Chemistry

Protons - a stable subatomic particle in the atomic nuclei w/ a positive charge equal in magnitude to that of an electron, but of opposite sign

Neutrons - A subatomic particle of about the same mass as a proton but w/out an electrical charge

Electrons - A negative charged subatomic particle that is 1/1836 times smaller than a proton

Electrons constantly move around the nucleus of an atom made up of protons and neutrons

The number of electrons and protons are equal

Atomic # = # of protons in an element

Atomic mass = home many protons and neutrons are in an element

How to find neutron # → neutrons = mass # - atomic #

Mass of 1 proton: 1.67×10²⁴ or 1 amu

Mass of 1 neutron: 1.67 × 10²⁴ or 1 amu

Mass of 1 electron: 9.109 × 10^-25 or .00059 amu

• Electrons are not considered in the mass # of an atom

Isotopes - Distinct nuclear species of the same chemical element. They have the same # and position in the periodic table, but differ in the # of neutrons

• Same element but w/ different weights

Ions - An atom or group of atoms w/ a net electrical charge.

• Atoms becomes an ion if it gains or loses electrons

  • Cation - positively charged atom → atom loses electron

  • Anion - negatively charged atom → atom gains an electron

“Cation are ‘paw’sitively charged”

Shell - electron revolve around the nucleus in a specific circular path known as orbit or shell

Subshell - A division of electron shells separated by electron orbital

Every shell has a subshell of s,p,d,f

Only electrons in the outermost shell participate in chemical bonds

| N=1   | K shell   | s  |
| N=2   | L shell   | s,p |
| N=3  | M shell   | s,p,d   |
| N=4   | N Shell   | s,p,d,f   |

Orbital - 3 dimensional space within an atom where an electron in a given subshell can be found

• S orbital

• P orbital

• D orbital

Shell #1:

• Subshell: S

• # of orbitals: 1

• Max # of electrons: 2

Shell #2:

• Subshell S,P

• # of orbitals: 1,3

• Max # of electrons: 8

Shell #3:

• Subshell S,P,D

• # of orbitals: 1,3,5

• Max # of electrons: 18

Shell #4:

• Subshell S,P,D,F

• # of orbitals: 1,3,5,7

• max # of electrons: 32

# of orbitals increase by +2. Electron # increase by 4 per subshell

EX: If magnesium has an atomic # of 12, it should be written out like:

• 1s²2s²2p⁶3s²

w/ the subscripts adding up to 12

Ionic bonds- Complete transfer of valence electron(s) between atoms

• Octet rule - Atoms prefer to have 8 electrons in their valence shell. They may lose, gain, or share electrons

• Ionic bonds have an “I take, you give” relationship

• EX: NaCl

Covalent bond - Sharing of electron pairs between atoms

• Typical between 4 major elements:

  • Carbon

  • Oxygen

  • Hydrogen

  • Nitrogen

  • “CHON”

Periodic Table

Row = Period

• Indicates how many electron shells an element has

Columns = Groups

• Indicates the # of valence electrons the element in the group has

• Doesn’t include transition metals (elements in the middle)

Physical Properties and Changes of Matter

Matter - Anything that has weight and occupies space/volume. Can be solid, liquid, or gas

Mass - The amount of matter an object contains

• Can be measured in grams (g) or kilograms (kg)

Volume - The amount of space an object occupies

• Can be measured in liters (L) or milliliters (mL)

Density - The relationship between the mass and volume of an object

• To calculate: Density = mass/volume

Solid:

• has definite shape

• Has definite volume

• Can’t compress

Liquid:

• Has indefinite shape (takes shape of container)

• has definite volume

• Can’t compress

Gases

• Has indefinite shape (takes shake of container)

• Indefinite volume (changes as it expands and contracts)

• Compressible

Temperature causes particles to increase its vibration

Increased pressure + lower temperatures can cause gasses to transition into liquid

Melting - When a solid gains heat and changes into a liquid

• EX: Ice → Water

Freezing - Process where a liquid loses heat and turns into solid

• Water → Ice

Condensation - Process where a gas loses heat and turns into a liquid

• Clouds created when water vapor in the air cools

Evaporation - Transformation of a liquid into a gas

Sublimation - Process where a solid changes directly into a gas w/out first becoming a liquid

Deposition - Also known as desublimation. When a gas changes directly into a solid w/out first becoming a liquid

• EX: Frost forming on a window

Chemical Reaction

Chemical Reactions - One or more substances, known as reactants, that are transformed into different substances called products

• Reactants - substances that present at the start of a chemical reaction that participates in the reaction

• Products - Substances that are formed as a result of a chemical reaction

Reactants are the ingredients to make the products

Combination - Two or more substances combine to form a single product

• EX: A + B → AB
  

Decomposition - A single substances breaks down into two or more substances

• EX: AB → A + B

Single Displacement - One element in a compound is replaced by another element

• EX: A + BC → B + AC

Double Displacement - Elements in two different compounds swap places w/ each other to form new compounds

