Covalent Compounds Flashcards
Covalent Compounds
Form when 2 Nonmetal atoms share electrons in order to achieve a stable configuration (octet valence).
Covalent Bond
- When atoms share ve-
- Most try to achieve an octet (H is stable @ 2ve-)
- represented by a line (single, double, triple, etc)
Diatomic
Contains 2 atoms of the same element covalently bonded together.
Eg. H2, F2
Electron-dot Formulas of Covalent Compounds
Chemical symbols show side by side surrounded by ve- in Lewis-dot structure with bonds connecting the ve- to achieve the required octet for each atom.
of Covalent Bonds
Nonmetals generally form bonds equal to the number of ve- needed to acquire a stable configuration.
Exceptions to the Octet Rule
Octet rule is useful but there are exceptions.
Lone Pairs
- Paired ve- drawn in the Electron-dot formulas (must be paired if there are enough ve-)
- have much more negative charge than the covalently bonded atoms, thus BEND & CHANGE the shape of the compound.
Diatomic Elements
Hydrogen, then the Tetris 7 from G5-7
-H, N, O, F, Cl, Br, I
Naming Covalent Compounds
Prefixes are used for both nonmetals because two nonmetals can form 2+ different compounds. The second nonmetal has the suffix -ide.
Prefix-nonmetal + prefix-nonmetal-ide
Eg. NO : Nitrogen (mono)oxide
NO2 : Nitrogen dioxide
N2O: Dinitrogen oxide
N2O4: Dinitrogen tetraoxide
Reducing Common Factors in Covalent Compounds
IS NOT DONE!
Eg. N2O4
In Ionic compounds this formula would be reduced, but since these are nonmetals we NEED to know how many ve- are being shared.
Prefixes in Latin
1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca
Writing Chemical Formulas from Covalent Compound Names
1- write the symbols in the order of the elements in the name
2- write any prefies as subscripts
Steps to Writing Electron-dot Formulas
1- determine the arrangement of atoms (elements)
2- determine the ve-
3- attach each bonded atom to the central atom(s) w/pair of ve-
4- place remaining ve- as lone pairs to complete octets (excluding 2 for H atoms)
5- if octets are incomplete, form multiple bonds by converting a lone pair to a bonding pair
Electronegativity
The ability of an atom to attract bonding electrons of a covalent bond to itself.
Increases going up and across the PT
-F most electronegative element
Molecular Polarity
Unequal sharing of ve- exists when one element in a molecular formula has a higher electronegativity than another element in the formula.
Based on the difference of electronegativity of the elements of a compound, the type of bond can be predicted (nonpolar, polar, ionic)
Polar Covalent Bond
Unequal sharing of ve-
Determined by subtracting the difference between elements of a compound
0.5 - 1.7 = polar covalent bond
-denoted using the Greek delta, meaning ‘partial’ (delta + / delta -)
Nonpolar Covalent Bond
Equal or almost equal sharing of ve-
Determined by subtracting the difference between elements of a compound.
0.0 - 0.4 = nonpolar covalent bond
Ionic Bonds
Has an electronegativity difference of 1.8+
Occurs between metal+nonmetal
Result of a ve- transfer, not sharing
Predicting Bond Types
Nonpolar: 0.0 - o.4
Polar: 0.5 - 1.7
Ionic: 1.8+
The greater the electronegativity difference of 2 atoms, the more polar the bond.
The further away 2 atoms are on the PT, the more polar the bond.
Dipole Arrow
- |——->
The + of the arrow indicates the more positive atom (lesser electronegativity) while the arrow head points to the more negative atom (greater electronegativity drawing ve- towards it in a covalent compound)
