Chemical Bond: is a strong attractive force between atoms or ions in a compound. Drawn as a stick or dots of electrons
Electrons bond Valence electrons: electrons in the outer shell or orbital Octet rule: most atoms prefer to have 8 electrons in their outer shells :
Chemical formula Chemical formula: for a compound reveals the elements and their ratios in that compound Atoms are chemically stable when their outer shells are full NaClCO CaCl 2 ZnO CO 2 Fe 2 O 3 FeO
Ions Ionic bond: a force of attraction between two oppositely charged ions Ions: are charged particles that form when atoms gain or lose electrons These atoms are said to have charges Calculate charges by subtracting the number electrons of from the number of protons
Anion Atoms that gain electrons form negative ions Anion: Negatively charged ion
Cation Atoms that lose electrons form positive ions Cation: positively charged ion Cats are positively cwazy
Ions Charged ions that bond form a neutral compound as in salt Na + Cl - Energy is required and can either be given off or absorbed when electrons move In ionic compounds the ions will often disassociate in water Ions are important in your nerve and muscle cells – often called electrolytes
Covalent bonds Covalent bonds: Atoms share electrons Molecules are formed from at least two covalently bonded atoms Water has a covalent bond :.
Covalent Bond Between nonmetallic elements of similar electronegativity. Stable non-ionizing particles, they are not conductors at any state Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC
Oxidation numbers Oxidation number: shows the combining ability of an element in a compound Na +1Mg +2 Cl –1B +3 Some elements have more then one oxidation state Fe, Cu, Cr, Pb, Sn We must indicate the oxidation state when writing these compounds or elements Fe (III), Cu (II), Sn (II),
Naming Covalent Compounds Covalent compounds are named by adding prefixes to the element names. The compounds named in this way are binary covalent compounds. ‘Binary’ means that only two atom are present. ‘Covalent’ (in this context) means both elements are nonmetals. A prefix is added to the name of the first element in the formula if more than one atom of it is present. (The less electronegative element is typically written first.) A prefix is always added to the name of the second element in the formula. The second element will use the form of its name ending in ‘ide’.
Naming Covalent Compounds Prefixes SubscriptPrefix 1mono- 2di- 3tri- 4tetra- 5penta- SubscriptPrefix 6hexa- 7hepta- 8octa- 9nona- 10deca- Note: When a prefix ending in ‘o’ or ‘a’ is added to ‘oxide’, the final vowel in the prefix is dropped.
Naming Binary Covalent Compounds: Examples N 2 S 4 dinitrogen tetrasulfide NI 3 nitrogen triiodide XeF 6 xenon hexafluoride CCl 4 carbon tetrachloride P 2 O 5 diphosphorus pentoxide SO 3 sulfur trioxide 1mono 2di 3tri 4tetra 5penta 6hexa 7heptaa 8octa 9nona 10deca * Second element in ‘ide’ from * Drop –a & -o before ‘oxide’
Writing formulas 1.Symbol with a positive oxidation number is first (metals always have positive oxidation numbers) 2.Symbol with negative oxidation number 3.Write subscripts so oxidation number of the compound totals zero Use parantheses around polyatomic ions if using multiples of these
Polyatomic A group of covalently bonded atoms which have charge. Usually negatively charged Treat polyatomic ions as if they are one thing, don’t mess with their subscripts.
Naming Write the name of the positive ion Write the root of the negative ion-( ox, flor, chlor, iod,etc.) and add ide. For polyatomics just write the name of the ion For multivalent metals tell valence state using roman numerals in paranthesis. Ex. Iron (II) chloride