Chapter 2: The Chemical Context of Life

Question 1

What are atoms?

Answer 1

are the smallest unit of matter/ make up living and non living matter

Question 2

What does all matter consist of?

Answer 2

all matter consists of at least 1 chemical element

Question 3

What is a chemical element?

Answer 3

a pure substance made up of only one type of atom.

Question 4

List/give the organizational hierarchy of atoms, elements, and matter? What do atoms make up in terms matter?

Answer 4

atom>chemical element>matter
Atoms make up living/nonliving matter

Question 5

Of all the elements of life, how many are actually found in living organisms? And what are they?

Answer 5

majority of the elements are not utilized by living organisms. 97% of the mass of most life is composed of Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and sulfur (HNOPS) A.K.A bulk elements

Question 6

What are trace elements?

Answer 6

elements required for life and found in living organisms in very small amounts.

Question 7

Give 5 examples of trace elements?

Answer 7

NA
Ca
Cr
CI
Sn

Question 8

What defines an element? and what causes it to change?

Answer 8

an element is defined by its atomic number. adding a proton changes an element but adding any other subatomic particles doesn’t

Question 9

What is the mass number and the formula for calculating it?

Answer 9

is the mass of the nucleus of an atom.
Mass #= P+N

Question 10

What is an atomic mass or weight?

Answer 10

refers to the average total mass of all atoms of an element

Question 11

What are electron orbitals? and how can they be envisioned?

Answer 11

3d regions around the nucleus of an atom where electrons can be found. (can be envisioned in 2D as energy shells)

Question 12

What is the relationship of the energy of energy shells and their distance to the nucleus?

Answer 12

energy shells closer to the nucleus are lower in energy than distant shells.
Distant shells are typically higher in energy, more reactive, and the ones that form chemical bond

Question 13

What are valence electrons?

Answer 13

electrons found in the outermost shell energy shell (valence shell)

Question 14

What is a neutral net charge?

Answer 14

when the # of Ps balances out with the # of Es

Question 15

What is the octet rule?

Answer 15

states that atoms are stable (less reactive) when their valence shells are fully occupied.

Question 16

How many electrons can a each shell hold?

Answer 16

1st energy shell: a max of 2 electrons
2nd: a max of 8 electrons
shells beyond that: varying #

Question 17

What is an isotope?

Answer 17

are atoms of the same element that only vary in the # of neutrons.

Question 18

What does an isotope have in terms of atomic number and mass number?

Answer 18

the same atomic number, but different mass numbers

Question 19

What is atomic mass?

Answer 19

overall mass of an atom taking into account isotopes, which are very small and not expressed as an integer.

Question 20

What are isotopes?

Answer 20

different forms of the same element with the same P but different N

Question 21

How many isotopes are present in Carbon 12 (natural carbon)? and which is the most abundant?

Answer 21

There are 3 isotopes in carbon 12 with carbon 12 itself is 99% of carbon isotopes where the number of P and N are similar.

Question 22

What is true about carbon 13 and 14?

Answer 22

carbon 13 and 14 have the same number of protons but a different # of neutrons.

Question 23

Why is carbon 12 considered an isotope even though it has the same # of protons and neutrons?

Answer 23

isotopes are defined based on their differences in neutrons relative to the same element, not necessarily number of neutrons compared to protons.

Question 24

Explain the concept of Isotope (Carbon 12)?

Answer 24

concept of isotopes doesn’t require the # of neutron/protons to be different, it only requires the # of neutrons to vary while the same number of protons stay constant. It is not unique in being an isotope as they are defined y the variability of neutrons, not the quantity of protons/neutrons.

Question 25

What are radioactive isotopes?

Answer 25

unstable isotopes that break down and emit energy in the form of rays or particles.

Question 26

What is a half-life?

Answer 26

the time it takes for half of the radioactive atoms in a sample to break down at a pretty consistent rate.

Question 27

What determines the stability of an atom?

Answer 27

While the # of N play a role in determining whether an isotope is radioactive or not, it is the overall balance of N and P that determines the stability of an atom.

Question 28

What happens to energy during in a radioactive atom, and what is the purpose?

Answer 28

in a radioactive atom, energy and subatomic particles are released to reach a more stable state by emitting radiation.

Question 29

List the stability of Carbon and its isotopes?

Answer 29

Carbon 12 and 13= stable
Carbon 14= unstable because it has an unstable nucleus with too many neutrons compared to its protons,

Question 30

What causes stability to an atom?

