Honors Chemistry - Final Study Guide

basically everything

Subatomic Particles

Particles that when joined together form an atom; they are the proton (which holds a positive charge), the electron (which holds a negative charge), and the neutron (which holds a neutral charge).

Isotope

Form of any given element containing a specific number of neutrons in the nucleus of the atom; represented by its element and mass number.

Atom

Particle that makes up all of matter and is comprised of subatomic particles. Various elements, ions and isotopes can be made depending on how many subatomic particles are found in the particle.

Molecule

Two or more atoms chemically bonded together and share valence electrons and have a specific geometric shape as defined by Lewis Structures. Another word is compound.

Element

Pure substance comprised of a single atom with a specific number of protons. All of these are listed on the periodic table. This cannot be decomposed into smaller parts.

Compound

Pure substance comprised of more than one atom in fixed proportions. They can be decomposed into their elements and are more common in the natural world. Another word is molecule.

Mixture

Substance made of two or more different elements or compounds combined in variable proportions; can be divided into homogeneous and heterogeneous.

Pure Substance

Substance made of just one element or compound.

Ion

Form of any given element containing a specific number of electrons that are gained/lost in a chemical reaction. Some of these may be positive or negative because element naturally strive to have the same number of electrons as the balanced and stable noble gasses. Positive variants are called cations (which can usually be found on the left side of the periodic table), and negative variants are called anions (which can usually be found on the right side of the periodic table).

Predicting Ionic Charges

You can predict what the ionic charge of a main group element will be based on its group. The charges are as follows: 1A is +1, 2A is +2, 3A is +3, 5A is -3, 6A is -2, 7A is -1, and 8A is 0. There are a few elements which also have a predictable ionic charge, such as Ag with a charge of +1, and Zn & Cd with a charge of +2. You cannot predict the charges of transition metals.

Metal

Element that tends to lose electrons during chemical reactions (positive ionic charge) and is a solid at room temperature. Metallic character leans toward the bottom left side of the periodic table, where the metals are located.

Non-metal

Element that tends to gain electrons during chemical reactions (negative ionic charge) and is a gas at room temperature. Nonmetallic character leans toward the upper right side of the periodic table, where the nonmetals and metalloids are located.

Chemical Change

Change made to a substance that altars the chemical composition of that substance during a chemical reaction. The indicator of this is when a new substance is formed due to the reaction.

Physical Change

Change made to a substance that altars the appearance of the substance, without actually changing the chemical composition of the substance. You can detect this with your five senses after a reaction, but you won’t see any new substances formed.

Chemical Reaction

Reaction between two elements/molecules which altars the chemical composition of the reactants, creating a new substance as a product. There are many types of these, including Synthesis, Decomposition, and Single/Double Replacement.

Precipitation Reaction

Double Replacement reaction where the anions switch which cation they are bonded to. Two new compounds will be formed. An example could be NaCl + AgNO₃ → NaNO₃ + AgCl. To write these, first write the products by swapping the anions, then in any order, balance the compounds and equation, write the charges of all ions involved, and determine the solubility of the compounds which are products (the reactants will always be aqueous) in parenthesis after the compound. Last, write any net ionic equations necessary if a reaction has occurred (there is no reaction if there is no solid).

Water Solubility of Ions

The water solubility of certain ions can be predicted. For example, Li⁺, Na⁺, K⁺, NH₄⁺, NO₃⁻, and C₂H₃O₂⁻ are always soluble while Pb²⁺, CO₃²⁻, and PO₄³⁻ are never soluble unless paired with an always soluble ion. A soluble ion or compound is labeled as aqueous, while an insoluble ion or compound will be labeled as a solid (this is the usual state of matter), liquid or gas.

Redox Reaction

Chemical reaction where electrons transfer during the reaction. This can be when elements become compounds or when elements are ionized and vice versa. Under this category there are Synthesis reactions, where two elements combine to make a new compound (A + B → AB), Decomposition reactions, where a compound separates into two elements (AB → A + B), and Single Replacement reactions, where an element/ion takes the place of an element/ion in a compound, leaving the other element/ion separate as a second product (AB + C → AB).

Double Replacement Reaction

Non-redox reaction where all the atoms/molecules are already ionized. The reactants are two compounds, and the products are two different compounds with swapped ions. Three types of these are Precipitation reactions, Acid-Base reactions, and Gas Evolution reactions.

Acid-Base Reaction

Double Replacement reaction where an acid (the generic acid is H⁺) and a base (the generic base is OH⁻) are mixed, creating water and another new compound composed of the two ions paired with the H⁺ and OH⁻. The equation for this reaction would be HA + BOH → H₂O + BA, where BA is almost always aqueous. Unless this is not the case for BA, the generic net ionic equation would be H⁺(aq) + OH⁻(aq) → H₂O(l).

Net Ionic Equation

Equation written based on the outcome of a Double Replacement Reaction showing how an insoluble product of the reaction was formed. This shows the actual reaction that took place. They are written by showing how the ions when combined make the insoluble compound. Be sure to balance these and include charges and states of matter as well (similar to precipitation reactions, all the reactants are aqueous).

