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Modern Atomic Theory Review

Modern Atomic Theory

Electron

A negatively charged particle located in the volume of space surrounding the nucleus of an atom.

Neutron

A neutral particle located in the nucleus of an atom.

Proton

A positively charged particle located in the nucleus of an atom.

Cation (+):

One or more atoms that has lost an electron(s).

A main group METAL will LOSE electrons to form a CATION with the same number of electrons as the nearest noble gas.

Isotopes:

Are atoms of the same type that have a different number of neutrons.
Isotopes of elements are distinguished by the mass number (A).

Anion (-):

Elements that have unpredictable properties.

A main group NONMETAL will GAIN electrons to form an ANION with the same number of electrons as the nearest noble gas.

Atomic Mass:

Is the weighted average of isotopic masses based on the natural abundance of each isotope.
The natural abundance is the relative amount of each isotope found in a natural sample of any element. Natural abundance is relatively constant and unique for each element.

We know:

Isotopes are atoms of the same type that have a different number of neutrons.
The mass of an atom is dictated by the mass of protons and neutrons because the mass of an electron is negligible in comparison.

Atomic Mass Calculations:

Atomic mass for an element can be calculated with the following formula:

$$\sum_{n} \text{(fraction of isotope n) x (mass of isotope n)}$$

In simple terms this formula is telling us that atomic mass can be calculated by:

1.
Multiplying each isotopic mass of an element by its relative abundance.

2.
Adding the resulting masses of the isotopes together.

Defining the Mole:

The mole is defined using the C-12 isotope.

One mole = number of atoms in exactly 12 g C-12.

12 g of C-12 = 1 mole of C-12 atoms = exactly $6.02$x$10^{23}$ C-12 atoms

The mass of one mole of C-12 atoms is 12 g

1 mole of carbon (C) $6.02$x$10^{23}$ atoms = Avogadro's number

Periodic Trends

Metals:

Generally good conductors of heat and electricity

Tend to lose electrons in a chemical reaction

Non-Metals:

Generally poor conductors of heat and electricity

Tend to gain electrons in a chemical reaction

Metalloids:

Have properties of both metals and non-metals.

Main Group:

Elements that have predictable properties

Transition Metals:

Elements that have unpredictable properties.

Lanthanoids and Actinoids:

Elements that are placed separately for a more compact periodic table. They have similar properties to the elements lanthanum and actinium.

Groups:

Each column in the periodic table is called a group and numbered 1-18

Each row in the periodic table is called a row and numbered 1-7

Elements in a group have similar properties

The noble gasses in group 18 are relatively unreactive.

Atomic Structure

Orbital:

The likely position of an electron in an atom described by a probability distribution map.

Spin Quantum Number $m_{s}$

Spin is intrinsic to all electrons, it is quantized, with only two orientations; spin up or spin down.

Value $=+\frac{1}{2}$ OR $-\frac{1}{2}$

When:
n=1, l=0: 1s
n=2, l=0,1: 2s,2p

Principal Quantum Number (n)

Orbital’s size and energy level of an electron.

A whole number 1,2,3,4…..

n increases with an electron’s energy and distance from the nucleus.

Each level is called a shell.

Angular Momentum Quantum Number (l)

The shape of an orbital.

0,1,2,3,…,n-1

Each value for l is a subshell

Each number value of l is assigned a letter s,p,d,f,g….

When:
n=1, l=0: 1s
n=2, l=0,1: 2s,2p

Magnetic Quantum Number $m_{l}$

Orientation of orbital in 3D space.

Value= integer values from –l…l.

There are 2(l)+1 values of $m_{l}$ for each value of l.

Examples:
When:
l=0, $m_{l}$ = 0
l=1, $m_{l}$ = -1,0,1
2(0)+1=1 value of $m_{l}$
2(1)+1=3 values $m_{l}$

Orbital Shapes

Orbital Shapes = Angular Momentum Number (l)

Values of (l) angular momentum
Number	Letter
0	s
1	p
2	d
3	f
4	g

Letter values continue according to the alphabet after f, with the exception of J.

s,p,d,f,g,h,i,k,….. Sober Physicists Don’t Find Giraffes Hiding In Kitchens

Pauli Exclusion Principle

No two electrons in an atom can have the same four quantum numbers. But.. Any three quantum numbers can be the same.

