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**Pictures of Chem Class ^_^
*General Suggestions for Student Pages
*Organic seminar sign-up
*Periodic Table Assignment
*Topic (I) --> Sign-up
*Topic (II) --> Review
*Topic (III) --> Stage of Page
*Unit 8 Topics
Aldehydes and Ketones
Alkenes and Alkynes
Amines and Amides
An overview of molarity problem
Atomic Mass and Avogadro's Hypothesis
atomic number and mass
Balancing Chemical Reaction Equations
Basic Science definitions.
Calculations involving the Mole and the Mass of a Substance and the Volume of a gas
Calculations involving the Mole and the Volume of a gas and the Number of Particles
Certain & Uncertain Digits, Defined Numbers and Accuracy & Precision
Chemical Equations and the Conservation Laws
Chemical families -- by Judy Bai
Classification of matter
Concentration of ions in Solution
Constructing the name of an Ionic Compound
Derived Quantities and Density
Early atomic models
Electrostatic forces, electron shells, Valence electrons and valence of an atom
Energy Changes in Chemical Reactions
Ethers and Carboxylic Acids
History of the period table
How to Classify Atoms and Ions
How to Read a Scale
INTERMOLECULAR FORCES AND BONDING
Introduction to functional groups and Alcohols---Elizabeth
Introduction to organic chemistry and hydrocarbon
Ionization energy, Electron Affinity, Atomic Radius
Isotopes and their mixtures
Lab safety 2
Later atomic models
Lewis Dot Diagrams of Neutral Atoms, Monatomic Ions,and Ionic Compounds
LIine spectra, electron shells and energy level diagrams
Mixing Two Solutions and Making Dilute Solutions
Molar Concentrations and Making up Solutions
Multiple conversions between moles,mass, volume and number of particles
Multiplying & Dividing and Adding and Subtracting with Sig Figs
Naming Hydrates and Naming Compounds Using the Prefix System
Naming Monatomic and Polyatomic Ions
Percent Yield and Purity
Phase Changes--by AnnYU
Phases, the Magic 7 and Chemical Word Equation
polar and nonpolar solvents
SI Units and Metric Unit conversions
Significant Figures & Zeros
Solutions and Solubility Introduction
Solving Problems that Involve Multiple Operations and Sig Figs
Stoichiometery calculation involvingMoles, Mass, Gas volume and Molecules
Stoichiometry Calculations Involving Molar Concentration
Stoichiometry of Excess Quantities
The Conductivity of Aqueous solutions
The Major divisions of the periodic table & Metals Non-metals and semi conductors
The Meaning of Stoichiometry and the Coefficients in a Reaction Equation
The Mole Concept and Finding Molar Mass
The nature of covalenting bonding & Predicting the formula of covalent bonds
The nature of solutions of ions
The Physical separation of substances
THE PHYSICCAL PROPERTIES OF MATTER
The role of Kinetic Energy in Phase Changes
TO DRAW A Lewis dot diagrams of covalent compounds
Types of Chemical Reactions - Combustion (Pt.2) &Summary
Types of Chemical Reactions - First 4 Types
Unbranched Alkanes and their Geometry
When to use each separation method
Writing electron configurations of atoms in full and core notation
Writing electron configurations of ions, and the copper and chromium exceptions
Electrostatic forces, electron shells, Valence electrons and valence of an atom
A:The electronic nature of chemical bonding
(a) The electronstatic forces between charged particles
what is an electronstatic force?
The electrostatic forces is the force that cause attraction and repulsion between two charged particles.
According to the electronstatic force:
- a positive charge particle and a negative charge particle attract ech other
- same charge particle repel each other
- as the distance of two particles are increasing, the attraction or the repulsion of two charged particles become smaller.
- if the charges on the two particles become larger, the attraction or repulsion of two particles become larger.
electstatic force explains the trends in pysical and chemical properties and it also explains the bonding between particles
(b) ELectron shellls
what is an electron shell?
each period on the periodic table is a different electron shell
The first electron shell which is the first row of periodic table has 2electrons.
The second electron shell which is the second row of the periodic table has 8 electrons.
what is an atomic radius of an atom?
the atomic radius of an atom is the the distance from the nucles of the atom to the outter shell
What should happen to the atomic radius going from left to the right of the periodic table?
the atomic radius will become smaller since the atomic number of the elements increase as well as the positive and the negative charge. According to the electrostatic forces' rules, the larger the charge, the larger the attraction between two charged particles. As the attraction is increasing, the atomic radius is becoming smaller.
The element Mg will have a larger atomic radius than Cl since Mg's atomic number is smaller, and the attraction between the nucleus and the electrons are smaller.
what shoud happen to the atomic radius going down a group?
the atomic radius becomes larger. As we going down a group of the peroidic table, the number of the electron shells increases since the atomic nunber of the atoms are increasing. Therefore, the atomic radius is becoming larger.
eg: Na will have a smaller atomic radius comparing to K because the element K will have more electron shells.
What is an open shell ?
It is a shell that can still contain more electrons
Q: What is a closed shell ?
It is the shell that cannot contain no more electrons
eg: The second electron shell which can hold maximum 8 electrons. The elements Be and N has the number of electrons less than 8 so their outermost shell is open. Ne has 8 electrons in the outermost shell so it's closed
(C) valence electrons
Q: What is the valence electrons?
they are electons in open shells.( Note that the "Valence" is used as an adj )
(note that the valence electrons of the noble gas can either be "8" or "0" since the valence shells of the nobel gases are full )
eg: Oxygen has six calence electrons. Fluorine has seven valence electrons
(d) The valence of an atom( The valence of the transition metals is not considered in this section )
Q:how valence electrons are put into the the orbitals
--each orbital can hold maximun two electrons.
--each electron added is going to a new orbital becacuse electrons repel each other.
--after there are one electron in each orbital, the electron that is going to be added will go to the orbital that already contained one electron, and be paired.
eg: Oxygen has six valence electrons. Carbon has four electrons.
Q: What is the valence of an atom? (we don't consider the transition metals)
The valence of an atom is the number of the unpaired electrons of an atom, and valence is sometimes called combining capacity. The "Valence" here is used as a noun.
Valence of an atom
The valence of oxygen is two. The valence of Carbon is four.
Exercise for the concepts:
1. which one has larger atomic radius, Cr or Zn? Explain your answer.
2. Which one has a larger atomic radius, Ca or Ra? Explain your answer.
3.which family of elements appears to possess only closed shells? (tex. P166#43)
4.How many electrons does Ca2+ has? Is the ion has an open shell or closed shell?
5. How many valence electrons does Mg have? What is the valence of Mg?
6.How many valence electrons does Cl have? What is the velence of Cl?
answers for the exercise:
1.Cr has a larger atomic answer comparing to Zn because Cr has a larger atomic number than Zn which means that the attraction between the nucleus and electrons is smaller. According to the rules of electrostatic forces, the smaller the attraction, the larger the distance.
2.Ra has a larger atomic radius because Ra has more electron shells comparing to Ca, therefore, it has a larger atomic radius.
3.The noble gases has closed shells because they all have eight electrons at their outermost shells.
4.Ca2+ loses 2 electrons comparing to Ca so it has eight electrons at the outermost shell, therefore, it has closed shell.
5.Mg has two valence electrons, and the valence of Mg is 2
6.Cl has seven valence electrons, and the valence of Cl is 1
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