02 Atomic Bonding and Crystal Structures Free Online FlashCards

What holds ions together in an ionic solid?

Ionic bonding is the electrostatic attraction between oppositely charged ions. Ionic solids form extended, electrically neutral lattices.

What is a unit cell?

A unit cell is a volume that repeats by translation to build a crystal.

How many atoms are in a BCC conventional cell?

A BCC conventional cell contains 2 atoms: its 8 corner atoms contribute 1 atom in total, and its interior atom contributes 1.

What do [uvw] and <uvw> denote?

Square brackets, such as [uvw], denote one crystallographic direction; angle brackets, such as <uvw>, denote a family of symmetry-equivalent directions.

What is the coordination in the rock-salt structure?

In the rock-salt structure, each ion has 6 nearest neighbors of opposite charge; its coordination is 6:6.

What makes covalent bonds directional?

Covalent bonds share electrons between particular atoms and are directional. In network solids, they extend throughout the crystal.

How does metallic bonding help explain metals’ conductivity?

Metallic bonding attracts positive atomic cores to delocalized valence electrons. Mobile electrons help metals conduct electricity and heat.

Where can secondary interactions be important?

Secondary interactions, such as van der Waals forces and hydrogen bonding, can act between molecules, polymer chains, or material layers.

How many atoms are in an FCC conventional cell?

An FCC conventional cell contains 4 atoms: its 8 corners contribute 1 atom in total, and its 6 face-centered atoms contribute 3.

What are the coordination numbers of BCC and FCC?

Coordination number is the number of an atom’s nearest neighbors. BCC has coordination number 8; FCC has 12.

What do (hkl) and {hkl} denote?

Parentheses, such as (hkl), denote one plane orientation; braces, such as {hkl}, denote a family of symmetry-equivalent planes.

What Miller index corresponds to a plane parallel to an axis?

A plane parallel to an axis has an intercept at infinity, so its Miller index for that axis is 0.