This implies: One orbital may contain two electrons of opposite spin orientation!

Single electron atom

Multi-electron atom

Aufbau Principle

Electrons occupy lower energy orbitals before filling higher energy orbitals.

Hund’s Rule

Electrons will singly occupy degenerate orbitals until they are half full before pairing up with other electrons. Electrons in half full orbitals will have the same spin.

Building the World Review

Quantifying Chemical Compounds

The Law of Multiple Porportions

Elements combine in different ways to form substances whose mass ratios are small whole number multiples of each other.

The Law of Definite Proportions

All samples of a pure chemical substance always contain the same proportion of elements by mass regardless of their origin.

By mass, Carbon dioxide (CO$_2$ is: 73% Oxygen and 27% Carbon

All carbon dioxide is chemically the same in every location.

pure chemical substances are chemically the same

Empirical Formula

The lowest whole integer numbers representing an atomic ratio of a molecule using a chemical description.

Empirical Formula of hydrogen peroxide: HO

Molecular Formula:

A chemical description of the actual complete molecule.

Molecular Formula of hydrogen peroxide: $H_{2}O_{2}$

Molecules and the Mole:

One mole is equal to $6.022$ x $10^{23}$ objects.
One mole of any compound is equal to the sum of the molar masses of all elements in the compound.
1 mole of carbon dioxide $CO_{2}$ a mass of : $12.01\,g + 16.00\,g + 16.00\,g = 44.01\,g$

Periodic Trends:

The periodic table is organized to help us determine useful information about elements. For example: atomic radius, electronegativity, and ionization energy. Learning periodic trends can help us understand why certain elements have the properties we observe.

Electronegativity

The ability of a bonded atom to attract electrons

Moving down a column on the periodic table electronegativity decreases

Moving across a row on the periodic table electronegativity increases

The difference in electronegativity determines bond type

Electronegativity differences (ΔEN) for bonded atoms can be calculated by subtracting the least electronegative atom from the atom with the highest electronegativity.

For hydrochloric acid (HCl):
Electronegativity of Cl=3.0
Electronegativity of H=2.1
∆𝐄𝐍=𝟑.𝟎-𝟐.𝟏=𝟎.𝟗

Atomic Radius

Is the bonding radius determined from averaging measurements of many compounds and molecules

The bond length of a two bonded atoms is determined by adding their bond radii

Moving down a column on the periodic table the principle quantum number (n) of the outermost electrons increases, orbitals are larger, therefore the atomic radii are larger.

Moving across a row the electrons in the outermost shell feel the charge from the nucleus more strongly. Electrons are closer to the nucleus, orbitals are smaller, therefore the radii are smaller

On the periodic table bond radius increases down a column.

On the periodic table bond radius decreases across a row.

Atomic Radius and Ions:

An atom that has lost an electron (cation) will have a smaller radius than the neutral atom. Fewer electrons = smaller electron cloud = smaller ionic radius.

An atom that has gained an election (anion) will have a larger radius than the neutral atom. More electrons = larger electron cloud = larger ionic radius.

Cations have a smaller ionic radius than the neutral atom.

Anions have a larger ionic radius than the neutral atom.

Ionization Energy

The amount of energy required to remove one electron from an atom (or ion) in a gaseous state.

Moving down a column on the periodic table the principle quantum number (n) of the outermost electrons increase, orbitals are larger, therefore it takes less energy to remove an electron because they are farther from the nucleus.

Moving across a row the electrons in the outermost shell feel the charge from the nucleus more strongly, orbitals are smaller, therefore it takes more energy to remove an electron because they are closer to the nucleus.

On the periodic table ionization energy decreases down a column.

On the periodic table ionization energy increases across a row.

Chemical Bonding

Chemical Bonding Terminology

Click/tap on the picture to view a definition.

Classes of Chemical Bonding

Ionic

Electrostatic attraction between positive and negative ions.

Bonding atoms are generally metals and non-metals.

Electron is transferred from one element to another.

Ionic Bonding in Sodium Chloride (NaCl)

Covalent

Electron sharing between atoms.

Bonding atoms are nonmetals.

Electrons are equally shared by atoms.

