Biology 1 - Lecture 3: Atomic Structure and Chemical Bonds

Flashcards covering atomic structure, chemical bonding, isotopes, periodic table basics, and the properties of acids and bases from Lecture 3.

Atom

A structure consisting of a nucleus containing protons and neutrons, surrounded by electrons that are attracted to the nucleus by their negative charge.

Element

A substance composed of only one type of atom.

Dalton (Da)

A unit of mass used for subatomic particles, where $1\,Da \approx 1.7 \times 10^{-27}\,kg$ and an electron's mass is approximately $0.0005\,Da$.

Atomic Number ($Z$)

The number of protons in an atom's nucleus, which determines the type of element.

Mass Number ($A$)

The sum of the number of protons and neutrons in an atom's nucleus.

Isotopes

Atoms of the same element that differ in their number of neutrons.

Radioactive Decay

A process in which an unstable isotope emits energy and particles (such as $\alpha$ or $\beta$) to transform into a different element.

Orbitals

Regions in space that represent the probability of finding an electron in a specific location.

Valence electrons

The electrons in the outermost shell of an atom that determine its chemical properties and reactivity.

Octet Rule

The tendency of atoms to gain, lose, or share electrons in order to have eight electrons in their outermost valence shell.

Molecule

The smallest unit of a compound that retains its properties, formed when two or more atoms create chemical bonds.

Covalent bond

A chemical bond characterized by the sharing of one or more pairs of valence electrons between atoms.

Electronegativity

A measure of the relative ability of an atom to attract electrons within a covalent bond.

Non-polar covalent bond

A type of bond formed between atoms with similar electronegativity, resulting in an even distribution of electrons.

Polar covalent bond

A bond where electrons are pulled closer to the more electronegative atom, creating partial charges ($\delta+$ and $\delta-$).

Hydrogen bond

A weak attraction between a partially positive hydrogen atom ($\delta+$) in one molecule and a partially negative atom ($\delta-$) in another molecule or different part of the same molecule.

Ionic bond

A bond formed through the complete transfer of electrons from one atom to another, resulting in electrostatic attraction between a positive ion and a negative ion.

Hydrophobic interaction

The interaction of nonpolar substances to stay together in the presence of polar substances like water.

Van der Waals interactions

Weak electrical interactions driven by induced charges when the outer electron clouds of two nearby atoms are very close.

Mole

A measurement of quantity containing approximately $6 \times 10^{23}$ particles.

Molar concentration ($M$)

A unit of concentration defined as the number of moles of a substance per liter of solution.

pH

A quantitative measure of a solution's acidity, calculated as $pH = -\log_{10}[H^+]$.

Acid

A substance that releases protons ($H^+$) when dissolved in water, resulting in a proton concentration higher than the hydroxide concentration ($[H^+] > [OH^-]$).

Base

A substance that accepts protons ($H^+$) when dissolved in water, resulting in a proton concentration lower than the hydroxide concentration ($[H^+] < [OH^-]$).

Hydronium ion ($H_3O^+$)

The ion formed when a free proton ($H^+$) binds to a water molecule in solution.