Unit 1: Chemical Bonds and Forces

Question 1

Timeline of historical figures related to the atom?

Answer 1

Democritus and Leucippius. Plato. Aristotle. Alchemists. John Dalton. Sir Joseph John Thomson. Ernest Rutherford. Niels Bohr. Louis de Broglie. Heisenberg. Erwin Schrodinger.

Question 2

What are Lewis Dot Diagrams?

Answer 2

They use dots around compound symbols to signify the number of electrons and how they are bonded.

Molecular compounds just use dots and symbols, sometimes the pairs formed between atoms form double bonds.

Ionic compounds use square brackets and a more equation-like diagram. Ex, MgCl2 would look like Mg with a +2 in the top right followed by [Cl] with a 2 in the bottom right and a -1 in the top right. Square brackets are needed whenever there is more than one atom of an element. Draw the products side elements with their changed electrons.

Question 3

What is a structural diagram?

Answer 3

Use lines to show the bonds between atoms. Lone electron pairs are not shown. Each line is a bond, ex CO2 is O=C=O and H2O is H-O-H

Question 4

What does VSEPR stand for?

Answer 4

Valence Shell Electron Pair Repulsion

Question 5

What is VSEPR theory?

Answer 5

Electron pairs in the valence shell of the central atom repel and must be as far apart from each other as possible. 3-dimensional models. Shown as steriodiagrams: Solid line = in plane of paper, dotted line (wifi looking thing) = directed into paper, wedge = bond directed out of paper.

Question 6

Two elements bonded together or a Central atom with two bonded elements and no lone pairs. Shape?

Answer 6

Linear

Question 7

Central atom with three bonded elements and no lone pairs. Shape?

Answer 7

Trigonal Planar

Question 8

A central atom with 4 bonded elements and no lone pairs. Shape?

Answer 8

Tetrahedral

Question 9

A central atom with 3 bonded elements and one lone pair. Shape?

Answer 9

Trigonal pyramidal.

Question 10

A central atom with two bonded elements and two lone pairs of electrons. Shape?

Answer 10

Bent

Question 11

What type of molecules are non-polar?

Answer 11

Diatomic and symmetrical molecules.

Question 12

How are charges represented when showing an atom diagram?

Answer 12

Using the greek letter delta ( 𝛿) (letter, NOT SYMBOL), followed by a + or -.

Alternatively, an arrow with the tip pointed towards the negative end, and a small perpendicular line at the negative end (like -+—>_

Question 13

How to determine if a molecule is polar or non-polar using shape?

Answer 13

If there are any lone pairs of electrons or the ligands are different, the molecule is polar. (Non-symmetrical)

If there are no lone pairs and all ligands are the same, the molecule is non-polar. (Symmetrical).

Question 14

What is a ligand?

Answer 14

An atom bonded to a central atom.

Question 15

What are intramolecular forces?

Answer 15

Forces within an atom. There are ionic, covalent, and metalic bonds.

Question 16

Of the three types of intramolecular forces, which is the strongest and weakest?

Answer 16

Ionic is the strongest. covalent is the next strongest. Metallic is the weakest.

Question 17

Are intramolecular bonds or intermolecular bonds stronger?

Answer 17

Intermolecular bonds are much weaker than intramolecular bonds.

Question 18

Are intermolecular forces stable? What about intramolecular forces?

Answer 18

Intermolecular forces are not strong or stable. Intramolecular forces are very strong and stable.

Question 19

What kinds of intermolecular forces are there?

Answer 19

Van Der Waals Forces: London dispersion - Occur in non-polar molecules, caused by temporary shifts in electron density (caused by collisions. Dipole-Dipole forces - Between polar molecules, stronger than London dispersion. Neighbouring polar molecules align themselves so that the oppositely charged regions line up.

Hydrogen bonds. The strongest of all the intermolecular forces. Occur when hydrogen is bonded to a small, highly electronegative element like fluorine, oxygen, or nitrogen to produce a polar molecule. The hydrogen atom doesn’t hold its electron often, exposing the proton creating a very powerful positive charge (compared to the negative side).

Question 20

How can you tell what kind of intermolecular bond is active?

Answer 20

Non-polar: London dispersion.

Polar and no-hydrogen/weak electronegativity in bonded element: Dipole-dipole.

Hydrogen and very electronegative element: Hydrogen bond.

Question 21

Ionic bond definition.

Answer 21

Attraction between positive and negative ions.

Question 22

Covalent bond definition.

Answer 22

Attraction where electrons are shared.

Question 23

Electronegativity definition.

Answer 23

Measure of attraction for electrons.

Question 24

Polar covalent bond definition.

Answer 24

Unequal sharing of electrons.

Question 25

Nonpolar covalent bond definition.

Answer 25

Equal sharing of electrons.

Question 26

Metallic bond definition.

Answer 26

Attraction between positive ions and electrons.

Question 27

Dipole-dipole attraction definition.

Answer 27

Attraction between polar molecules.

Question 28

London dispersion forces definition.

Answer 28

Only attraction between non-polar molecules.

Question 29

Bonding electron definition.

Answer 29

Single, unpaired, valence electron.

Question 30

Lone pair electrons

Answer 30

Paired valence electrons.

Question 31

Difference between ionic and molecular compounds at room temperature.

Answer 31

Ionic compounds are solid at room temperature because they have many strong bonds.

Molecular compounds are usually gas and liquid at room temperature because they have fewer bonds that are weaker.

Question 32

How conductive are ionic compounds?

Answer 32

Not conductive when solid. Their ions cannot move preventing conduction, unless they are a gas or liquid.

Question 33

How conductive are molecular compounds?

Answer 33

They cannot conduct in any state because they have no free ions.

Question 34

How do ionic and molecular compounds differ in solubility?

Answer 34

Ionic compounds often dissolve in water because water can often strip away ions. Molecular compounds do not share this quality.

Question 35

How do ionic and molecular compounds differ in physical strength?

Answer 35

Ionic compounds are very hard, but brittle.

Molecular compounds are softer and more malleable.

Question 36

Describe the current quantum theory of the atom.

Answer 36

Protons and neutrons form an incredibly dense and small nucleus surrounded by clouds of electrons. These electrons occupy orbitals of different shapes and energy levels. These orbitals can only hold 2 electrons (Pauli Exclusion Principle) and are always filled with one electron before taking a second electron (Hund’s rule).

Question 37

Electronegativity difference and their polarity

Answer 37

0-0.4 non polar covalent bond
0.4-1.6 polar covalent bond
> 1.7 ionic bond

Question 38

What makes something a hydrogen bond?

Answer 38

Hydrogen containing POLAR molecule. (exception of some metal hydrides).
Otherwise London dispersion.

Question 39

What are the parts of a steriodiagram?

Answer 39

Central atom and ligands (circled)

Straight lines go across paper, wedges come up from paper, wifi lines go into paper

Question 40

Two types of acids

Answer 40

Oxy acids have three or more elements

Binary acids have two elements

Question 41

What scale is electronegativity on?

Answer 41

Pauli scale

Question 42

Lewis dot equation, how do you format?

Answer 42

Metal with dots + non-metal with dots and brackets around => result

Don’t forget to add brackets whenever there is more than 1 atom of an element