chapter 2 intro chemistry

Vocabulary flashcards covering core concepts from the lecture notes on the periodic table, electron configuration, bonding, electronegativity, and cell membrane properties.

Periodic table

A chart of all known elements arranged by increasing atomic number and grouped by similar chemical properties.

Major elements in the human body

Elements that make up about 99% of body mass; commonly emphasized include carbon, hydrogen, oxygen, nitrogen, calcium, phosphorus, potassium, sodium, chlorine, magnesium, and iron.

Valence shell

The outermost electron shell of an atom that determines its bonding behavior.

Electron shell rule (2, 8)

In the simplified model, the first shell holds up to 2 electrons; each subsequent shell holds up to 8 electrons.

Noble gases

Elements with full outer electron shells that generally do not form bonds.

Carbon's electron configuration and bonding

Carbon has 6 electrons (2 in the first shell, 4 in the second) and can form up to four covalent bonds.

Sodium ion (Na+)

Sodium tends to lose one electron to form Na+, a positively charged ion.

Chlorine ion (Cl−)

Chlorine tends to gain one electron to form Cl−, a negatively charged ion.

Ionic bonding (NaCl)

Electrostatic attraction between oppositely charged ions, such as Na+ and Cl− in salt.

Electronegativity

An atom's ability to attract bonding electrons; increases across a period and up a group (toward the top-right of the table).

Polar covalent bond

A bond where electrons are shared unequally due to electronegativity differences, creating partial charges.

Nonpolar covalent bond

A bond where electrons are shared about equally; often occurs when electronegativity difference is small (e.g., C–H).

Amphipathic

A molecule with both polar (water-loving) and nonpolar (water-fearing) regions, such as phospholipids.

Phospholipid bilayer

Two-layer membrane with polar heads facing water and nonpolar tails inward; forms the cell membrane.

Cholesterol (in membranes)

A hydrophobic steroid that stabilizes membranes by fitting among phospholipids.

Glycolipids and glycoproteins

Membrane components with carbohydrate groups; contribute to protection and cell recognition.

Hydrogen bonds

Weak intermolecular bonds between a hydrogen atom bound to an electronegative atom (like O) and another electronegative atom; important for DNA stability and water properties.

Water polarity

Water is a polar molecule: oxygen is more electronegative (partial negative), hydrogens carry partial positive charges, enabling hydrogen bonding.

DNA hydrogen bonding

Hydrogen bonds between base pairs in the DNA double helix hold it together and allow separation during replication.

Dissociation in water (salts)

Ionic compounds dissociate into ions in aqueous solution (e.g., NaCl → Na+ + Cl−).

Atomic number

Number of protons in an atom's nucleus; determines the element's identity and position on the periodic table.

Element symbol

One- or two-letter abbreviation for an element (e.g., Na for sodium, Cl for chlorine).

Hydrophilic vs hydrophobic

Hydrophilic parts interact with water; hydrophobic parts avoid water.