Chemistry Theory P2

binary compounds

binary compounds

a two-element compound

binary ionic compounds

contain a positive ion (cation) always written first in the formula and a negative ion (anion).

oxyanions

series of anions contain an atom of a given element and different numbers of oxygen atoms.

binary covalent compounds

are formed between two nonmetals.

acid

a substance that produces hydrogen ions in solution; a proton donor.

Atoms combine to form molecules by sharing electrons to form covalent bonds.

• Molecules are described by chemical formulas.

• Chemical formulas show number and type of atoms.

  -Structural formula

  -Ball-and-stick model

  -Space-filling model

formation of ions

• Cation—formed by loss of an electron, positive charge

• Anion—formed by gain of an electron, negative charge

• Ionic bonds—formed by interaction of cations and anions

The periodic table organizes elements in order of increasing atomic number.

• Elements with similar properties are in columns, or groups.

• Metals are in the majority and tend to form cations.

• Nonmetals tend to form anions.

Compounds are named using a system of rules depending on the type of compound.

• Binary compounds

  -Type I—contain a metal that always forms the same cation

  -Type II—contain a metal that can form more than one cation

  -Type III—contain two nonmetals

• Compounds containing a polyatomic ion

chemical stoichiometry

the calculation of the quantities of material consumed and produced in chemical reactions.

mass spectrometer

an instrument used to determine the relative masses of atoms by the deflection of their ions on a magnetic field.

average atomic mass

the atomic mass for that element.

mole

the number equal to the number of carbon atoms in exactly 12 grams of pure 12C: Avogadro’s number. One mole represents 6.022 x 10^23 units.

Avogadro’s number

the number of atoms in exactly 12 grams of pure 12C, equal to 6.022 x 10^23.

molar mass

the mass in grams of one mole of molecules or formula units of a substance; also called molecular weight.

mass percent

the percent by mass of a given element in a compound.

empirical formula

the simplest whole number ratio of atoms in a compound.

molecular formula

the exact formula of a molecule, giving the types of atoms and the number of each type.

chemical equation

a representation of a chemical reaction showing the relative numbers of reactant and product molecules.

reactants

a starting substance in a chemical reaction. It appears to the left of the arrow in a chemical equation.

products

a substance resulting from a chemical reaction. It is shown to the right of the arrow in a chemical equation.

balancing a chemical equation

there must be the same number of each type of atom on the product side and on the reactant side of the arrow. Making sure that this rule is obeyed is called balancing a chemical equation for a reaction.

mole ratio

the ratio of moles of one substance to moles of another substance in a balanced chemical equation.

Stoichiometry

• Deals with the amounts of substances consumed and/or produced in a chemical reaction.

• We count atoms by measuring the mass of the sample.

• To relate mass and the number of atoms, the average atomic mass is required.

mole

• The amount of carbon atoms in exactly 12 g of pure 12C

• 6.022 x 10^23 units of a substance

• The mass of one mole of an element = the atomic mass in grams

molar mass

• Mass (g) of one mole of a compound or element

• Obtained for a compound by finding the sum of the average masses of its constituent atoms

Percent composition

• The mass percent of each element in a compound

• Mass percent = mass of element in 1 mole of substance/ mass of 1 mole of substance x 100%

Empirical formula

• The simplest whole-number ratio of the various types of atoms in a compound

• Can be obtained from the mass percent of elements in a compound

Molecular formula

• For molecular substances:

  • The formula of the constituent molecules

  • Always an integer multiple of the empirical formula

• For ionic substances:

  • The same as the empirical formula

Chemical reactions

• Reactants are turned into products.

• Atoms are neither created nor destroyed.

• All of the atoms present in the reactants must also be present in the products.

Characteristics of a chemical equation

• Represents a chemical reaction

• Reactants on the left side of the arrow, products on the right side

• When balanced, gives the relative numbers of reactant and product molecules or ions

Stoichiometry calculations

• Amounts of reactants consumed and products formed can be determined from the balanced chemical equation.

• The limiting reactant is the one consumed first, thus limiting the amount of product that can form.