion for every Cl^-)
· Charge on simple ions formed by elements in main groups of periodic
table can be worked out from number of group ­ for transition metals
charge on ions is shown by Roman numeral in name of compound,
e.g. iron(II) sulfate contains Fe^2+
· Some ions made up of more than one element, e.g. carbonate ions =
CO3^2+ and hydroxide ions are OH^- - multiply these ions to write
formula use brackets ­ formula of calcium carbonate CaCO3 and
formula of calcium hydroxide is Ca(OH2)…read more

Slide 6

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Covalent bonding
· Atoms of non-metals need to gain electrons to achieve stable
electronic structures ­ do this by sharing electrons with other atoms,
each shared pair of electrons strongly attracts the two atoms, forming
covalent bonds ­ substances that have atom held strongly together
by covalent bonding are called molecules
· Atoms of elements in group 7 need to gain one electron and to form
single covalent bond and those in group 6 can form 2 bonds­ atoms
of group 5 can form 3 bonds and those in group 4 can form four
bonds
· Covalent bonds act only between 2 atoms it bonds to each other & so
many covalently bonded substances consist of small molecules ­
some atoms that can form several bonds, e.g. carbon, can join
together in giant covalent structures ­ these are sometimes referred
to as macromolecules…read more

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Comments

revizfoshiz

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could hardly see the writing due to the background image

tshepherd671

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great powerpoint

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