Studied by 0 people
What do periods represent
The highest occupied energy level of an element
State the properties of metals
good conductors of heat
Malleable
Ductile
Shiny
Tend to los electrons
State the properties of nonmetals
Poor conductors of heat and electricity
tend to gain electrons
Can be solid liquid or gas
State the properties of metalloids
both metallic and nonmetallic properties
Some of them are great superconductors (conduct electricity at high temp)
Where are transition metals found
F block (groups 3 - 11)
Why does Zeff increase from left to right in a period
Number of protons crease while number of shielding electrons stays the same
charge felt by e- increases
Why does zeff decreases as you go down a group
More shielding electrons and same number of protons
Formula for Zeff
Zeff = # of p - inner shell electrons
How does ionic radius of n anion change when adding an electron
Size increases (less Zeff per electron)
How doese in=onic radius of a cation change when removing an electron
Decreases
What is an isoelectronic species
They have the se number of electrons
Describe the size trend for isoelectronic species
As atomic # increases ionic radius decreases due to effective nuclear charge
How does EA and IE change with Zeff
As effective nuclear charge increases so does IE and EA
Why do metals tend to lose electrons
They have low IE values
Why do nonmetals gain electrons
They have high EA values
State the chemical and physical properties of alkali metals
Good conductors of electricity
low density
Very reactive
From ionic compounds with nm
properties of halogens
Coloured
Very reactive nm
Can form ionic compounds or covalent compounds
Explain the trend in displacement of halogens
A halogen can be displaced by the one above it because they get more reactive as they get smaller
Describe noble gasses
They are colourless gasses that exist as single atoms
State the trend in melting points down group 1
They decrease down group one as zeff
State the trend in melting points down group 17
Melting points increase down group 17 because the molecular structure held together by LDFs which increase in strength with size
Explain the trend in melting points across a period
Increase until group 14 and then decrease to a minimum at group 18 (metallic bonds increase with # of e- then decrease as it gets to nms)
What is an oxide
Oxides are formed from an element and oxygen
Product of a metal oxide + water
Metal hydroxides (basic)
Nonmetal oxides and water product
Acids
What is an ionic bond
The electrostatic attraction experienced between the electric charges of a cation and an ion
What is a transition elements
They have electronic configurations that allow them to lose different amounts of electrons from their d sub levels (variable oxidation states)
What is the structure of an ionic compound under normal conditions
Lattice
Why are ionic compounds found in a lattice structure
Because their ions are attracted to ions of the opposite charge causing them to form three dimensional crystalline structures
What does lattice enthalpy depend on
Size and charge
What does the coordination number represent
The number of ions surrounding a given ion in the lattice
Why do ionic compounds have high mp and bps
Strong forces of attraction and thus a large amount of energy needed to break the lattice
When do ionic compounds conduct electricity
In the molten state they have mobile ions
Explain the solubility of ionic compounds
They are mostly soluble in water as they can dissociate into component ions
Explain the volatility of ionic compounds
Low volatility due to strong electrostatic attraction
Explain the brittleness of ionic compounds (solid)
Very brittle because ions of like charge are close to each other in the lattice
Compare change in electronegativity values of ionic, covalent, and metallic bonds
Ionic: X > 1.8
Polar covalent: 0< X < 1.8
Non-polar covalent: X = 0
Metallic: low
What is a covalent bond
Results from the simultaneous attraction of two positive nuclei to the same shared pair of electrons
State the trend between bond strength and bond length
The longer the bonds are the less strong the are due to increased electrostatic attraction
Length: single > double > triple
What does electronegativity represent
The measure of the ability of an atom to attract. Pair of covalently bonded electrons
What is a dipole moment
The slightly imbalance in charge in a polar bond
Is there a dipole moment in a nonpolar
No
Sate the NASL method
N: electrons needed to fulfill octet rule ( H= 2, Be = 4, B = 6)
A: available electrons
S: shared (N - A) dvided by two to determine number of bonds
L: lone pairs (what’s leftover)
What does formal charge do
Determines if an atom is positive negative or neutral
Formal charge formula
FC = valence e - (nonbonded e- + # of bonds)
Explain VSEPR theory
Electron domains are located so that they feel the minimum repulsive force
the number and identity of electron domains predicts the shape of the molecule
Define non polar molecule
A molecule that has no net dipole
Steps for determining molecular polarity
draw VSEPR
Determine if it is symmetrical or if it has uniform atoms surrounding it
What is a Resonance structure
Describes structures that have multiple ways to depict the same molecule
