Chemistry 2 CPE - FINAL EXAM STUDY GUIDE - DeMartini

Atoms

Consists of energy levels, sublevels, and orbitals where electrons are found.

Electron configuration

The arrangement of electrons in an atom's energy levels and sublevels.

s

2

p

6

d

10

f

14

Orbital configuration

Shows electrons as arrows in boxes representing orbitals within sublevels.

Valence electrons

Electrons in the outermost energy level involved in bonding.

History of the periodic table

Created by Dimitri Mendeleev, who organized elements by increasing atomic mass and similar properties.

Periods 1-7

Horizontal rows on the periodic table, which indicate energy levels of electrons.

S~block

Left side

P~Block

Right side

D~block

Middle transition metals

F~block

Bottom inner transition metals

Group 1 – Alkali Metals

1 valence electron

VERY REACTIVE

Not typically found in nature as free elements because they are so reactive.

Combine with non-metals and react strongly with water to produce hydrogen gas and aqueous solutions

Group 2 – Alkaline Earth Metals

2 valence electrons

Harder, denser, and stronger than alkali metals.

Higher melting points

Too reactive to be found in nature as free elements.

Transition Elements.Gr 3-12 “d block”

Some element electron configurations are not consistent with the orderly d sublevel filling order

Metals with metallic properties

relatively unreactive

Noble Gases

Group 18

helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn), and oganesson (Og).

Atomic radius

Size of an atom, Decreases across a period and Increases down a group.

Halogens

Consists of elements in group 17 on the Periodic Table (F, Cl, Br, I, At)

Highly reactive nonmetals

7 valence electrons

Ionic radii

The size of an ion: cations are smaller, and anions are bigger.

Cations

Positively charged ions

Anions

Negatively charged ions

Protons

Positively charged particles

Electrons

Negatively charged particles

Neutrons

Neutral charge

Ionization energy

Energy required to remove an electron from an atom, increases across a period, decreases down a group.

Ionization energy generally increases across a period (left to right) due to increasing nuclear charge, while it decreases down a group (top to bottom) due to increasing atomic radius and electron shielding

Electron affinity

Energy change when an atom gains an electron, generally becomes more negative across a period.

When an atom gains an electron, it becomes a....

Negatively charged ion called an anion. This is because the atom now has more electrons than protons, resulting in a negative charge.

Electronegativity

Ability of an atom to attract electrons in a bond, increases across a period, decreases down a group.

Electronegativity decreases as you move down a group in the periodic table because the atomic radius increases, making the nucleus less effective in attracting electrons. Conversely, electronegativity increases as you move across a period because the atomic radius decreases due to increasing nuclear charge.

Significance of a chemical formula

Shows the types and numbers of atoms in a compound.

Monatomic ions

Consist of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons

Binary ionic compounds

Involve combining the compound's (+) and (-) ions.

Cation is named first, and Anion follows (~ide) ending.

Stock system of naming compounds

Uses Roman numerals to show metal ion charge.

Type 2 Binary Ionic Compounds

These form between ONE metal from the d~block (groups 3-12) that forms more than one ion. You must use the stock system to name these compounds.

Naming compounds using prefixes

Used for covalent compounds to indicate the number of atoms. BOTH ELEMENTS MUST BE ABOVE THE STAIRCASE.

Naming ternary compounds

Compounds with three or more elements, often containing polyatomic ions.

Covalent vs. ionic bonding

Covalent bonds share electrons; ionic bonds transfer electrons.

Percent composition

Percentage by mass of each element in a compound.

How to find percent compositon

1) Find the molar mass of each element in the compound

2)Add up both molar masses of each element in the compound

3)Divide the mass of each element (calculated in step 1) by the molar mass of the compound (calculated in step 2).

Multiply the result by 100% to express it as a percentage.

Example:

Let's calculate the percent composition of carbon dioxide (CO2):

Carbon: Molar mass of C = 12.01 g/mol. In CO2, there is 1 carbon atom, so the mass of C in CO2 is 12.01 g/mol.

Oxygen: Molar mass of O = 16.00 g/mol. In CO2, there are 2 oxygen atoms, so the total mass of O in CO2 is 2 * 16.00 = 32.00 g/mol.

Molar mass of CO2: 12.01 + 32.00 = 44.01 g/mol.

Now, calculate the percent composition:

% Carbon: (12.01 g/mol / 44.01 g/mol) * 100% = 27.29%.

% Oxygen: (32.00 g/mol / 44.01 g/mol) * 100% = 72.71%.

You can verify that the percentages add up to 100%.

Empirical vs. Molecular formulas

Empirical is the simplest ratio; molecular is the actual number of atoms.

How to find empirical formula

Percent to mass, mass to moles, divide by small, multiply until whole.

How to find molecular formula

Find molar mass, divide by the given mass, and multiply by the empirical.

Indications of a chemical reaction

Formation of precipitates, gas, color change, temperature change.

(s)

solid

(l)

liquid

(g)

gas

(aq)

aqueous,

→

yields

Δ

heat added, catalysts indicated.

Coefficients and subscripts

Coefficients show the number of molecules(big number); subscripts show a number of atoms in a molecule.(small number)

Word equations vs. formula equations

Word equations use names, formula equations use chemical symbols and formulas.

Balancing equations

Adjust coefficients to have equal atoms on both sides.

Types of chemical reactions

Synthesis (combine), decomposition (break apart), single replacement, double replacement, combustion (react with O₂).

Mg + O2 → MgO2

Synthesis

2Al2O3 → 4Al + 3O2

Decomposition

Zn + 2HCl → ZnCl2 + H2

Single Displacement

2NaOH + CuSO4 → Na2SO4 + Cu(OH)2

Double Displacement

CH4 + 2O2 → CO2 + H2O

Combustion

Types of stoichiometry problems

Convert mole~to~mole, mole~to~mass, mass~to~mole, and mass~to~mass.

Percent yield

Actual yield divided by theoretical yield times 100%.

Limiting reactants

The reactant that runs out first, limiting the amount of product formed.