Mats Lecture 5 Flashcards
Atomic Structure
How is the number of protons represented?
Z
What is the Atomic Mass Number?
A=N+Z
It is the total of neautrons and protons
What are primary bonds?
Relatively Strong Bonds
List the primary bonds
-Metallic Bonds
-Covalent Bonds
-Ionic Bonds
What is a secondary bond?
Van Der Waals Bond
How do metallic bonds work?
-Electropositive atoms donate their valence electrons to form a sea of electrons that are surrounding the atoms
-The positively charged ion cores are held together by mutual attraction to the electrons
-This results in strong metallic bonds
How do metals specific bonding affect its properties?
-Their valence electrons are not fixed
-Under an applied voltage, the valance electrons move which causes a current (they are good conductors of electricity)
-Metallic bonds are non-directional resulting in good ductility
-Metals have high melting points
What are covalent bonds?
The sharing of valence electrons among two or more atoms
-These bonds form specific angles for different materials
What are properties of materials formed by covalent bonds?
-Covalent bonds are very strong which results in hard materials
-Solid materials exhibit very high melting points
-Have limited ductility because the bonds are directional
-Electrical conductivity is not high
What are ionic bonds?
-When an atom donates a valance electron to a different atom, filling the outer energy shell of the second atom
What happens to the atoms once an ionic bond is formed?
-The atoms gain an electrical charge once filling (or emptying) their outer shell
What is the atom with a net positive charge called?
-Cation
What is the atom with a net negative charge called?
Anion
What are examples of materials with covalent bonds?
-Diamonds
-Sillicon Carbide
-Sillicon Nitride
-Boron Nitride
What are Van Der Waals Bonds?
Molecules or atoms in which there is either an induced or permanent dipole moment attract eachother
What is the definition of interatomic spacing?
How close two isolated entities are
What does a force and interatomic graph tell us about the attractive force between two entities? Why?
-It increases significantly as the distance between the two entities decrease
-The electrons of the two entities is attracted to the protons of the other entity
What does a force and interatomic graph tell us about the repulsive force between two entities? Why?
-It increases significantly as the distance between the two entities decrease
-The electron clouds of the two entities repel one another as they get closer
What does a force and interatomic graph tell us about the net force on the graph?
-The point at which the graph is zero means that the net force is zero
-This is the point where the entities are balanced (equilibrium)
What happens if you take the integral of the force and interatomic graph?
-You get the energy
What happens in the energy and interatomic graph when the force and interatomic graph reaches the point at which it’s zero?
the force=0 is the low point in the energy graph
-The lowest energy is where the two entities are the most stable
Why is the equilibrium bond energy (binding energy) important?
-It is the energy needed to create or break the bond
-This affects the melting point of the materials
