The Elemental Dating Game Ionic & Molecular Compounds

Compounds compounds are chemical substances made up of 2 or more elements that are chemically bonded together in fixed proportions compounds are formed by chemical reactions elements form compounds to be more stable chemical bonds form when the atoms of an element gain, loose or share electrons ionic compounds - electrons are transferred between atoms molecular compound – formed if electrons are shared between atoms

all compounds have a name AND a chemical formula e.g. water is H20 e.g. table salt (sodium chloride) is NaCl e.g. baking soda (sodium bicarbonate) is NaHCO3 the chemical formula uses letters and numbers to represent the composition of the compound e.g. water is made up of 2 atoms of hydrogen combined with 1 atom of oxygen

e.g. H2O(l) is liquid water NaCl(aq) is salt dissolved in water we can show the state of the compound at room temperature is also shown in the formula s = solid l = liquid g = gas aq = aqueous (dissolved… in solution) e.g. H2O(l) is liquid water NaCl(aq) is salt dissolved in water

Ionic Compounds atoms of element are neutral (# protons = # electrons) when an atom gains or looses an electron it becomes a negatively or positively charged ION electrons are transferred from metal atom leaving a + charged ion... to the non metal atom leaving a – charged ion Cl– Na+

→ + ionic compounds involve metals AND non metals metallic ions have a + charge non metallic ions have a – charge ionic compounds form because there is an attraction between ions which have opposite charges e.g. NaCl – sodium chloride → + Cl– Na+ NaCl

the ionic charge for each element is shown on the periodic table ionic charges follow a predictable patterns in family groups

Characteristics of Ionic Compounds made of metal & non metal bonds formed by transfer of electrons metal ion is positive… non-metal ion is negative bonds are very strong bond until in water and then become very weak (compound dissolves) solid at room temperature good conductors of electricity (in solution) ionic compounds used for batteries!

Naming Ionic Compounds metal is first… then non metal just say the metal’s name eg. Na is sodium take the non metal’s name and change last 3 (or 4) letters to “ide” e.g. Cl is chlorine… changed to chloride … so NaCl is called sodium chloride

Some More Examples CaO: calcium and oxygen → calcium oxide Mg3N2: magnesium and nitrogen → magnesium nitride Al2O3: aluminum and oxygen → aluminum oxide KI: potassium and iodine → potassium iodide BaF2: barium and fluorine → barium fluoride

What is the Chemical Formula? look at the name of the 1st element (metal)… and write down its symbol e.g. sodium chloride – the 1st element is sodium or Na look at the name of the 2nd element (non metal) → you should be able to tell what it is even with the “ide” ending… and write down its symbol e.g. sodium chloride – the 2nd element is chlorine or Cl then you need to balance the charges to “0”

Balancing Charges the “net” charge of a compound must be zero e.g. Na+ + Cl- → NaCl +1 + –1 → 0 the number of atoms of an element must be correct to create a balanced charge e.g. Ca+2 + 2Cl- → CaCl2 +2 + 2(–1) → 0

the chemical formula will show how many atoms of each element are present in the compound e.g. NaCl has 1 atom of Na and 1 atom of Cl e.g. CaCl2 has 1 atom of Ca and 2 atoms of Cl NaCl CaCl2

More than One Ion Charge? some elements like Fe, Cu and Pb can form more than one ion charge to show which ion is present in a compound a Roman numeral is added to the compound name e.g. FeO is called iron (II) oxide because Fe+2 is present: Fe+2 + O-2 → FeO and Fe2O3 is called iron (III) oxide because Fe+3 is present: Fe+3 + O-2 → Fe2O3

Some More Examples Ca+2 + O-2 → CaO calcium oxide Mg+2 + N-3 → Mg3N2 magnesium nitride Al+3 + O-2 → Al2O3 aluminum oxide K+ + I- → KI potassium iodide Ba+2 + F- → BaF2 barium fluoride Fe+3 + Cl-2 → Fe2Cl3 iron (III) chloride Ti+4 + O-2 → Ti2O4 titanium (IV) oxide

Polyatomic Ions groups of non-metalic atoms which combine and act as one they have a charge… + or – they often involve oxygen polyatomic… poly meaning “many” atoms some common polyatomic ions are: e.g. NO2- nitrite e.g. NO3- nitrate e.g. SO3-2 sulfite e.g. SO4-2 sulfate e.g. CO3-2 carbonate e.g. OH- hydroxide polyatomic (non-metalic) ions can combine with metalic ions to form ionic compounds e.g. Ca+2 + CO3-2 → CaCO3 calcium carbonate

Naming Polyatomic Ionic Compounds notice that compounds with polyatomic ions normally end with “ite” or “ate” … different from the “ide” ending used for regular ions e.g. Cu+2 + NO3-2 → CuNO3 copper (II) nitrate e.g. H+ + SO4-2 → H2SO4 hydrogen sulfate (also called sulfuric acid)

Molecular Compounds molecule diatomic molecules is a cluster of atoms joined together is the smallest independent unit of a pure substance bond is strong diatomic molecules molecules made of 2 atoms of the same element… bond is strong e.g. O2, N2, H2

binary molecular compounds made of two different elements e.g. carbon dioxide CO2 molecular compounds may be made of more than 2 elements… and in fact can become quite complex e.g. glucose C6H12O6 each compound consists of specific proportions of each element

molecular compounds form from NON-METALS bonds are created by the SHARING of an electron between elements e.g. CO2 H O H2O H

Characteristics of Molecular Compounds made of two or more non metals bonds formed by sharing of electrons bonds are strong but attraction is weak (will break apart when changing state) solid, liquid or gas at room temperature poor conductors of electricity (no metals/ions)

Naming Molecular Compounds Prefix + 1st Element Name AND THEN Prefix + 2nd Element Name (ending changed to “ide”) e.g. carbon dioxide CO2 the prefix in the written name matches the number of atoms of that element indicated in the formula

a prefix written before the name of the element it refers to Prefixes tell us how many atoms of the element are present in the compound 1 = mono* 3 = tri 5 = penta 2 = di 4 = tetra 6 = hexa (* mono is used with 2nd elements, and implied if no prefix is present with 1st elements) a prefix written before the name of the element it refers to e.g. N2O - dinitrogen monoxide N2O3 - dinitrogen trioxide PF5 - phosphorus pentafluoride CO - carbon monoxide CCl4 - carbon tetrachloride

the chemical formula will show how many atoms of each element are present in the compound e.g. NH3 has 1 atom of N and 3 atoms of H when drawing a representation of the compound make the element with the larger atomic mass larger H H N H

Some Molecular Compounds Also Have Common Names especially those with H

Properties of Molecular and Ionic Compounds