Atomic Structure and Bonding

Atomic Structure and Bonding

• Atoms: Single units of an element.
• Molecules: Two or more atoms of the same type bonded together.
• Compounds: Two or more atoms of different types bonded together.
• Types of Bonding:
  • Ionic bonding: Electrons are lost from one atom and gained by another. Metals lose electrons, becoming positively charged ions (cations). Nonmetals gain electrons, becoming negatively charged ions (anions). This electrostatic attraction holds the ions together.
  • Covalent bonding: Electrons are shared between atoms. Atoms can share one pair (single bond), two pairs (double bond), or three pairs (triple bond) of electrons.

Properties and Behavior of Atoms

• Valence electrons: Electrons in the outermost energy level of an atom. These electrons are involved in bonding.
• Electron shells/orbitals: The regions surrounding the nucleus where electrons are found. Atoms strive to gain, lose or share valence electrons to fill their valence shell and achieve stability. This is the driving force of elements undergoing chemical reactions.
• Ionic bonding: Occurs between a metal and a nonmetal.

Periodic Table Organization

• Organizing elements: Elements organized by increasing atomic number and periodic trends in properties.
• Groups/columns: Elements in the same column have similar chemical properties.
• Periods/rows: Elements in the same row have increasing numbers of electron shells.
• Categories: Metals, nonmetals, and metalloids. Metalloids have properties that are intermediate between metals and nonmetals.

Atomic Structure

• Atomic number: Number of protons in the nucleus of an atom.
• Atomic mass: Number of protons and neutrons in the nucleus (approximately).
• Identifying particles: Protons (positive charge), neutrons (no charge), and electrons (negative charge).

Determining Atomic Number, Mass, and Particles

• Determining proton number: The atomic number represents the number of protons.
• Calculating neutrons: Subtract the atomic number from the atomic mass to find the number of neutrons.
• Determining electron number: In a neutral atom, the number of electrons is equal to the number of protons.