Week 1

Question 1

Proton

Answer 1

Positive charge, located in nucleus, contribute significantly to mass of atom

Question 2

Neutron

Answer 2

Neutral charge, found in nucleus, contributes significantly to mass of atom

Question 3

Electron

Answer 3

Negative charge, occupies regions of space called orbitals (exact location unpredictable), have much smaller mass and contribute negligibly

Question 4

Graph: distance between two atoms and potential energy

Answer 4

1. Atoms are far apart. PE approaches 0. 2 atoms are independent
2. Atoms are close together. There is some attraction. Potential energy decreases.
3. Atoms are at the observed bond distance when they form a molecule (Most stable configuration. The bond is strongest)
4. The atoms are extremely close and there are strong repulsive forces. Increase in PE.

Question 5

What is means for an atom to be partially charged.

Answer 5

Atom has partial electric charge because the electrons are not shared equally. Electronegativity measures how strongly an atom attracts electrons in a chemical bond, where a more electronegative atom attracts shared electrons more strongly, resulting in a partial negative charge on it and a partial positive on the atom attracting the electrons less. Water molecules have polar covalent ponds because oxygen is more electronegative than hydrogen.

Question 6

Nonpolar covalent bond

Answer 6

Forms when electrons are shared equally between atoms, resulting in no partial charges

Question 7

Polar covalent

Answer 7

Electrons shared unequally between 2 atoms, lending to partial positive charge on one atom and partial negative on another

Question 8

Ionic bond

Answer 8

One atom completely transfers an electron to another, resulting in the formation or positively and negatively charged ions that attract each other. This happens when there is a large difference in electronegativity between the two atoms

Question 9

Hydrogen bond

Answer 9

Hydrogen atom covalently bonded to a highly electronegative atom (like O or N) is attracted to another electronegative atom

Question 10

Van deer Waals forces

Answer 10

Weak interactions that arise from transient dipoles in molecules

Question 11

Hydrophilic and hydrophobic

Answer 11

Hydrophilic substance can dissolve or form hydrogen bonds with water due to its polarity
Hydrophobic substance does not mix well with water. It is no polar and lacks the charged regions necessary for interacting with polar water molecules

Question 12

Elements

Answer 12

Pure substances made up of single type of atom, organized based on chemical properties

Question 13

Atoms

Answer 13

basic building blocks of matter, and they consist of three types of subatomic particles:
◦ Protons (positively charged particles)
◦ Neutrons (neutral particles)
◦ Electrons (negatively charged particles).
• The nucleus of an atom contains the protons and neutrons, while the electrons move around the nucleus in specific regions of space known as orbitals.

Question 14

Atomic number

Answer 14

Number of protons in an atom. Defines the element

Question 15

Atomic mass

Answer 15

Sum of protons and neutrons. Protons and neutrons each have mass of 1

Question 16

Isotopes

Answer 16

Variations of an element where atoms have the same number of protons but different numbers of neutrons (difference in atomic mass)

Question 17

Ions

Answer 17

Atoms that gain or lose electrons in chemical reactions
◦ Cations are positively charged ions formed when an atom loses one or more electrons.
◦ Anions are negatively charged ions formed when an atom gains one or more electrons.

Question 18

Electron orbitals and energy levels

Answer 18

Electrons are not positioned in fixed orbits around the nucleus but in orbitals, which define where an electron is likely to be found. They come in different shapes/sizes
• Each orbital corresponds to a specific energy level (or shell). The closer the orbital is to the nucleus, the lower the energy of the electron.
◦ First shell (n=1): Can hold a maximum of 2 electrons, occupying one spherical orbital.
◦ Second shell (n=2): Can hold up to 8 electrons and consists of a combination of spherical and dumbbell-shaped orbitals.
◦ Electrons fill the orbitals closest to the nucleus first, as these have lower energy. As the number of electrons increases, additional shells are filled.

Question 19

Periodic Table

Answer 19

Tabular arrangement of elements based on increasing atomic number
◦ Rows (Periods): same period=same number of electron shells (energy levels).
◦ Columns (Groups): same group=same number of electrons in their outermost electron shell (valence electrons)

Question 20

Covalent bond

Answer 20

Most common bond in biological molecules. Outermost orbitals of two atoms overlap as they approach each other and each atom shares one electron to form a pair of electrons. Atoms tend to form covalent bonds so that their outer shell of electrons is filled (OCTET RULE)

Question 21

Water

Answer 21

polar molecule due to the unequal distribution of electrons. O is more electronegative than H, causing a slight negative charge on the O atom and slight positive charges on the H atoms.
Water molecules form H-bonds between the slight positive Hs and the negative Os of adjacent water molecules. These are WEAK BONDS (weaker than covalent), but give water unique properties

Question 22

Properties of Water

Answer 22

Density of Water: transient H-bonds in liquid water, allowing the molecules to remain relatively close. (Ice floats)
Cohesion+ Surface Tension: the tendency for water molecules to stick to each other—>high surface tension
Heat Capacity/Temperature Regulation: resists changes in temperature. When heated, much of added energy goes into breaking H-bonds rather than increasing the kinetic energy of molecules—>high specific heat capacity, which means it can absorb or release large amounts of heat without significantly changing temperature.

Question 23

pH

Answer 23

Measure of concentration of protons in a solution. Ranges from 0-14 (7 is neutral- Concentrations of H+ and OH- are equals)

Question 24

Amphipathic

Answer 24

Molecules with polar and nonpolar regions

Question 25

How many covalent bonds can an element form?

Answer 25

H- 1, C- 4, N- 3, O- 2

Question 26

Most abundant atoms

Answer 26

H, C, O, N

Question 27

Goals

Answer 27

• Describe the structure of an atom. • Define and relate the terms electronegativity and polarity. • Explain how nonpolar and polar covalent bonds are formed between atoms. • Explain how the potential energy of two atoms changes as they form or break a bond. • Describe each type of atomic bond and intermolecular force: nonpolar covalent bonds, polar covalent bonds, ionic bonds, hydrogen bonds, and van der Waals’ forces. • Define the terms hydrophilic and hydrophobic. By the time you take the first assessment of learning you should also be able to: • Identify the number of covalent bonds formed by H, C, O, and N. • Compare and contrast the relative electronegativities of H, C, O, and N. • Determine whether a molecule is likely to be polar or nonpolar based on its chemical structure and the relative electronegativity of its atoms. • Relate the potential energy change of an atomic interaction to its “strength”. • Compare the relative strengths of bonds and electrostatic interactions and relate these strengths to the amount of energy required to break them. • Determine whether a molecule is able to participate in hydrogen bonding with itself or another molecule based on its chemical structure and relative electronegativity of its atoms. • Determine whether a molecule is likely to be hydrophilic or hydrophobic based on its ability to form hydrogen bonds with water.