valence electrons
What are valence electrons?
Electrons in the outermost shell of an atom.
What do dots in a Lewis structure represent?
Valence electrons.
Name the three main phases of matter
Solid, liquid, gas.
What makes a bond polar?
Unequal sharing of electrons.
What kind of bond holds water molecules together?
Hydrogen bonds.
How many valence electrons does oxygen have?
6
What is shown inside brackets in an ionic Lewis structure?
The ions after electrons are transferred
What happens to molecules when a solid melts?
They gain energy and move farther apart.
What atom in water attracts electrons more strongly?
Oxygen.
Why does ice float on water?
Ice is less dense because water molecules form open hexagonal structures when frozen.
Why are valence electrons important?
They determine how an atom bonds with others.
What kind of bond forms when electrons are shared?
Covalent bond.
What happens to the motion of molecules as temperature increases?
They move faster.
What is a hydrogen bond?
Weak attraction between a hydrogen atom and an oxygen (or nitrogen) in another molecule.
Why is water called the “universal solvent”?
It dissolves many substances due to its polarity.
What happens to valence electrons in ionic bonding?
They are transferred from one atom to another.
Draw or describe the Lewis structure for water (H₂O).
Oxygen in center, two pairs of shared electrons with H, two lone pairs on O.
What is condensation?
Gas changing into a liquid.
Why is carbon dioxide nonpolar even though it has polar bonds?
Its shape is symmetrical, so charges cancel.
What happens to water molecules when they freeze?
They form a fixed, open lattice.
How can you find the number of valence electrons on the periodic table?
By the group (column) number for main-group element
What rule states that atoms are most stable with 8 valence electrons?
The octet rule.
What phase has particles vibrating in fixed positions?
Solid.
What determines if a molecule is polar overall?
The shape of the molecule and distribution of charge.
Why is it important that ice floats?
It insulates water below, allowing aquatic life to survive in winter.