Gas Evolution Reaction

Double Replacement reaction where the products are two compounds, with one of which decomposing into a gas and water, ultimately outputting three products. The following decomposition process is a redox reaction while the initial reaction is not. An example of this reaction could be NH₄A + BOH → NH₄OH + BA, with the resulting reaction being NH₄OH → NH₃(g) + H₂O(l). There will be a net ionic equation for the gas and the water, and if BA is a solid then there will be one for that as well.

Molar Mass

The ratio of grams of a substance to moles of that same substance. Can be calculated by dividing the amount of grams you have by the amount of moles you have of the given substance, or when told the chemical you can take their molar masses on the periodic table and add them (if an element is repeated, multiply that element’s molar mass by however many atoms of that element your chemical contains). It is used as the conversion factor relating mole count and gram count as well; when given a number of grams, divide by the molar mass to find mole count, and when given a number of moles, multiply by the molar mass to find gram count. The unit for this is g/mol.

Stoichiometry

The ratio that relates the moles of one chemical to the moles of another when given an equation. For any given chemicals, this ratio would be the moles of the chemical we want needed in the reaction (multiplied by how much we are given of said chemical) divided by the moles of the chemical we have needed in the reaction. After multiplying this conversion factor by the amount of the chemical given, the quotient will be the moles of the chemical we want that we will be able to make/use in the reaction. Sometimes a conversion from grams or another unit is required first before and/or after performing the stoichiometric conversion. When converting to energy, put the value of ∆H in the numerator of the conversion and the moles of the chemical needed in the reaction in the denominator of the conversion, then multiply.

Mole Conversions

When dealing with grams, the conversion factor is the molar mass. When given grams, divide by molar mass for moles and when given moles, multiply by molar mass for grams. When dealing with atoms/molecules, also labeled as formula units, the conversion factor is avogadro’s number (6.022 × 10²³). When given formula units, divide be avogadro’s number for moles and when given moles, multiply by avogadro’s number for formula units. When needed to convert from grams to formula units or vice versa, a decent rule of thumb is to divide by the conversion factor relating to what you have first, then multiply by the conversion factor relating to what you need.

Orbitals

Region of an atoms where there is a maximum probability you will find the electron in question residing in at any given time. There are four kinds: s orbitals (spherical regions which can hold 2 electrons and are at the same energy level as the row the element is located in on the periodic table), p orbitals (can hold 6 electrons and are at the same energy level as the row the element is located in on the periodic table), d orbitals (can hold 10 electrons and are one energy level behind the row the element is located in on the periodic table), and f orbitals (can hold 14 electrons and are two energy levels behind the row the element is located in on the periodic table). Configurations of electrons in their proper orbitals can be written out, abbreviated, or drawn in diagrams.

Limiting Reactant

When dealing with stoichiometry, sometimes it can be hard to determine which chemical in a reaction has an excess. When this is the case, you must find this value by finding the moles of the chemicals you are given. From here, you can either decide which element we would run out of first if we kept the reaction going until we ran out and complete the stoichiometry problem with that element or do the problem for both elements and take the element will a smaller answer. Whichever element you run out of first is called the limiting reactant; the other is called the excess reactant. The answer to the stoichiometry problem is the one that is obtained by using the limiting reactant.

Percent Yield

When you have an answer to a stoichiometry problem, you can use the answer you got from the problem to determine how much of the reaction was completed based on how many grams of the product of the reaction you have once it is complete. When given this number, divide it by your answer to your stoichiometry conversion and multiply it by 100% to get your percent yield.

Excess Reactant

This is the reactant in a reaction that you have an abundance of and will not run out of, and therefore you don’t need to worry about it when solving stoichiometry problems (once you’ve actually determined the limiting reactant). Sometimes you will be asked to find how much of an excess reactant you’ve used. To do this, take how much you started with and subtract it by the answer you get after doing the stoichiometry from converting from the limiting reactant to the excess reactant.

Valence Electron

Electron residing in an orbital at the energy level furthest away from the nucleus which can be shared with other atoms when paired in a chemical bond. When given an electron configuration, valence electrons can be counted by looking at how many electrons there are at the highest energy level. When drawing the structures of compounds according to Lewis Structures, these are drawn as small dots (in pairs) around the element on any applicable sides that do not have a chemical bond already. These pairs are called “lone pairs.” Each element has a different amount of valence electrons: for example, hydrogen has 1, beryllium has 2, boron has 3, carbon has 4, nitrogen has 5, oxygen has 6, fluorine has 7 and neon has 8.

Atomic Radius

This is the distance between the nucleus of the atom and the outermost electrons in that atom. Across the periodic table, the atomic radius tends to decrease when going from left to right because there are more protons present in elements closer to the right, causing a greater electromagnetic pull (the factor which affects atomic radius the most) on the electrons and bringing them closer to the nucleus. However, when going from up to down on the periodic table, atomic radius increases as there are more energy levels with each row.

