Unit 3 Part 2 - 2.2 The covalent model Flashcards
12APR25 (28 cards)
Rules of covalent bonds?
1. between nonmetals only
2. elements bond by sharing valence electrons
3. electronegativity difference is below 1.8
4. electrons are shared to obtain a complete octet
5. sharing of valence electrons leads to a variety of bonding combinations between the same
elements
6. octet rule because we are in the s + p block
7. need the prefix system
8. lower mp and bp
9. do not conduct electricity as well as ionic compounds
What are the diatomic elements?
H2 N2 O2 F2 Cl2 Br2 I2
Single bond features?
Share two electrons
- C -C
- Bonded pair
- Weakest and longest
Double bond features?
Share 4 electrons
- C - C
-
Triple bond features?
Share 6 electrons
C - C
-
-
- Strongest and shortest
How do covalent bonds form?
By atoms sharing electrons
Definition of covalent bonds?
The electrostatic attraction between a shared pair of electrons and the positively charged nuclei
What forms a molecule?
A group of atoms held together by a covalent bond
How are non-metals who react together able to achieve the stable electron structure of a noble gas?
By sharing electrons pair
In a covalent atom the nuclei of both atoms are attracted to what?
The shared pair of electrons
What can the octet rule be used for?
To predict stable arrangements of atoms in a covalent bond
What is the octet rule?
The tendency of atoms to gain a valence shell with 8 electrons
With the exception of WHAT, all elements of group 18 have a complete octet without the need to share electrons?
HELIUM
Why do group 18 halogens display low levels of chemical reactivity and do not tend to form covalent bonds w/other elements?
B/c they have a complete octet w/out the need of sharing electrons
What is an incomplete octet?
When small atoms form stable molecules In which the central atom has fewer than 8 electrons in its valence shell
Which elements can form incomplete octets?
- Hydrogen
- Beryllium
- Boron
- Aluminium
What is the most abundant gas in the air?
Nitrogen
Why is the nitrogen molecule very stable?
B/c the triple bond in N2 is difficult to break
How much of the atmosphere does nitrogen make up?
78%
Type of bonds in double bonds?
One sigma bond and one pi bond
Type of bonds in triple bonds?
One sigma bond and two pi bonds
What happens to the bonds as you go down a column?
Bond length increases
Bond enthalpy (strength) decreases
Which two elements can only form triple bonds?
Carbon and nitrogen
Which elements can form double bonds?
Carbon, Nitrogen, Oxygen, and Sulfur