• EX: AB + CD → AD + BC

• The inner elements combine and the outer elements combine to form new compounds

Combustion - A substance (usually a hydrocarbon) reacts w/ oxygen to produce heat, light, and typically produces carbon dioxide and water

• EX: C_xH_y + CO₂ → CO₂ + H₂O + Fire

• Hallmark sign of combustion: The second reactant is oxygen and the products are carbon dioxide and water

Balancing chemical reactions - Reactants are the same exact # as your products

• Save oxygen & hydrogen balancing for last

Moles

Moles - Units of measurement that is the amount of pure substance containing the same # of chemical units

• Mole = 6.022 × 10²³ → Avogadro’s #

To calculate the molar mass, multiply the amount of elements by the element’s mass and add them all together

• EX: C6H8O6 = (6×12) + (8×1) + (6 × 16) = 176 g/mol

Factors that Affect Chemical Reactions

Collision Theory - for particles to react, they have to collide w/ each other w/ sufficient energy (activation energy)

Amount of energy of particles:

• More energy → more energy they transfer when they collide

• less energy → nothing will happen, unable to reach activation energy

Temperature:

• higher rate of reactions

• Particles gain more energy → particles move faster & collide harder/more often → more likely to exceed activation energy

Concentration/pressure:

• How many particles per unit of volume

• More particles per unit of volume → collide more frequently → higher rate of successful collisions

Surface area:

• More surface area facilitates more collisions between atoms → higher rate of successful collisions

Catalyst - Higher rate of reaction w/ less energy

• Substances that speed up a reaction w/out being used up in the reactions themselves

• An alternate reaction pathway

Exothermic reactions - energy/heat is released at the reaction

• Combustion reactions

• Oxidation reactions

• Neutralization

Endothermic reactions - Takes in heat energy from the surroundings. Absorbs heat

• Photosynthesis

• Cooking an egg

• Liquid evaporation

Equilibrium - When the rate of the forward reaction equals the rate of the reverse reaction in a closed system

• Reactant 1 + reactant 2 → product

• Reactant 1 + reactant 2 ← product

Static equilibrium - The forward and reverse reaction are occuring at the same time

• Continuously happening

Properties of Solutions

• Polarity of Water

  • Adhesion - Binding or attraction between dissimilar molecules, atoms, surfaces, and substances

  • Cohesion - Attraction of molecules for other molecules of the same kind

Solution - A homogeneous mixture of one or more solutes dissolved in a solvent

Homogeneous mixture - when the solutes, such as salt, is completely dissolved in the solvent, such as water. Not easily separated

Heterogeneous mixture - the solute and solvents are still easily separated such as pebbles in water

Solutes - A substance that can be dissolved into a solution by a solvent and is present in smaller amounts

Solvent - A substance with the ability to dissolve other substances to form a solution and is present in larger amounts

Water is called the universal solvent because it is capable of dissolving more substances than any other liquid

Polar substances - soluble in water

Non-polar substances - not soluble in water

Molarity - # of moles of solutes per one liter of solution

• M = moles/liter

Dilution - process of reducing the concentration of a solute in a solution by adding more solvent

Hypertonic - has a higher solute concentration. Solutes flow out

Hypotonic - has a lower solute concentration. Solutes flow in

Isotonic - contains the same concentration of water and solutes

• No osmotic flow

Osmosis - diffusion of solvent molecules (water) through a selectively permeable membrane from a region of high water potential to a region of lower water potential

Factors affecting diffusion:

• Distance - the greater the distance, the slower the diffusion rate

• Temperature - Higher temperature causes an increase in diffusion rate

• Solvent characteristics - Increased density can slow molecules down, decreasing diffusion

• Traveling characteristics - The greater the mass, the lower the diffusion rate

• Barrier characteristics - small non-polar cells pass through the barriers more easily

Acid and Bases

A measure of how acidic or alkaline a solution is

Acid - substances that increase concentration of hydrogen ions (H+)

Base - substances that decrease concentration of hydrogen ions (H+)

Measuring pH:

• Wide range indicator - chemical compound that changes color based on pH

  • Color corresponds to pH level such as red for acidic or blue for alkaline

• Universal indicator - color range from deep red in very acidic to blue/purple to very alkaline

  • Type of wide range indicator

• Litmus paper

  • Blue litmus paper turn red under acidic conditions

  • Red litmus paper turn blue under alkaline conditions

• pH probe - gives more accurate readings of pH

When acids and bases are mixed, they undergo neutralization

• Typically results in salt or water

o

Acids often tend in -ic such as hydrochloric acid

Bases often end in -oxide or -nate such as sodium hydroxide or calcium carbonate