B4W11CompoundsNotes

Notes: Week 11 - Compounds

Topics covered:

• Elements vs compounds
• Chemical formulas
• Ionic vs Covalent compounds
• Naming compounds

Vocab:

• Compound, Chemical Bond, Chemical Formula, Ionic Bond, Covalent Bond

Compounds

= two or more elements that are chemically bonded together - Are pure substances (cannot be physically separated) Chemical bond = attractive force that holds atoms together - Strong but flexible - Formed by atoms losing, gaining or sharing electrons

Compounds

• Written using a Chemical Formula

= uses the element abbreviation and subscripts that shows the atoms in a compound

• Example: Table Sugar

C12H22O11

Compound or Element?

CO Co NAt

Compound or Element?

Elements must have a capital letter! If see lower case letter, part of capital letter CO - 1 compound (2 capital letters) Co - 1 element NAt - 1 compound

Chemical Formula - Aspirin

C9H8O4

What elements are present? How many atoms of each element? How many total atoms?

Chemical Formula - Aspirin

C9H8O4

What elements are present? Carbon, Hydrogen, Oxygen How many atoms of each element? C - 9, H - 8, O -4 How many total atoms? 9+8+4 = 21

Chemical Formula - Indigo

C16H10N2O2

What elements are present? How many atoms of each element? How many total atoms?

Chemical Formula - Indigo

C16H10N2O2

What elements are present? Carbon, Hydrogen, Nitrogen, Oxygen How many atoms of each element? C - 16, H - 10, N - 2, O -2 How many total atoms? 16+10+2+2 = 30

Chemical Formula – Magnesium Hydroxide

Mg(OH)2

What elements are present? How many atoms of each element? How many total atoms?

Chemical Formula – Magnesium Hydroxide

Mg(OH)2

What elements are present? Magnesium, Oxygen, Hydrogen How many atoms of each element? Mg - 1, O - 2, H -2 How many total atoms? 5

Chemical Formula – Hydrogen Peroxide

3 H2O2

Coefficient indicates how many compounds there are

What elements are present? How many atoms of each element? How many total atoms?

Chemical Formula – Hydrogen Peroxide

3 H2O2

Coefficient indicates how many compounds there are

What elements are present? H, O How many atoms of each element? H = 6 O = 6 How many total atoms? 12

What holds bonded atoms together?

• The outermost orbital of a bonded atom is full of electrons

1. Atoms bond when their valence electrons interact 2. Atoms will join so that each atom has a full/stable valence shell - Octet rule → balanced & stable - NET CHARGE OF ZERO!!!

Ionic Bonds

= formed by the attraction between oppositely charged ions (metal + non metal) Cations = have a positive charge

• protons > electrons
• Groups 1-14 (metals)
• always written first!

Anions = have a negative charge

• electrons > protons
• Groups 14-18 (nonmetals)

Ionic Bonds

• formed by the transfer of electrons

1. One atom loses and the other gains the electrons being transferred 2. This results in positive and negative ions that are attracted to each other 3. Each positive ion is attracted to negative ions, each negative ion is attracted to positive ions, creating a crystal lattice ( 3-D arrangement of alternating charges)

Ionic Bonds

• Properties of Ionic Compounds

- Hard - Brittle - High melting/boiling points - Solid at room temperature - Can conduct electricity when a liquid

Covalent Bonds

= bond formed when atoms share one or more pairs of electrons (nonmetal + nonmetal)

• Properties:

- any state of matter at room temperature - tend to have low melting points - molecules are free to move when dissolved or melted - do not conduct electricity

Covalent Bonds

• Atoms joined by covalent bonds share electrons

- Valence electrons can be shared in pairs between two atoms in order to fill the outer shell with 8 electrons

Covalent Bonds

• Single bond = one single line = 2 shared electrons

- Double bond = 2 lines between atoms = 4 Shared electrons - Triple bond = 3 lines between atoms = 6 shared electrons (strongest bond type, but also most unstable)

• most always involve

nitrogen

Lone Pairs

• Electrons not involved in

bonding are represented by dots *sometimes also called unshared pair

Covalent Bonds

Hydrogen will always form a single bond! Will never have ‘quadruple’ bond because compound would be too unstable (will learn more about in chemistry)

Question

Covalent or Ionic? Why? MgCl2 = CH4 = NO2 = KBr =

Question

MgCl2 = Ionic (metal + nonmetal) NO2 = Covalent (nonmetal + nonmetal) CH4 = Covalent (nonmetal + nonmetal) KBr = Ionic (metal + nonmetal)

Compound Names & Formulas

Recall… Ionic compound = nonmetal + metal Covalent compound = metal + metal

Naming Ionic Compounds

Remember: metal + nonmetal Have two names First name = name of cation Last name = name of the anion with the suffix (ending) changed chlorine chloride oxygen oxide nitrogen ? sulfur ? phosphorus ?

Naming Ionic Compounds

Remember: metal + nonmetal Have two names First name = name of cation Last name = name of the anion with the suffix (ending) changed chlorine chloride oxygen oxide nitrogen nitride sulfur sulfide phosphorus phosphide

Naming Covalent Compounds

• Tell the number of atoms of each element per molecule (you are expected to know these!)

1- Mono… 6- Hexa… 2- Di… 7- Hepta… 3- Tri… 8- Octa… 4- Tetra… 9- Nona… 5- Penta… 10- Deca…

• When a prefix ending in ‘o’ or ‘a’ is added to ‘oxide’, the final vowel in the prefix is dropped

Naming Covalent Compounds

First name = the numerical prefix plus the name of the first nonmetal - no prefix is given if it is ‘mono-’ Last name = numerical prefix plus the name of the second nonmetal with the ending changed to ‘-ide’ - prefix is always given - element farthest to the right on the periodic table is named last

Naming Covalent Compounds

Examples: N2O5 = _______________ CO = ________________ H207 = ______________ ____ = carbon tetrahydride ____ = phosphorous pentoxide ____ = disulfur trifluoride

Naming Covalent Compounds

Examples: N2O5 = dinitrogen pentoxide CO = carbon monoxide H207 = dihydrogen heptoxide CH4 = carbon tetrahydride PO5 = phosphorous pentoxide S2F3 = disulfur trifluoride

Drag the terms to their correct definition.

Chemical Bond

Covalent Bond

Ionic Bond

Compound

Chemical Formula

KEY

Chemical Formula

Covalent Bond

Compound

Ionic Bond

Chemical Bond