Chemistry of Life - Chapter 2 Flashcards

Definition: Elements are the basic form of all matter.
Composition: They cannot be broken down into different components by chemical means.
Periodic Table: The periodic table lists all known elements, with $92$ occurring naturally in nature.

Major Elements (96%): All living things primarily consist of:
- Carbon (C)
- Oxygen (O)
- Nitrogen (N)
- Hydrogen (H)
Secondary Elements (4%): Humans also require:
- Calcium (Ca)
- Phosphorus (P)
- Potassium (K)
- Sulfur (S)
- Sodium (Na)
- Chlorine (Cl)
- Magnesium (Mg)
Trace Elements (0.01%): Essential in very small amounts:
- Iron (Fe)
- Iodine (I)
- Fluorine (F)

Element: Consists of only one type of atom.
Molecule: Formed when two or more atoms are joined together chemically.
- The atoms can be the same element (e.g., $O<em>2$ ) or different elements (e.g., $H</em>2O$ ).
- Relationship to Compounds: All compounds are molecules, but not all molecules are compounds.
Compound: Formed when two or more different elements are joined together chemically in a fixed proportion.
- Compounds take on different physical and/or chemical properties than their individual constituent elements.
- They are typically difficult to separate into their individual elements.
Mixture: A combination of two or more different molecules that are not chemically bonded.
- The substances in a mixture retain their individual properties.
- Mixtures can be separated using physical means, such as filtration, differences in density, or evaporation.

Definition: The smallest unit of an element that retains the chemical properties of that element.
Differentiation: Elements differ from one another based on the number of protons they contain.
Atomic Number: This number is unique to each element and is equal to the number of protons in an atom's nucleus.
Atomic Mass: Represents the average mass of an element's naturally occurring isotopes, typically measured in atomic mass units (amu).

Protons ( $P^+$ )
- Location: Found within the nucleus of an atom.
- Identity: The number of protons defines the element (e.g., all carbon atoms have $6$ protons).
- Atomic Number: The number of protons is equal to the atomic number.
- Charge: Positively charged ( $+1$ ).
- Role: Their positive charge holds the negatively charged electrons close to the nucleus.
Neutrons ( $N^0$ )
- Location: Also found within the nucleus.
- Number: The number of neutrons is calculated as the atomic mass (rounded to the nearest whole number for a specific isotope) minus the number of protons.
- Charge: Neutrally charged ( $0$ ).
- Role: Help to stabilize the nucleus, especially in larger atoms.
Electrons ( $E^-$ )
- Location: Orbit the nucleus in specific energy levels called orbitals or electron shells.
- Number: In a neutral atom, the number of electrons is equal to the number of protons.
- Charge: Negatively charged ( $-1$ ).
- Role: They are the basis of chemical reactions, as their arrangement and interactions determine how atoms bond.

Elements are typically represented by a symbol with associated numbers:
- Mass Number: Located at the top left, it is the total number of protons plus neutrons in a specific isotope ($ ext{e.g., Atomic # of Carbon = 6, Mass # = 12, means 6 protons + 6 neutrons}$).
- Atomic Number: Located at the bottom left, it is the number of protons ($ ext{e.g., Carbon has 6 protons, Oxygen has 8 protons}$).
- Atomic Mass (or Atomic Weight): Usually found below the element symbol, it's the average mass of all isotopes (e.g., Carbon's atomic mass is $12.011$ , Oxygen's is $15.999$ ).
Electron Shells/Orbitals:
- Electrons occupy distinct energy levels around the nucleus.
- The innermost shell holds a maximum of $2$ electrons.
- Subsequent shells (outer shells) attempt to achieve an octet, holding up to $8$ electrons for stability (e.g., Oxygen has $8$ total electrons, with $6$ in its outer shell).

Definition: Isotopes are varying forms of an element that have the same number of protons (and thus the same atomic number) but differ in the number of neutrons.
Chemical Behavior: Despite differing neutron counts, isotopes generally behave in a similar manner in chemical reactions because chemical reactions primarily involve electrons, which are the same in a neutral atom.
Stability: A difference in neutron number, especially a significant deviation from the most common isotope, can lead to instability of the element's nucleus.

Definition: A radioisotope is an isotope with an unstable nucleus due to an unfavorable proton-to-neutron ratio. This instability causes the atom to release energy waves and particles, known as radiation, as it decays to a more stable form. This process is called radioactive decay.

Basic Science Research:
- Goal: To develop targeting molecules (vehicles) to deliver medications or