Covalent Bonding in Hydrogen (H2)

Polar Covalent

Electron sharing between atoms.

Bonding atoms are nonmetals.

Electrons are unevenly shared between atoms.

Polar Covalent Bonding in Hydrogen Fluoride (HF)

Electronegativity and Bond Types

The electronegativity difference (ΔEN) between bonded atoms can be used to identify which type of bond exists in a molecule

Electronegativity Differences and Bond Type

(ΔEN)	Bond Type	Example
0.0-0.4	Covalent (no charge on atoms)	$O_{2}$ Oxygen
0.4-2.0	Polar Covalent (partial charge on atoms)	CO Carbon Monoxide
2.0 +	Ionic (full charge on ions)	KI Potassium Iodide

Valence Electrons and Bonding

We know:

Valence electrons are the electrons in the outermost shell of an atom.

Valence Electrons:

The valence electrons are the electrons involved in chemical bonding between atoms.
The number of valence electrons an element has determines the chemical properties of that element.
Elements in a column (group) have the same number of valence electrons, this is why elements in a group have similar chemistry.

Valence Electrons Continued:

The valence electrons of a main group element are located in the outermost shell.
The valence electrons of a transition metal are located in the outermost d orbitals, as well as the outermost shell.

Valence electrons are responsible for the chemical properties of an atom.

Lewis Structures

Lewis Structures:

Representing the valence electrons of a main group element using dots surrounding the chemical symbol.

Lewis Theory:

Chemical bonding is the attainment of a stable electron configuration through the sharing or transfer of electrons.
Lewis Theory uses the octet rule to predict bonding.
Lewis structures can be used to demonstrate bonding in molecules by showing atoms in a molecule sharing electrons to attain a full octet.

Octet:

A full outer shell containing eight electrons.

The Octet Rule

A stable electron configuration can be attained with eight electrons in the outermost shell.
Bonding atoms will transfer or share electrons to satisfy the octet rule, each atom will have access to eight electrons in its outermost shell.
The octet rule can be used to predict how atoms bond.

This rule only works for the second period (row) of the periodic table.
Elements beyond the second row can access d or f orbitals, elements are larger and have more room for bonding.

Hyper-coordination: Elements beyond the second row (after Neon) can have expanded octets.
The octet rule is a useful tool for predicting bonding in molecules especially in organic chemistry.

Lewis Structures Terminology

Formal Charge:

The charge on an atom in a Lewis structure, assuming all electrons are shared equally. Formal charge is calculated with the following formula:

(valence $e^{-}$) - ($\frac{1}{2}$bonding $e^{-}$) - (lone electrons) = Formal Charge

Formal charge is used to determine the best Lewis structure for a compound that has more than one choice. The lowest possible charge indicates the most energetically favorable structure.

Resonance Structures:

When more than one Lewis structure is allowed for a compound drawing both structures with a double headed arrow between them is the correct way to indicate resonance.

Transformations of Matter Review

Working with Chemical Equations

Chemical Reactions Terminology

Terminology:

Law of Conservation of Mass:

In a chemical reaction atoms are rearranged through the making and breaking chemical bonds, atoms are not altered or destroyed.

In a chemical reaction the mass of the products equals the mass of the reactants.

Law of Conservation of Mass: In a chemical reaction mass is neither created or destroyed.

Balancing Chemical Reactions

We Know:

All atoms in the reactants must be accounted for in the products! (Conservation of mass).

Chemical reactions are written as reaction equations.

Balancing Chemical Equations:

Reaction equations must be balanced to account for all the products and reactants in the chemical reaction.

Balancing Chemical Reactions Guide:

1.

Write out the skeletal equation.

$Fe_{(s)} + O_{2(g)} \to Fe_{2}O_{3(s)} $

2.

Balance atoms that appear in more complex molecules first.

$Fe_{(s)} + $$3O_{2(g)}$ $\to$$2$$Fe_{2}$ $O_{3(s)}$

Balance oxygen first.

3.

Balance Atoms that appear as free elements.

$4Fe_{(s)} + $ $3O_{2(g)} \to $$2Fe_{2}$$O_{3(s)}$

Balance iron.

4.

