Chem part 2

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

1. All uncombined elements have an oxidation state of 0

2. Sum of all oxidation numbers in a compound is zero

3. The sum of oxidation numbers in an ion is equal to the charge

4. The oxidation numbers of oxygen is -2 usually

5. 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