Bonding L7 Flashcards
The Octet Rule
- Elements tend to gain, lose, or share electrons to acquire a full octet
- In n=1 a full octet consists of 2 electrons and there is only one 1s orbital
- from n=2 to n=7, a full octet consists of 8 electrons. a full s-orbital and a full p-subshell
Ionic compounds formed from
- metal and nonmetal
- metals lose electrons
- non-metals gain electrons
- ions can form ionic compounds through electrostatic attractions
- crystal lattice structure
d-block element charges
1 to 4, usually 2
sn and pb can be
+2
d-block cations
- These elects lose electrons from their highest s-sublevel first before losing from their d-sublevel
Ionic Bonding
- Metals transfer electrons to non-metals, and the two form bonds due to the electrostatic attractions between them
- Cations (metal ions) and anions (non-metal ions) form electrostatic bonds based on opposite charges. (cations and anions may be polyatomic)
The forming of an ionic bond is an
exothermic process
Strength of an ionic bond
- very strong
- lots of energy to melt or vaporize these solids
- the melting/vaporizing is a very endothermic process in order to break the bond
symbols
- H=energy in chem, entropy
- + in front of energy indicates endothermic
Factors affecting melting points of ionic solids
- smaller radius=greater melting point
- higher charge= greater melting
- charge is more significant than melting point
Properties of Ionic Solids-
- Strong bonds
- Cleave along planes
- Solubility and Conductivity
Properties of Ionic Solids- Strong bonds
- Very strong Coulombic forces of attraction between cations and anions
- High melting points
- very hard
- low volatility (don’t evaporate easily)
- can’t smell ionic compounds because ions are tightly held
Properties of Ionic Solids- Solubility and Conductivity
- Most are soluble in polar solvents
- They conduct electricity only when molten or dissolved in a polar solvent, as the charged particles are free to move
- The higher the concentration of ions in a solution, the higher the electrical conductivity
- Electric current conducted through solution if there are ions present
- pure water can’t conduct electricity but when you get in water, ions in water and it can conduct electricity
- If solvent has enough particles its a polar substance
Covalent bonds
- one atom shares one or more pairs of electrons with another atom so that they both acquire full octets
- occurs between two non-metals
Electronegativity and Bond Polarity
- EN= elements ability to attract electrons in a chemical bond
- nonpolar= equal sharing of electrons
- Similar EN but not exact= polar covalent
- Ionic- big EN difference
What bonds look like
- Nonpolar covalent looks like a symmetrical circle since its equal sharing
- Polar covalent looks like an unsymmetrical circle with more electrons around more EN element
- Ionic there is no circle because electrons are transferred not shared
Polar covalent bonds
- The atom with the higher EN develops a partial negative charge as the valence electrons from both atoms spend more time around it
- The atom with the lower EN develops a partial positive charge, which is equal in magnitude to the partial negative charge of the more EN atom
- These partial charges increase as EN differences increase
- The sum of the particle charges in any molecule or ion is always equal to the overall charge on the species
EN charges of bond type
- 0-.5
ionic vs covalent basic difference
- ionic transfers electrons
- covalent share electrons
Molecular compounds defined
- two or more non-metals bonded together to form a compound
- bonds between atoms are nonpolar covalent or polar covalent
polyatomic ions defined
- A combination of non-metals or metals and non-metals bonded together to form a polyatomic ion
- Bonds between atoms are nonpolar covalent or polar covalent
Do metals gain or electrons in order to acquire a full octet
lose
What possible charges can lead acquire as an ion
+4, +2
What possible charges can iron acquire as an ion
+2, +3
are ionic solids malleable?
no, do not shape but have sharp edges. If you try and break into pieces