What is a crystal
A single molecule with a repeating pattern of covalent bonds
What is a covalent network solid
A crystalline structure linked together with covalent bonds
State the properties of a covalent network
Conductivity: poor because there are no delocalized electrons
Solubility: typically insoluble
Melting point: high
Hardness: high
What is an allotrope
Different structural modifications of the same element that can differ in chemical and physical properties
Graphite properties
Structure: trigonal planar
Electrical conductivity: yes
Thermal conductivity: low
Hybridization: sp²
Diamond properties
Structure: tetrahedral
Electrical conductivity: no
Thermal conductivity: high
Hybridization: sp³
Graphene properties
Structure: single planar
Electrical conductivity: yes
Thermal conductivity: high
Hybridization: sp²
What is Quartz
SiO2
Giant covalent structure (tetrahedral)
Very strong structure with low conductivity and high mp
What is coordinate covalent bonding
The shared pair of electrons is donated from one of the two atoms
What are dipole - dipole IMFs
Forces that occur from the interaction between a partially positive and partially negative dipole
What is hydrogen bonding
a kind of dipol-dipole interaction that occurs between hydrogen atoms and O, N, F atoms in covalent molecules
What are LDFs
Weak interactions between nonpolar covalent molecules caused by temporary dipoles (created by changes in electron distribution)
What is delocalization
When electrons are shared by more than two atoms in a molecule or ion
What is hybridization
Mixing atomic orbitals within an atom forming new molecular orbitals so that bonding can occur
What type of bonds are single bonds
Sigma bonds with end to end overlap
What are bonds other than the first bond
Pi bonds
side to side overlap
Describe the structure of metallic bonding
atoms give up their valence electrons and they are redistributed and shared by all in the delocalized see of electrons
What determines metallic bond strength
# of delocalized e-
Charge of the cation
Size of cation
What are alloys
Solid solutions
How are alloys possible
Because of the delocalized nature of electrons in a metallic bond the lattice can accommodate different sizes of cations
Why are alloys more stable
Because the different atoms in the lattice revert layers from sliding past eachother
What is bonding
A continuum between ionic covalent and metallic models
Oxidation state rules
All uncombined elements have an oxidation state of 0
Sum of all oxidation numbers in a compound is zero
The sum of oxidation numbers in an ion is equal to the charge
The oxidation numbers of oxygen is -2 usually
Oxidation # of hydrogen is usually +1
When is oxygen not an oxidation number of -2
peroxides
BaO2
Na2O2
ZnO2
When does hydrogen have an oxidation # of -1
Metal hydrides
Oxidizing agent
Causes the oxidation of another element and gets reduced
Reducing agent
causes the reduction of another element and is oxidized itself
How does the activity series work
Something above replaces something below
What is electrochem
Deals wth the interconversion of electrical energy and chemical energy
What type off of process is electrochemistry
Redox
Contrast voltaic and electrolytic cells
Voltaic: chemical E to electrical E spontaneous and exothermic
Electrolytic: electrical E to chemical E non-spontaneous
What is an electrode
A conductor of electricity used to make contact with a nonmetallic part of the circuit
Where does oxidation occur
At the anode
Where does reduction occur
At the cathode
Which electrode is positive in a voltaic cell
Cathode
Which electrode is positive in an electrolytic cell
The anode
What drives the spontaneous reaction
Negative free energy change
How do you determine which substances will be oxidized or reduced in a voltaic cell
Using the activity series (higher up = more easily oxidized)
What is the function of a salt bridge
Contains concentrated solution of a strong electrolyte and allows ions to diffuse out of it.
provides physical separation
Provides electrical continuity for anions and cations
What is the function of a battery in an electrolytic cell
Electron pump
What is electromotive force
The energy supplied by a source divided by the electric charge transported through the source
Cell potential
The potential difference (voltage) between the anode and cathode under SATP
Cell potential equation
Cell = Ecat - Ean
What assumption about the cathode is made to calculate e cell
That the cathode is the more positive value meaning the stronger oxidizing agent
What is E cell for a spontaneous process
Ecell > 0
What is the standard hydrogen electrode
Gaseous hydrogen at a pressure of 100 kkpa bubbled over a platinum electrode (0V reduction potential)
How are delta G and E cell related
When delta G is zero Ecell is 0
For electrolytic cells which reaction potential is more likely to react
The higher one
What is a battery
A portable electrochemical device that produces electricity and is made up of one or more voltaic cells in series containing both electrodes and electrolyte
What is an electrode in a battery
One of two metal terminals
What is the electrolyte in a battery
A solution or paste that conducts charge
