chemical bonding. electron configuration in ionic bonding valence electrons are electrons in the...
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Chemical Bonding
Electron Configuration in Ionic Bonding
• Valence Electrons are electrons in the highest occupied energy level of an atom
• These electrons determine the chemical properties of an element
Electron Configurations in Ionic Bonding
• Valence electrons can be determined by looking at the element’s electron configuration
• Ex: carbon is 1s22s22p2 or [He]2s22p2
• Valence e- = 2 + 2 = 4
Electron Configurations in Ionic Bonding
• Valence electrons are usually the only ones used in bonding
• These can be shown on electron dot structures
Electron Configurations in Ionic Bonding
• Octet Rule – in forming compounds, atoms tend to achieve the electron configuration of a noble gas
• All noble gases (except He) have eight valence electrons (s2p6)
Electron Configurations in Ionic Bonding
• Metals (elements on the left side of the periodic table) tend to form cations
• This is because it is easier to lose 1,2,3 or electrons than to gain 5,6,7
Electron Configurations in Ionic Bonding
• Nonmetals (elements on the right side of the periodic table) tend to form anions
• This is because it is easier to gain 1,2,3 electrons than to lose 5,6,7
Electron Configurations in Ionic Bonding
Group # Electron Config
Valence electrons
Ionic Charge
1 s1 1 +1
2 s2 2 +2
13 s2p1 3 +3
14 s2p2 4 NONE
15 s2p3 5 -3
16 s2p4 6 -2
17 s2p5 7 -1
18 s2p6 8 NONE
Formation of Ionic Bonds
• An ionic bond is the transfer of electrons, which results in two ions of opposite charge attracting to one another
• Ex: Na will give up one electron to Cl so that you have Na+ and Cl-, which are then attracted to one another forming NaCl
Naming Ions
• Cations: same element name, just add the word “ion” on the end– Ex: Na+ = sodium ion
• Anions: change the ending to “-ide” and add the word “ion” on the end– Ex: Cl- = chloride ion
Naming Ionic Compounds
• When naming an ionic compound, name the cation, then the anion (left to right)– Ex: NaCl = sodium chloride– K2O = potassium oxide
– The fact that there are numbers doesn’t affect anything (unless they are transition metals)
Naming Ionic Compounds
• To go from the name to the symbols, you need to know the ionic charges:– Ex: give the symbol for lithium nitride– Lithium is Li+ and nitride is N3-
– THE CHARGES MUST BALANCE!!– Therefore, there must be 3 lithiums for
every nitrogen = Li3N
Naming Ionic Compounds
• Transition metals usually form more than one cation
• When naming compounds containing transition metals, a roman numeral is used to indicate the charge
• Ex: CuCl = copper (I) chloride
• CuCl2 = copper (II) chloride
Naming Ionic Compounds
• Polyatomic Ions – an ion consisting of more than element; all of these elements work together as one “unit” and the entire “unit” has a specific charge
• These have special names that need to be memorized
• Naming is done in the same fashion
Naming Ionic Compounds
• Ex: CO32- is called carbonate
• What would the formula for calcium carbonate be? Lithium carbonate? Aluminum carbonate?– CaCO3
– Li2CO3
– Al2(CO3)3
CHARGES MUST STILL BE BALANCED
Covalent Bonding
• Covalent Bonding takes place between two non-metals and involves a sharing of electrons to obtain an octet
• Electrons that do not take place in the bond are called unshared pairs
Covalent Bonding
• Sometimes atoms will form multiple bonds to achieve stable configurations
• Double bonds involve 4 electrons being shared, and triple bonds involve 6 electrons being shared
Covalent Bonding
• Single bonds are the longest, followed by double, then triple
• Triple bonds are the strongest, followed by double, then single
Covalent Bonding
• Some elements are typically found in nature covalently bonded to another atom of the same element. These are called diatomic elements
• Ways to remember these 7:– BrINClHOF (brinkelhoff)– I Bring Clay For Our New House
Naming Molecules
• Covalent compounds are also known as molecules.
• Unlike ionic compounds, which would only form in one way, many different molecules can form from the same elements
Naming Molecules
• For example, what is the difference between CO and CO2?
• These are different compounds, but how would that be reflected in their name?
• Answer: by using numerical prefixes
Naming Molecules
• The prefixes are: Number Prefix
1 mono
2 di
3 tri
4 tetra
5 penta
6 hexa
7 hepta
8 octa
9 nona
10 deca
Naming Molecules
• CO has one C, one O => carbon monoxide
• CO2 has one C, two O => carbon dioxide
Naming Molecules
• Both elements in the compound need to have a prefix – unless the first one is mono, then it can be dropped
• Ex: P2O5 = diphosphorus pentaoxide
PO5 = phosphorus pentaoxide (no mono needed on the first element)
Naming Acids
• Acids are compounds that contain a hydrogen ion, and their name comes from the anion to which the hydrogen is bonded
• If it is bonded to a monatomic ion, the prefix hydro is added and the ending becomes “ic”: HCl is hydrochloric acid
Naming Acids
• If the anion is a polyatomic ion, no hydro prefix is added.
• If the ion ends in “ate” the ending changes to “ic”– Ex: HNO3 (anion is nitrate) = nitric acid
• If the ion ends in “ite” the ending changes to “ous” – Ex: HNO2 (anion is nitrite) = nitrous
acid
Naming Hydrates
• Hydrates are compounds that include water (H2O) in their structure
• Ex: CuSO4 ∙ 5H2O– Name the base portion first = copper
(II) sulfate– Name the hydrate portion second =
pentahydrate– Copper (II) sulfate pentahydrate
Metallic Bonding
• Bonds between metals atoms are called metallic bonds
• A metallic bond consists of the positive nuclei of the metal atoms in a “sea” of electrons
Properties of Ionic Compounds
• Ionic compounds tend to be:– Hard– Brittle– Have high boiling/melting points
Properties of Molecules
• Molecules can be either polar or nonpolar
• In a polar covalent bond, electrons are shared unequally
• In a nonpolar covalent bond, electrons are shared equally
Properties of Molecules
• Polarity of bonds can be determined using electronegativity differences (listed in a table)
• If the difference is 0-0.4, the bond is nonpolar covalent. If the difference is 0.5-2.0, the bond is polar covalent. If the difference is 2.1 or greater, the bond is ionic
Properties of Metals
• Metals are:– Shiny– Malleable (can be hammered into
shapes)– Ductile (can be drawn out into wires)
Properties of Metals
• Alloys are mixtures of metals that have properties of both metals– Ex: bronze, brass, sterling silver
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