Lecture 1

Question 1

What is an atom?

Answer 1

An atom is the smallest unit of matter that retains the chemical properties of an element.

Question 2

What is an element?

Answer 2

An element is a pure substance made up of only one type of atom and cannot be broken down by physical or chemical means.

Question 3

What is a compound?

Answer 3

A compound is a pure substance composed of two or more elements that are chemically combined.

Question 4

What is a molecule?

Answer 4

A molecule is two or more atoms chemically bonded together, which can be the same or different types of atoms.

Question 5

Know what each represents chemically.

Answer 5

Atoms make up elements, molecules are bonded atoms, and compounds are molecules with different elements.

Question 6

What are the subatomic particles?

Answer 6

Protons (positive, nucleus, 1 amu), Neutrons (neutral, nucleus, 1 amu), Electrons (negative, orbitals, negligible mass).

Question 7

Which subatomic particle participates in chemical bonding?

Answer 7

Electrons, specifically valence electrons, participate in chemical bonding to achieve an octet.

Question 8

Where are electrons usually found in an atom?

Answer 8

Electrons are arranged in electron shells or energy levels (think of different floors in a mall). Within those shells electrons occupy specific orbitals (s, p, d, f) which are like stores or rooms on each floor where electrons are most likely to be found

Question 9

What are valence electrons?

Answer 9

Valence electrons are the electrons that occupy the outermost shell.

Question 10

What is an octet?

Answer 10

An octet is when an atom reaches stability with a full outer shell of 8 electrons, with exceptions like hydrogen.

Question 11

Be able to use the concept of an octet to determine the number of electrons needed for bonding.

Answer 11

1. Determine the number of electrons in the atom (atomic number). 2. Fill shells based on 2(n)^2 rule.

Question 12

What is the difference between an ionic bond and a covalent bond?

Answer 12

Ionic bonds involve electron transfer (metal + nonmetal), covalent bonds involve electron sharing (nonmetals).

Question 13

How are covalent bonds represented in a Lewis dot structure?

Answer 13

Covalent bonds are represented as single (–), double (=), or triple (≡) straight lines.

Question 14

How are lone pairs of electrons represented in a Lewis dot structure?

Answer 14

Lone pairs are represented as dots around an atom, showing non-bonded electrons.

Question 15

How many electrons are in a single bond?

Answer 15

2 electrons (1 shared pair).

Question 16

How many electrons are in a double bond?

Answer 16

4 electrons (2 shared pairs).

Question 17

How many electrons are in a triple bond?

Answer 17

6 electrons (3 shared pairs).

Question 18

How can one determine if a covalent bond is polar or nonpolar?

Answer 18

By checking electronegativity differences: polar bonds have partial charges, nonpolar bonds share electrons equally.

Question 19

Know the various symbols used to determine a dipole.

Answer 19

Dipole symbols: δ+ (partial positive), δ- (partial negative), and an arrow pointing to the more electronegative element.

Question 20

How are electrons distributed in a nonpolar vs. polar covalent bond?

Answer 20

Polar: Unequal sharing, dipole formed. Nonpolar: Equal sharing, no dipole.

Question 21

What are bonding vs. nonbonding (intermolecular) forces?

Answer 21

Bonding forces occur within molecules (strong), nonbonding forces occur between molecules (weaker).

Question 22

What are the three types of intermolecular forces?

Answer 22

Hydrogen bonding, dipole-dipole interactions, and London dispersion forces.

Question 23

What are the conditions for London dispersion forces?

Answer 23

They occur in all molecules but dominate in nonpolar ones; stronger in larger molecules with more electrons. London dispersion forces happen due to random electron movement. When two molecules are next to each other, one molecule randomly develops a temporary dipole due to the movement of electrons. Thid temporary dipole induces a dipole in their neighboring molecule. These molecule are then weakly attracted to each other because of these temporary charges.

Question 24

What are the conditions for dipole-dipole forces?

Answer 24

Dipole-dipole interactions occur between polar molecules with permanent partial charges.

Question 25

What are the conditions for hydrogen bonding?

Answer 25

An H atom must be covalently bonded to N, O, or F in one molecule and interact with a lone pair on another N, O, or F in a different molecule.

Question 26

How do you identify an H-bond donor vs. acceptor?

Answer 26

The molecule supplying H is the donor; the molecule with the lone pair is the acceptor.

Question 27

Do all polar molecules participate in hydrogen bonding?

Answer 27

No, only molecules where H is bonded to N, O, or F can hydrogen bond.

Question 28

Can nonpolar molecules mix with water?

Answer 28

No, because water is polar and nonpolar molecules are hydrophobic, causing them to separate.

Question 29

Why is water polar and not linear?

Answer 29

Water has an unequal sharing of electrons, creating dipole interactions; a linear shape would cancel out charges.

Question 30

Why can’t dimethyl ether molecules hydrogen bond?

Answer 30

They lack N, O, or F with a lone pair of electrons.

Question 31

How do two molecules of dimethyl ether interact?

Answer 31

Dipole-dipole interactions.

Question 32

Why are lone pairs important?

Answer 32

They impact molecular shape, polarity, and interactions. Atoms with lone pairs are often polar and can participate in hydrogen bonding.

Question 33

Why don’t nonpolar molecules dissolve in water?

Answer 33

Water forms strong hydrogen bonds with itself and cannot form strong interactions with nonpolar molecules, causing them to be excluded.

Question 34

If London dispersion forces are weak, why don’t nonpolar molecules dissolve in water?

Answer 34

Dissolving requires breaking old forces and forming strong new ones. Water cannot form strong enough bonds with nonpolar molecules.

Question 35

What happens when a nonpolar molecule enters water?

Answer 35

Water molecules rearrange themselves to form a 'cage' around the nonpolar molecule, leading to phase separation (hydrophobic effect).