Recap from previous guides
Valence electrons are the outermost electrons.
Valence electrons are found in the s and p orbital of the outermost shell.
A gap in ionization energies could tell us how many valence electrons an element has.
From the periodic table, you could tell how many valence electrons an element has.
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From just the periodic table, you could tell that oxygen has 6 valence electrons and carbon has 4 valence electrons. This layout of the periodic table is also proof that elements in a group have very similar properties. Therefore, they tend to bond with similar elements and form similar compounds.
Before getting into bonds, it is also good to memorize the charges of most elements on the periodic table.
Image Courtesy of Chemistry Land
The transition metals aren't included here because they have various charges and very different properties. Don't worry though, the AP won't question you about them. At most, you would have to write their electron configurations.
There are three different types of elements: metals, nonmetals, and metalloids.
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Metals are good conductors of heat and electricity🔥⚡, shiny, malleable (can bend), and ductile (can be made into a wire).
Nonmetals are the complete opposite: bad conductors of heat and electricity and brittle.
Metalloids have properties of both metals and nonmetals.
Elements bond to achieve the lowest possible energy, where they are stable. There are two different types of bonds you should know: ionic bonds and covalent bonds.
Ionic bonds are formed by the transferring of electrons from one atom to another, usually a metal and nonmetal.
The atom that loses an electron will gain a positive charge and is called a cation (usually a metal).
The atom that gains an electron will gain a negative charge and is called an anion (usually a nonmetal).
Some properties of ionic compounds include very strong bonds, solubility in water, and the ability to strongly conduct heat and electricity.
Example - NaCl
In the ionic compound NaCl, Sodium (Na) loses an electron and gains a positive charge, while Chlorine (Cl) gains an electron and therefore obtains a negative charge.
The one valence electron that was in Na was transferred to the chlorine atom in order for both ions to have a full octet. Group 1 elements and group 17 elements (halogens) often bond this way to reach stability.
When they become ions, their electron configuration actually matches the one of the noble gas closest to it. Here is an example:
Covalent bonds are formed when atoms share electrons (usually two nonmetals).
Some properties of covalent bonds include low melting points and weak electroconductivity abilities.
There are actually two types of covalent bonds: polar covalent bonds and nonpolar covalent bonds.
Polar covalent bonds are a type of bonding where electrons are unequally shared between two different nonmetals.
Nonpolar covalent bonds are a type of bonding where electrons are equally shared between, usually, two of the same nonmetal.
Polar Example - HF
Hydrogen and Fluorine create a polar covalent bond. Fluorine attracts electrons more strongly due to its high electronegativity, resulting in an unequal distribution of electrons.
Image Courtesy of Study
The dash represents two shared electrons. Rather than a transfer of electrons, Hydrogen is sharing one electron and Fluorine is sharing one electron to lead to two full octets.
Nonpolar Example - Cl2
In the covalent compound Cl2, Chlorine atoms bond together to share the final electron that they need to become noble gases.
Image courtesy of Wayne Breslyn
They are both sharing one electron with each other to obtain the full octet but a nonpolar covalent bond is different since their electronegativities are the same.
Try these little questions on your own and see how you do! It's just to see how well you understood this key topic :)
Atoms of Ca combine with atoms of Br to form an ionic bond.
What ratio would they combine in?
What other compounds have this same ratio with Ca?
What elements could form an ionic bond with sulfur?
The compound: CaBr2 - This is because Ca has a +2 charge and Br has a -1 charge. In order for the two to bond together and form a neutral compound, there must be two Br atoms.
We need other elements that have a -1 charge in order for them to bond in this 1:2 ratio with calcium. This includes all of group 17 on the periodic table, which includes fluorine, chlorine, bromine, and iodine.
In a 1 to 1 ratio, any elements in group 2 would form an ionic bond with sulfur. Some examples include MgS, CaS, and BaS. In a 2 to 1 ratio, any elements in group 1 would form an ionic bond with sulfur. An example includes Na2S.
🎥Watch: AP Chemistry - Valence Electrons and Ionic Compounds
✍️ Free Response Questions
AP Chemistry Free Response Questions
⚛️ Unit 1: Atomic Structure and Properties
1.1Moles and Molar Mass
1.2Mass Spectroscopy of Elements
1.3Elemental Composition of Pure Substances
1.4Composition of Mixtures
1.5Atomic Structure and Electron Configurations
1.6Photoelectron Spectroscopy & Graph Interp.
🤓 Unit 2: Molecular and Ionic Compound Structures and Properties
2.0Unit 2 Overview: Molecular and Ionic Bonding
2.1Types of Chemical Bonds
2.2Intramolecular Force and Potential Energy
2.3Ionic Bonding and Ionic Solids
2.4Metallic Bonding and Alloys
2.5Lewis Dot Diagrams
2.6Resonance and Formal Charge
🌀 Unit 3: Intermolecular Forces and Properties
3.0Unit 3 Overview: Intermolecular Forces and Properties
3.2Properties of Solids
3.3Solids, Liquids, and Gases
3.4The Ideal Gas Law
3.5The Kinetic Molecular Theory of Gases
3.6Deviations from the Ideal Gas Law
3.7Mixtures and Solutions
3.8Representations of Solutions
3.9Separation of Solids/Mixtures
3.10Solubility and Solubility Rules
3.11Spectroscopy and the Electromagnetic Spectrum
3.12Quantum Mechanics and the Photoelectric Effect
🧪 Unit 4: Chemical Reactions
4.0Unit 4 Overview: Chemical Reactions
4.1Recognizing Chemical Reactions
4.2Net Ionic Equations
4.4Physical vs. Chemical Changes
4.5Stoichiometry & Calculations
4.6Titrations - Intro and Calculations
4.8Intro to Acid-Base Neutralization Reactions
👟 Unit 5: Kinetics
5.0Unit 5 Overview: Kinetics
5.1Defining Rate of Reaction
5.2Introduction to Rate Laws
5.3Rate and Concentration Change
5.4Writing Rate Laws
5.5Collision Model of Kinetics
5.6Reaction Energy and Graphs w/ Energy
5.7Reaction Mechanisms and Elementary Steps
5.8Writing Rate Laws Using Mechanisms
🔥 Unit 6: Thermodynamics
6.0 Unit 6 Overview: Thermochemistry and Reaction Thermodynamics
6.1Endothermic Processes vs. Exothermic Processes
6.2Energy Diagrams of Reactions
6.3Kinetic Energy, Heat Transfer, and Thermal Equilibrium
6.4Heat Capacity and Coffee-Cup Calorimetry
6.5Phase Changes and Energy
6.6Introduction to Enthalpy of Reaction
6.7Bond Enthalpy and Bond Dissociation Energy
6.8Enthalpies of Formation
⚖️ Unit 7: Equilibrium
🍊 Unit 8: Acids and Bases
8.0Unit 8 Overview: Acids and Bases
8.1Introduction to Acids and Bases
Unit 9: Applications of Thermodynamics
🤺 AP Chemistry Essentials
🧐 Multiple Choice Questions
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