Answer 30

equal or relatively similar # of protons and neutrons

Question 31

What are chemical bonds?

Answer 31

attractive forces between atoms, holding them together to form molecules and compounds.

Question 32

Define the following:
1. Molecules:
2. Compounds:

Answer 32

1. substance containing 2 or more chemically bound atoms (atoms can be of same or different element)
2. a complicated molecule of 2 different elements(atoms of different elements bonded together, and must consist of different elements)

Question 33

What is rule of saying regarding molecules and compounds?

Answer 33

all compounds are molecules but not all molecules are compounds

Question 34

What does a chemical formula reveal?

Answer 34

reveals the # and type of atoms in a molecule and help simplify structures

Question 35

Define the following terms:
1. Intermolecular bonds:
2. Intramolecular Bonds:

Answer 35

1. interactions between atoms of DIFFERENT molecules
2. interactions between atoms of the same molecule

Question 36

Are all molecules going to be classified as either intra or intermolecular?

Answer 36

no, because these terms specifically refer to the forces/ interactions happening rather than the molecule itself. Examples of these forces include ionic, covalent bonds, etc.

Question 37

What are covalent bonds?

Answer 37

an interaction between 2 atoms resulting from the equal sharing of electrons

Question 38

What are the two types of covalent bonds and why do these exist?

Answer 38

the two types of covalent bonds are polar and non-polar and they exist due to differences in the atom’s electronegativity.

Question 39

What is electronegativity?

Answer 39

it is a measure of an atom’s attraction to electrons or how hard these atoms pull on electrons. (measure on a scale of 0-4)

Question 40

What is the range of electronegativity on the periodic table?

Answer 40

It starts from low with hydrogen and increases in electronegativity as you reach oxygen which is one of the most electronegative elements

Question 41

What are non-polar covalent bonds?

Answer 41

have an equal sharing of electrons between atoms due to their relatively similar electronegativities. There is an equal force being applied to each side and therefore ends up in a nonpolar covalent bond

Question 42

What causes non- polar covalent bonds?

Answer 42

atoms of equal or similar electronegativities

Question 43

What are polar covalent bonds?

Answer 43

unequal sharing of electrons between atoms (due to different electronegativities) which leads to unequal distribution of electrons between atoms resulting in partial charges. (δ)

Question 44

What is a partial charge when it comes to polar covalent bonds?

Answer 44

because the electrons spend more time closer to one atom, that atom gains a partial negative charge (denoted as δ-). Conversely, the other atom, having electrons pulled away from it, gains a partial positive charge (denoted as δ+).

Question 45

What are Non-covalent bonds and what are some examples?

Answer 45

interactions between 2 atoms resulting from full or partial charges. Examples include ionic, and hydrogen bonds

Question 46

Define the following:
Partial charge:
Full charge:

Answer 46

1. Occurs when electrons are not completely transferred but are shared unequally in a covalent bond. This results in a slight negative charge (δ-) on the more electronegative atom and a slight positive charge (δ+) on the less electronegative atom.

2.Refers to the complete gain or loss of electrons, resulting in ions. For example, Na+ has lost an electron to become positively charged, while Cl- has gained an electron to become negatively charged.

Question 47

What are ions?

Answer 47

are atoms or molecules with a net electrical charge that have either a positive or negative charge due to the gain or loss of electrons

Question 48

Define the following, and their charges?
Anions:
Cations:
Neutral:

Answer 48

1. are - charged ions resulting from a + of an electron.
2. • charged ions resulting from a - of an electron.
3. When the # of electrons= the # of protons.

Question 49

What are ionic bonds?

Answer 49

electrical attractions between oppostiely charged ions. involves the TRANSFER of Electrons which van fill the valence shells of both atoms and create charges.

Question 50

What does the difference in electronegativity cause for?

Answer 50

A big difference in electronegativity= transfer of electrons which causes ionic bonds
Small difference or equal= share electrons which causes a covalent bond.

Question 51

What are hydrogen bonds? and what are some of their qualities?

Answer 51

interactions between a highly electronegative atom (F, O, or N) and a hydrogen atom.
weak individually but can be very strong together.

Question 52

Are F, O, and N the only elements that participate in a Hydrogen bond?

Answer 52

no they are not the only ones, but they are the primary elements that particpate in creating an H Bond.