Ionization Energy

This is the amount of energy required to “ionize” an atom from its neutral state. This trend of energy increases when going from left to right on the periodic table and decreases when moving from up to down a column on the periodic table. This is because since noble gasses are stable when neutral, they will require lots more energy to adjust one of their electrons than an alkali for instance, which is unstable and therefore wouldn’t take much to lose an electron. The main factor here is the ionic form of the element in question.

Electromagnetic (Light) Spectrum

Light is a form of electromagnetic radiation that has various wavelengths, which create different waves on the electromagnetic spectrum. Those with the longest wavelengths and lowest frequencies are radio waves; next comes microwaves, then infrared rays, then the visible light spectrum (a small sliver containing red, orange, yellow, green, blue, indigo and violet), then ultraviolet rays, x-rays, and finally gamma rays. Radio waves have the least amount of energy while gamma rays have the most energy.

Wavelength

The distance between two adjacent wave crests in a wave, or the distance across one whole wave, represented by λ. Has an inverse relation with a wave’s frequency.

Frequency

The amount of wavelength cycles that pass through any given point in one second, represented by v. Has an inverse relation with a wave’s wavelength.

Ionic Compound

Molecule made of a metal, which has a positive ion, and a nonmetal, which has a negative ion, or a polyatomic ion (if it’s positive it takes the place of the metal, if it’s negative it takes the place of the nonmetal), which contains ions as the name implies. To name these, first list the positive ion, and if necessary add the charge of this ion in parenthesis after you list it has a roman numeral, then the negative ion with the suffix -ide in place of the second vowel. However, do not add the suffix -ide if the negative ion is a polyatomic ion; if this is the case leave it as is. To write the compound, write the symbol for the positive ion and then the symbol for the negative ion. Then determine the subscripts of each element (a good shortcut is to swap their charges and place those numbers as the subscripts, but this is fallible) and then simplify if necessary.

Binary Covalent Compound

Molecule made of two different nonmetals and does not contain ions. To name these, first list the first nonmetal with the appropriate prefix for however many atoms are required (1 - mono, which we don’t write in the first element, 2 - di, 3 - tri, 4 - tetra, 5 - penta, 6 - hexa, 7 - hepta, 8 - octa, 9 - nona, and 10 - deca). Next, write the second nonmetal with the appropriate prefix and include the suffix -ide in place of the second vowel. If oxygen is one of the nonmetals in the compound, drop the a or o in the suffix you’re using and instead use oxygen’s o.

Balancing Reactions

During a reaction, the products must have the same amount of material as the reactants, due to the law of Conservation of Mass. Therefore, we must make sure there is an equal amount of each element on both sides of the reaction by balancing the reaction. To do this, you must ensure that all the subscripts and coefficients of every chemical adds to up give you the same amount of each element on both sides of the equation. Polyatomic ions do behave as one element while balancing equations. A general assumption that can be made is that the largest compound has a coefficient of 1, but this isn’t always the case and is instead more of a starting base to go off of when balancing your reaction.

Spectator Ion

Ion that is present in a reaction but doesn’t actually participate in it and is aqueous as a reactant and product of the reaction. Since all reactants in precipitation reactions are aqueous, you can safely say that any product which is aqueous ion is a spectator ion. These will not be included in any net-ionic equations.

Combustion Reaction

Redox reaction where something reacts with the gas O₂, making this reaction either synthesis or single replacement.

Electronegativity and Electron Affinity

These two periodic trends are very similar and have the same pattern across the periodic table. First, electronegativity is the ability of an atom to attract an outside electron to it. Meanwhile, electron affinity is the amount of energy released when a neutral atom gains the electron it attracted. For both trends, electronegativity and electron affinity increase when going from left to right across the periodic table and decrease as you go from up to down in a column.

Lewis Structures

Way of visually showing a compound and the chemical bonds within it. They show how valence electrons are shared between atoms so that all the atoms can have four pairs of valence electrons and be stable like the noble gasses. Each element can only have a certain number of bonds, as it is so to create enough pairs; for example, hydrogen only needs one bond, beryllium needs 2, boron needs 3, carbon needs 4, nitrogen needs 3, oxygen needs 2, fluorine needs 1 and neon doesn’t need any, as it already has four even pairs of electrons. In order to draw a compound with this structure formation, first you must decide on a central atom. For this you can use your own judgement, but be warned that there won’t always be a central atom. After, connect all your atoms somehow to the central atom with a single bond first. In the event there is no central atom, just connect the elements you have together. Then, if necessary, from here you can either visually see where you can use some double or triple bonds, or it might be helpful to count how many valence electrons you need to account for and based off that decide where any double or triple bonds should go. After you do all this, draw in your lone pairs as dots around each element if the element has any. If you’re drawing a polyatomic ion, you can either put brackets around your ion and write the charge or just write the charge with the central atom.