Chapter 4: Bonding and Phases Flashcards
Coulomb’s Law
All bonds occur because electrostatic attractions. Atoms stick together to form moleucles, and atoms and molecules stick together to form liquids/solids because electrons of one atom are attracted to the postively charged nucleus of another atom.
Coulomb’s Law (equation)
Attractive force is proportional to (+q)(-q)/r2
+q = magnitude of the positive charge
-q = magnitude of the negative charge
r = distance between the charges
What things should be able to extrapolate from Coulomb’s Law (formula)?
- Bigger charges means stronger bonds; smaller charges mean weaker bonds
- Charges close together mean stronger bonds; charges far apart mean weaker bonds
Why atoms join to form molecules?
Because atoms like to have a full outer shell of electrons. This usually means having eight electrons in the outer shell.
What will atoms with too many or too few electrosn in their valence shells do?
Find one another and pass the electrons around until all the atoms in the molecule have stable outer shells.
What are ionic bonds?
An ionic solid is held together by an electrostatic attractions between ions that are next to one another in a latitice structure. They often occur between metals and nonmetals. In an _______, electrons are not shared, Instead, one atom gives up electrons and becomes a postively charged ion while the other atom accepts electrons and becomes a negatively charged ion.
Two ions in an ionic bond are held together by what?
Electrostatic forces.
Describe a molecule of NaCl and a crystal of NaCl.
A sodium atom gives up its ingle valence electron to a chlorine atom, which has seven valence electrons and uses the electron to complete its outer shell (with eight). The two atoms are then held togetherby the positive and negative charges on the ions.
The same electrostatic attractions that hold together the ions in a molecule of NaCl hold together a crystal of NaCl. So no real distinction between the molecules and the solid.
Ionic bonds are strong, and substances held together by ionic bonds have high melting and boiling points.
What does Coulomb’s law state about ions?
The more highly charged ions will form stronger bonds than less highly charged ions and smaller ions will former stronger bonds than larger ions. So an ionic bond composed of ions with +2 and -2 charges will be stronger than a bond composed of ions with +1 and -1 charges. Also, the smaller the ions in an ionic bond, the stronger the bond. This is because ta small ionic radius allows the charges to get closer together and increases he forces between them.
What’s in an ionic solid?
Each electron is localized around a particular atom, so electrons do not move around the lattice; this makes ionic solids poor conductors of electricity. Ionic liquids, hover, do not conduct electricity beacause the ions themselves are free to move about in the liquid phase, although the electrons are still localized around particular atoms.
Salts are held together by what bonds?
Ionic bonds
What are covalent bonds?
Two atoms share electrons. Each atom counts the shared electrons as part of its valence shell. In this way, both atoms achieve complete outer shells.