Check:

Left Side
4 Iron
6 Oxygen

Right Side
4 Iron
6 Oxygen

Chemical Reaction Types

Different Chemical Reaction Types

Precipitation

Precipitation of lead (II) iodide:

2 $KI_{aq}$ + Pb$(NO_{3})_{2(aq)}$ → 2KNO$_{3(aq)}$ + Pbl$_{2(s)}$

Combustion

When a reactant combines with oxygen to form one or more compounds containing oxygen.

Acid Base

Arrhenius Acid

A substance that produces H+ in an aqueous solution, strong acids completely dissociate in aqueous solution.

$HCl_{(s)}$ + $H_{2}O_{(l)}$ → $H^{+}_{(aq)}$ + $Cl^{-}_{(aq)}$

Arrhenius Base

A substance in an aqueous solution that produces OH-, strong bases completely dissociate in aqueous solution.

$NaOH_{(aq)}$ + $H_{2}O_{(l)}$ → $OH^{-}_{(aq)}$ + $Na^{+}_{(aq)}$

Hydronium ion:

The ion formed when a proton associates with water to form $H_{3}O^{+}$.

$H^{+}_{(aq)}$ + $H_{2}O_{(l)}$ → $H_{3}O^{+}_{(aq)}$

Oxidation State Rules:

Rules must be followed in order! Rule 1 takes precedence over Rule 2 etc...

1.

The oxidation of an atom in an elemental state is zero (0).

2.

Monoatomic ions have an oxidation state is equal to the ion’s charge.

3.

For compounds, the SUM of the oxidation states of all atoms in:
i. A neutral molecule is zero (0).
ii. A polyatomic ion is equal to the sum of the ion’s charge.

4.

Metals in compounds have positive oxidation states.
i. Group 1 metals have an oxidation state of (+1).
ii. Group 2 metals have an oxidation state of (+2).

5.

Hydrogen generally has a (+1) oxidation state.

6.

In compounds non-metals generally have negative oxidation states:
i. Fluorine always has a (-1) oxidation state.
ii. The remaining group 17 elements generally have a (-1) oxidation state.
iii. Oxygen generally has an oxidation state of (-2).
iv. The remaining group 16 elements generally have an oxidation sate of (-2).
v. Group 15 elements generally have an oxidation state of (-3).

For elements not covered in the rules, use rule three to determine the oxidation state once all other oxidations states have been assigned.

Chemical Equilibrium Concepts

Certain reactions are reversible and can proceed in the forward and reverse directions.

The number of forward reactions occurring could initially be fast and numerous.

Over time the chances of the reverse reaction occurring increases with the increased amount of products formed.

Eventually a point in time will be reached when the forward reactions equal the reverse reactions.

When a reaction has reached equilibrium it has not stopped, the forward and reverse reactions are continually occurring.

When the number of reactions per unit of time (rate) of forward reactions is equal to the number of reverse reactions per unit of time (rate) the system is said to be in dynamic equilibrium.

When a system has reached dynamic equilibrium the concentrations of the products and reactants do not change. (This does not mean the concentrations are equal to each other!)

Module 2 Summary

Take the Test

Test can be retaken

You have exactly one mole of an unidentified elemental sample. The mass of this sample is 9 g The element is:

A)

B)

C)

D)

You have exactly one mole of an unidentified elemental sample. The mass of this sample is 108 g The element is:

A)

B)

C)

D)

You have exactly one mole of an unidentified elemental sample. The mass of this sample is 28 g The element is:

A)

B)

C)

D)

You have exactly one mole of an unidentified elemental sample. The mass of this sample is 14 g The element is:

A)

B)

C)

D)

You have exactly one mole of an unidentified elemental sample. The mass of this sample is 23 g The element is:

A)

B)

C)

D)

You have exactly one mole of an unidentified elemental sample. The mass of this sample is 40 g The element is:

A)

B)

C)

D)

Which has more atoms one gram of helium or one gram of neon?

A)

B)

Choose the correct statement about quantum numbers.

n = principal quantum number, n = 0,1, 2, 3, ......

l = angular momentum quantum number, l = 1, 2, 3, ... , (n+1)

ml = magnetic quantum number, ml = (-l), .... , 0, .... , (+l)

ms = spin quantum number, ms = +1 or -1

Select the correct ground state electron configuration for arsenic.

