Chemistry Notes for Pharmacists

Chemistry is defined as the science of matter, focusing on its composition, properties, behavior, and interactions.

Future pharmacists must learn chemistry.
- As independent prescribers, pharmacists need a strong understanding of chemistry to make informed decisions about medications and their effects.
- Chemistry is referred to as the 'central science' in pharmacy education, as it integrates knowledge from various scientific disciplines.

Matter: Anything that occupies space and has mass.
- Example: Matter can include solids, liquids, gases, and plasma.
Atoms: The basic building blocks of matter derived from the Greek word 'atomos' meaning 'uncuttable.'
- Structure of an Atom:
- Contains protons, neutrons, and electrons.
- Proton: Positive charge, located in the nucleus.
- Neutron: No charge, also in the nucleus.
- Electron: Negative charge, exists in cloud-like regions surrounding the nucleus.
Unit of Measurement: 1 atomic mass unit (amu).
Mass Comparison:
- Protons and neutrons have equal mass.
- Electrons have a negligible mass.

Most of an atom is empty space, with protons and neutrons densely packed in the nucleus and electrons forming surrounding clouds.
Charge of the Atom: The overall charge of an atom is neutral when the number of protons equals the number of electrons.

Atomic Number (Z): The number of protons in an atom, which defines the element.
**Different Elements:
- Identified by the unique number of protons (atomic number).
- Isotopes are variants of the same element with different neutron counts, leading to different atomic masses.

The atomic mass of an element is the weighted average of all its naturally occurring isotopes.
- Example: Chlorine has two stable isotopes: Chlorine-35 and Chlorine-37 with isotopic abundances affecting the average atomic mass (e.g., Chlorine has an atomic mass of 35.45 amu).

Arranged by increasing atomic number (number of protons).
Elements display periodicity, showing similar properties in groups (columns) of the table.
- Group 1: Alkali metals (e.g., Lithium, Sodium) typically lose one electron.
- Group 17: Halogens (e.g., Fluorine, Chlorine) typically gain electrons.

Isotopes differ in neutron count but maintain the same proton count (same element).
Example: Chlorine-35 has 17 protons and 18 neutrons, whereas Chlorine-37 has 17 protons and 20 neutrons.
The relative abundance of isotopes must be accounted for when calculating average atomic mass.

Electrons are organized into energy levels called shells, corresponding to the periodic table's rows.
Old Atomic Model vs. New Model:
- Old: Electrons orbit like planets.
- New: Electrons exist in probability clouds (orbitals) defined by quantum mechanics.
Quantum Numbers:
- Principal quantum number (n): indicates the energy level and size of the orbital.
- Angular momentum quantum number (l): determines the shape of the orbital (s, p, d, f).
- Magnetic quantum number (m_l): describes the orientation of the orbital in space.
- Spin quantum number (m_s): indicates the spin of the electron (±1/2).

Types of Orbitals:
- s Orbital: Spherical shape, can hold 2 electrons.
- p Orbital: Dumbbell shape, can hold 6 electrons across 3 orientations.
Filling Order:
- Follow the Aufbau principle to fill from the lowest energy level to higher.
- Use the Pauli exclusion principle for electron spins to avoid identical quantum numbers in the same orbital.
- Use Hund’s rule, which states electrons fill degenerate orbitals singly before pairing.

Valence electrons are the outermost electrons that determine an atom's chemical reactivity and bonding properties.
Core electrons are those that are not involved in bonding.

Covalent Bonds: Electrons are shared between atoms to complete valence shells.
Ionic Bonds: Electrons are transferred from one atom to another, forming charged ions (cations and anions).

Atoms strive to achieve a full outer shell of electrons akin to noble gas configurations for stability.
Example: Fluorine, needing one more electron to complete its outer shell, gains an electron to become F⁻.

Atoms achieve stability through chemical bonds (ionic or covalent) by gaining, losing, or sharing electrons.
Understanding these principles and electron configurations is crucial for predicting molecular behavior in pharmacy and chemistry.

These foundational concepts in chemistry are integral for students pursuing careers in pharmacy and other sciences, providing essential knowledge for understanding drug mechanisms and interactions.