Elements are pure substances containing one type of atom – found on the Periodic Table. The atomis the smallest part that retains all the properties of that element.
Octet rule: atoms react to acquire a full outer shell: • Give away an e- to another atom. • Take an e- from another atom. • Share an e-with another atom. Ionic bond Covalent bond An ION is an atom that has lost or gained an electron. H : neutral atom H+ : positive cation H- : negative anion
+1 +3 -3 -2 -1 +2 +4/-4 Remember: The number of the column is equal to the valence electron number. Know that and you figure out the number of electrons lost or gained – the ionic charge
Ionic NaCl Covalent HCl A compound has different characteristic properties than the atoms which form it.
Ionic Compounds Contain a METAL and a NON-METAL atom. Formed by TRANSFERING valence electrons to fill outer shell – octet rule. • A formula unit is the smallest unit of an ionic compound. Metal + Non-metal = ionic bonding
Writing Rule 1: Write the symbol of the metallic element first. Beryllium combines with Chlorine + 2 - 1 Be Cl Rule 2: Place the combiningcapacityof one element as a subscript of the other element.
Rule 3:Leave subscripts with a value of 1 out. Be Cl2 1 • Two Naming rules: • Write the full name of the metal ionfirst. • Name the non-metal iondropping the last • part of the name and adding the suffix “ide”. beryllium chlor ide
Rule 4: Reduce the subscripts if possible. Magnesium combines with Sulfur + 2 - 2 Mg S MgS magnesium sulph ide
Transition metals can give away different numbers of electrons. To avoid confusion: Brackets are used to show how many electrons the Transition metal is giving away.
Iron (II) chloride Iron (III) chloride + 2 - + 3 - 1 1 Fe Cl Fe Cl FeCl2 FeCl3
Write the name of the ionic compound: +4 -2 Remember: Always look at the anion to see if it has been reduced. If it has, so has the metal. - + Pb O PbO 2 1 lead oxide (IV)
Polyatomic Ions(poly = many) Groups of covalently bonded atoms that act as ionsin ionic bonding. Polyatomic ions function as one unit with one charge – lose or gain electrons. NEVER change the subscripts of polyatomic ions. Al(C2H3O2)3
Write the name of the ionic compound: + - 1 Al C2H3O2 Al(C2H3O2) 3 aluminum acetate
Ni(NO3)2 • magnesium sulfate • KMnO4 • iron (III) hydroxide • Ca(C2H3O2)2 • silver chromate • PbCO3 • tin (IV) sulfate • Na2HPO4 • ammonium nitrite nickel (II) nitrate MgSO4 potassium permanganate Fe(OH)3 calcium acetate Ag2CrO4 lead (II) carbonate Sn(SO4)2 sodium hydrogen phosphate NH4NO2
Covalent Compound Contain two or more NON-METAL atoms. Formed by SHARING valence electrons to fill outer shell – octet rule. • A molecule is the smallest unit of a covalent compound. Non-metal + Non-metal = covalent bonding
Step 1: firstnon-metal is named with a prefix to show the number of atoms. We do not use “mono” for the first non-metal. Step 2: secondnon-metal is named with a prefix AND with the “ide” ending. N O 2 4 nitrogen oxide di tetra dinitrogen tetroxide
Writing formulas Step 1: Write the symbol of each element. Step 2: Use a subscriptto show the number of each type of atom given by the prefix. Do not reducecovalent formulas. di phosphorus oxide penta PO 2 5
Does it have a metal? YES (ionic) Is it a transition? NO (covalent) Polyatomic • Find charges • Reverse Criss-cross • Don’t change ending • NO charges • NO criss-cross • Use prefixs • Ends in “ide” Fe(NO3)2 iron (II) nitrate NO YES OCl2 oxygen dichloride • Find charges • Criss-cross • Ends in “ide” • Find charges • Reverse Criss-cross • Use Brackets • Ends in “ide” MgCl2 magnesium chloride CuCl2 copper (II) chloride
Many reactions are similar • Chemists have classified5 types of reactions BIG PICTURE IDEA: • If you know the reactants- you can guess the typeof reaction AND predict the products
Synthesis A + B C Decomposition C A + B Single replacement A + BC B + AC Double replacement AC + BD AD + BC Carbon Combustion CxHy + O2 CO2 + H2O
Diatomic Elements: Elements that are most commonly found in a covalent bond with itself. I Have No Bright Or Clever Friends I2H2N2Br2 O2Cl2F2
Explain the difference between isotope and radioisotope • Explain average atomic mass using isotopes and their relative abundance Additional KEY Terms Radioactive decay Half-life
The atomic number (Z) is the number of protons in the nucleus of an atom - identifies an element. The atomic mass (A) is the number of protonsplus the number of neutrons.
Isotopes: Atoms with the but a different number of neutrons. same number of protons Hydrogen Atomic Mass = 1 Atomic Number = 1 Deuterium Atomic Mass = 2 Atomic Number = 1 Atomic mass is actually an average of isotopes of an element based on relative abundance in nature
Mass spectrometer determines the mass of individual atoms or isotopes. Sends atoms through a magnetic field which bends their paths. The heavier the atom – the less it bends
Potassium isotopes: 1. 19 protons and 20 neutrons - mass number of 39 (potassium-39 39K) 2. 19 protons and 21 neutrons - mass number of 40 (potassium-40 40K) 3. 19 protons and 22 neutrons - mass number of 41 (potassium-41 41K)
Magnesium exists as three isotopes in the world: 78.99% is 24Mg (23.985 μ) 10.00% is 25Mg (24.986 μ) 11.01% is 26Mg (25.982 μ) Calculate the average atomic mass of magnesium: (0.7899)(23.985 μ) = 18.95 μ + (0.1000)(24.986 μ) = 2.499 μ = 24.31 μ (0.1101)(25.982 μ) = 2.861 μ
helium 5He 6He The nucleus of some isotopes are unstable and break apart over time - radioactivity.
Radioisotopes - unstable nuclei releasing energy and/or particles. Release of energy is called radioactive decay. Half-life- amount of time it takes for half the radioisotope to be converted into another particle. Atoms may be converted into another isotope or a completely different element
Many different types of decay exist: alpha decay, beta decay, gamma decay
CAN YOU / HAVE YOU? • Explain the difference between isotope and radioisotope • Explain average atomic mass using isotopes and their relative abundance Additional KEY Terms Radioactive decay Half-life