1s\(^{2}\) 2s\(^{2}\) 2p\(^{6}\) 3s\(^{2}\) 3p\(^{6}\) 4s\(^{2}\) 3d\(^{10}\) 4p\(^{3}\)

1s\(^{2}\) 2s\(^{2}\) 2p\(^{6}\) 3s\(^{2}\) 3p\(^{6}\) 3d\(^{12}\) 4s\(^{2}\) 4p\(^{1}\)

1s\(^{2}\) 2s\(^{2}\) 2p\(^{6}\) 3s\(^{2}\) 3p\(^{6}\) 4s\(^{2}\) 3d\(^{8}\) 4p\(^{5}\)

[Kr] 4s\(^{2}\) 4p\(^{1}\)

How many moles of oxygen are in a 1.03 gram sample of dopamine (C\(_{8}\)H\(_{11}\)O\(_{2}\)N)?

1.91×10\(^{-3}\) mols O

10.34×10\(^{-8}\) mols O

2.86×10\(^{-2}\) mols O

1.34×10\(^{-2}\) mols O

Choose the most appropriate Lewis structure for hydrogen cyanide (HCN)?

Which of the following compounds has an ionic bond?

A)

B)

C)

D)

Choose the correct balanced equation for the reaction of aluminum chloride with silver nitrate. AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\) → Al(NO\(_{3}\)) \(_{3(s)}\) + AgCl \(_{(aq)}\)

AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\) → Al(NO) \(_{3(s)}\) + AgCl \(_{3(aq)}\)

AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\) → AlNO \(_{3(s)}\) + AgCl \(_{3(aq)}\)

AlCl\(_{3(aq)}\) + 3AgNO\(_{3(aq)}\) → Al(NO\(_{3}\)) \(_{3(s)}\) + 3AgCl \(_{(aq)}\)

AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\) → Al(NO\(_{3}\)) \(_{3(s)}\) + 3AgCl \(_{(aq)}\)

Sodium bromide is the limiting reagent; 60 g of sodium bromide is the maximum amount that could be produced.

Sulfuric acid is the limiting reagent; 95 g of sulfuric acid is the maximum amount that could be produced.

Sodium bromide is the limiting reagent; 55 g of butyl bromide is the maximum amount that could be produced.

Butanol is the limiting reagent; 75 g of butyl bromide is the maximum amount that could be produced.

A)

B)

C)

D)

Choose the correct oxidation numbers for the V, O and Cl atoms in VOCl\(_{3}\).

A)

B)

C)

D)

Module 2 Test

Your current score is out of 16

Or

Review Module 2 Material

Modern Atomic Theory

You have exactly one mole of an unidentified elemental sample. The mass of this sample is
9 g
The element is:

You have exactly one mole of an unidentified elemental sample. The mass of this sample is
108 g
The element is:

You have exactly one mole of an unidentified elemental sample. The mass of this sample is
28 g
The element is:

You have exactly one mole of an unidentified elemental sample. The mass of this sample is
14 g
The element is:

You have exactly one mole of an unidentified elemental sample. The mass of this sample is
23 g
The element is:

You have exactly one mole of an unidentified elemental sample. The mass of this sample is
40 g
The element is:

Choose the correct balanced equation for the reaction of aluminum chloride with silver nitrate.

AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\) → Al(NO\(_{3}\)) \(_{3(s)}\) + AgCl \(_{(aq)}\)

AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\)
→
Al(NO) \(_{3(s)}\) + AgCl \(_{3(aq)}\)

AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\)
→
AlNO \(_{3(s)}\) + AgCl \(_{3(aq)}\)

AlCl\(_{3(aq)}\) + 3AgNO\(_{3(aq)}\)
→
Al(NO\(_{3}\)) \(_{3(s)}\) + 3AgCl \(_{(aq)}\)

AlCl\(_{3(aq)}\) + AgNO\(_{3(aq)}\)
→
Al(NO\(_{3}\)) \(_{3(s)}\) + 3AgCl \(_{(aq)}\)

Your current score is

out of 16

Letter values continue according to the alphabet after f, with the exception of J.

s,p,d,f,g,h,i,k,….. Sober Physicists Don’t Find Giraffes Hiding In Kitchens

Cations have a smaller ionic radius than the neutral atom.

Anions have a larger ionic radius than the neutral atom.