Chemistry Unit Molecules and Compounds

Chemistry UnitMolecules and Compounds

Chemical Formula • Indicates: • _____________________________ • The _______________________________________ of each element Ex: H2O • The symbols H and O indicate the presence of hydrogen and oxygen, while the number 2 indicates that there are 2 atoms of hydrogen per one atom of oxygen Note: You do not need to write the number “1” if there is only one molecule of an element. If there is no number beside the element, it is assumed there is only one molecule of that element.

How do Atoms Bond? • There are two basic types of bonding: • ___________ Bonding • ____________ Bonding

Ionic Bonding • Attraction between _____________________ _____________________________________ • Usually between a ______________________ • Atoms of metals tend to lose one or more electrons (____________), whereas atoms of non metals tend to gain one or more electrons (___________)

Ionic Bonding • Ex: Na+ and Cl- are attracted to each other because they are oppositely charged ions; these two ions give us NaCl (table salt)

Ionic Bonding Continued • The chemical formula for an ionically bonded molecule is called a _____________________, which is the smallest electrically neutral collection of ions • Ex: NaCl, MgCl2, Li2O, H3PO4 all represent formula units

How do we know the Charges of Ions? • Remember how elements will lose or gain an electron to become more stable….group 1 elements lose one electron to give them a charge of +1, group 6 gains two electrons to have a charge of -2.

Ionic Bonding continued • ______________________: a single ionized atom Ex: Na+, Cl-, Mg2+, Fe2+, Fe3+ • ______________________: made up of two or more atoms joined by covalent bonds Ex: NO3-, NH4+ * Notice how some transition metals can have more than one charge *

Oxidation States • Oxidation state is the ____________________ _____________________________________ when joining with other atoms in compounds (same as charge of ion) • When added together, the formula unit of a compound should be 0! • Ex: NaClNa+ is in an oxidation state of +1 and Cl- is in an oxidation state of -1. 1 + (-1) = 0

Naming Compounds • Compounds formed by _________________ or carbon and hydrogen together with oxygen, nitrogen and a few other elements are organic compounds • All other compounds that do not fit this description are inorganic compounds

Name and Formulas of Inorganic Compounds: Binary Compounds • ________________ compounds: those formed between two elements • To name a binary compound that consists of a ____________________________: • Write the unmodified name of the metal • Then write the name of the nonmetal, modified to end in “ide”

Name and Formulas of Inorganic Compounds: Binary Compounds • ExamplesNaCl = _________________________ • MgI2 = ____________________________Al2O3 = ______________________________ • Ionic Compounds must be electrically neutral (total charge of the ions in a formula unit must be zero)

Binary compounds: Metal/Nonmetal • Transition metals form several ions, for example, iron forms two common ions, Fe2+ and Fe3+ • Use roman numerals to indicate which one was used (Fe2+ = Iron(II) and Fe3+ = Iron (III) )

Binary compounds: Metal/Nonmetal • Ex: Fe2S3 = __________________________ • Note: we looked at the number of S atoms to get Iron(III) • Fe2S3 is electrically neutral 2(3) + 3(-2) = 0

Binary compounds: Metal/Nonmetal • Old system used the words ferrous/ferric instead of Fe2+ and Fe3+ • Another example: Cu2O is Copper(I) Oxide or Cuprous oxide, CuO2 is Copper (II) Oxide or Cupric Oxide.

Binary compounds: Polyatomic Ions • First name of the element and the name of the polyatomic ion • Do not need to change the name to end in “_______”, just keep the name as is. • Ex: NaNO3 is _______________________ NOT Sodium Nitride

Binary Compounds: Two Nonmetals • Write the element with the positive oxidation state first: HCl not ClH • Second element still ends in “ide” but need to use prefixes: Mono = 1 Tetra = 4 Di = 2 Penta = 5 Tri = 3 Hexa = 6 • Examples: SO2 = ___________________B2Br4 = ________________________ * Need to know these prefixes *

Binary Compounds: Two Nonmetals • More examples: NO = __________________________________ (Note that it isn’t mononitrogen monoxide, mono is never used in the first named element) H2O = ___________________________ (water)

Inorganic Compounds: Hydrates • Each formula unit of the compound has associated with it a _____________________ of water molecules • To name: write down compound name according to nomenclature rules and then add ________________. • Example: CoCl2●6H2O___________________________

Summary of Naming

Covalent Bonding • Is the ___________________ • It occurs between a: • ________________________ • semimetal and nonmetal • semimetal and semimetal • We already learned how to name covalent compounds!(By ______________________ and ending the last element in “_____”.)

How do Covalent Bonds Form? • Atoms _____________________ with other atoms in order to complete their shell. • _____________: Atoms can have a maximum of ____ valence electrons in their outer shell. • ___________ – The attraction between atoms • _______________ - a pair of electrons that are left on their own around a central atom. • _____________________ – the one that has the most atoms attached to it (usually the one with the lowest electronegativity; exception is hydrogen, it is never the central atom).

Ionic vs. Covalent Bonding • Ionic: _______________ of electron(s) from one atom to another. Example is Sodium Chloride, NaCl Covalent: The atoms _____________ electrons. Example is Methane, CH4 C H Na Cl Cl H C H H H H H H - + H H C Na H H

Practice! • Lewis Structures for Molecules worksheet

So what is a Compound? • Compounds are ________________________ and not mixtures (Examples: Water (H2O), Carbon Dioxide (CO2) ) • Compounds are made of atoms of two or more elements

Chemistry Unit Molecules and Compounds